Non-native fishes inhabiting the streams and lakes of Illinois


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^• | APR 17 1996

^ ILLINOIS
NATURAL
HISTORY LIBKAKI

SURVEY _ .

Non-native Fishes Inhabiting

the Streams and Lakes of Illinois

Christopher A. Laird and Lawrence M. Page

Illinois Natural History Survey Bulletin

Volume 35, Article 1

March 1996





ILLINOIS
NATURAL
HISTORY
SURVEY

Non-native Fishes Inhabiting

the Streams and Lakes of Illinois

Christopher A. Laird and Lawrence M. Page
Center for Biodiversity

Illinois Natural History Survey

Illinois Natural History Survey Bulletin

Volume 35, Article 1

March 1996



Illinois Natural History Survey, Lorin I. Nevling, Chief

A Division of the Illinois Department of Natural Resources

A catalog of the publications of the Illinois Natural History Survey is available

without charge from the address below. A price list and an order blank are

included with the catalog.

Illinois Natural History Survey

Distribution Center

Natural Resources Building

607 East Peabody Drive

Champaign, Illinois 61820

Citation:

Laird, C.A., and L.M. Page. 1996. Non-native fishes inhabiting the streams and

lakes of Illinois. Illinois Natural History Survey Bulletin 35(1): 1-51.

Editor: Thomas E. Rice

US ISSN 0073-4918

Printed by Authority of the State of Illinois

(X41259-2M-3-96)



Contents

Acknowledgments iv

Introduction 1

Environmental Impacts of Non-native Fishes 3

The Identification of Non-native Fishes Found in Illinois 4

Key to Families of Fishes Found in Illinois 5

Petromyzontidae 7

Petromyzon marinus, sea lamprey 7

Clupeidae 9

Alosa pseudoharengus, alewife 1

Dorosoma petenense, threadfin shad 1

1

Cyprinidae 1

3

Cyprinus carpio, common carp 1

3

Carassius auratus, goldfish 15

Ctenopharyngodon idella, grass carp 16

Hypophthalmichthys molotrix, silver carp 18

Hypophthalmichthys nobilis, bighead carp 1

9

Scardinius erythrophthalmus, rudd 20

Cobitidae 22

Misgurnus anguillicaudatus, Oriental weatherfish 22

Osmeridae 23

Osmerus mordax, rainbow smelt 23

Salmonidae 25

Salmo salar, Atlantic salmon 26

Salmo trutta, brown trout 27

Oncorhynchus mykiss, rainbow trout 28

Oncorhynchus gorbuscha, pink salmon 29

Oncorhynchus tshawytscha, chinook salmon 30

Oncorhynchus kisutch, coho salmon 31

Atherinidae 33

Menidia beryllina, inland silverside 33

Gasterosteidae 34

Gasterosteus aculeatus, threespine stickleback 34

Moronidae 36

Morone americana, white perch 36

Morone saxatilis, striped bass 38

Gobiidae 40

Neogobius melanostomus, round goby 40

Literature Cited 41



Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Acknowledgments

Illustrations on pages 7, 10, 11, 13, and 15 are

reprinted from The Fishes of Illinois (Smith

1979). We are indebted to Craig W. Ronto for

the additional illustrations; to Dan Sallee for first

suggesting the project to us and reviewing the

manuscript; to Brooks M. Burr for allowing

access to records in the Fish Collection of

Southern Illinois University at Carbondale and

reviewing the manuscript; to Richard E. Sparks,

J. Ellen Marsden, and Robert J. Maher for

information on the distribution of exotic fishes in

Illinois; and to Thomas E. Rice for improving the

manuscript.



Introduction

At the turn of the century, only one non-native*

species of fish, the common carp, was estab-

lished in Illinois (Forbes and Richardson 1908).

In contrast, by 1979, six non-native fishes were

reproducing in Illinois (Smith 1979) and, in

1996, only 17 years later, seven more non-

native fishes have become established (Table

1). In addition to these 13 species, 9 non-native

fishes are periodically stocked in Illinois or

stray into the state from nearby states where

they are stocked (Table 1).

Because several of these fishes only

recently have become introduced or are

expanding their ranges in Illinois, they are not

familiar to most residents of the state. The keys

and descriptions in this publication are intended

to assist in the identification and monitoring of

the impacts of these 22 species. Also included

for each species is a brief summary of its

ecological and life history characteristics, and a

discussion of its Illinois distribution. Additional

information can be found in accounts by Smith

(1979) and by Burr (1991), who reviewed

various aspects of recent changes in the fish

fauna of Illinois.

"A non-native species is defined as one that did not occur in

Illinois historically; an established non-native is one that

now lives and reproduces in Illinois waters as a result of

human influence. Two species, the white catfish (Ameiurus

catus) and the Rio Grande cichlid (Cichlasoma

cyanoguttatum), were once considered established but are

no longer thought to be reproducing in Illinois (Smith

1979; Burr 1991).



Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Table 1. Non-native fishes in Illinois.

Species established by 1979 Additional species

established by 1996

Other species periodically released

in Illinois or nearby states

sea lamprey,

Petromyzon marinus

grass carp,

Ctenopharyngodon idella

silver carp,

Hypophthalmichthys molotrix

alewife,

Alosa pseudoharengus

bighead carp,

Hypophthalmichthys nobilis

rudd,

Scardinius erythrophthalmus

threadfin shad,

Dorosoma petenense

Oriental weatherfish,

Misgurnus anguillicaudatus

rainbow trout,

Oncorhynchus mykiss

rainbow smelt,

Osmerus mordax

inland silverside,

Menidia beryllina

coho salmon,

Oncorhynchus kisutch

common carp,

Cyprinus carpio

threespine stickleback,

Gasterosteus aculeatus

chinook salmon,

Oncorhynchus tshawytscha

goldfish,

Carassius auratus

white perch,

Morone americana

pink salmon,

Oncorhynchus gorbuscha

round goby,

Neogobius melanostomus

brown trout,

Salmo trutta

Atlantic salmon,

Salmo salar

striped bass,

Morone saxatilis



Environmental Impacts of

Non-native Fishes

None of the introduced fishes has enhanced the

plight of a native species or a natural aquatic

ecosystem in Illinois and, thus, none can be

said to have had a beneficial environmental

impact. Instead most, and perhaps all, can be

shown to have had negative environmental

impacts.

Perhaps best known is the negative

impact of the parasitic sea lamprey on native

fishes of Lake Michigan. The sea lamprey was

introduced from Atlantic Slope drainages into

Lake Michigan in the 1930s and led to dramatic

declines in the native, commercially valuable

lake trout and other salmonids. Another

familiar example of environmental degradation

caused by an introduced species was the

pollution of Lake Michigan beaches by the

massive die-offs of alewives, another intro-

duced Atlantic Slope species, in the 1960s.

Environmental damage caused by other

introduced species is less visible and less

known but perhaps only because the extent of

their damage has yet to be understood. Non-

native species compete with related or ecologi-

cally similar native species for food, spawning

areas, and other limited resources. For ex-

ample, the bighead carp and silver carp, only

recently introduced into North America from

Eurasia, feed on plankton, food of the larvae of

all native fishes and all native mussels. If these

two species of carp become common in Illinois,

they may significantly reduce populations of

native species by limiting successful reproduc-

tion.

Non-native species may alter the habitat

in ways that make it unsuitable for native

species. For example, the common carp,

another transplant from Eurasia, destroys

vegetation and increases water turbidity by

rooting in the substrate, causing a loss of

habitat for species requiring vegetation and

clear water. The grass carp was brought to

North America from Asia to feed on plants in

farm ponds and other water bodies where an

abundance of vegetation is considered a

problem. However, populations of many native

stream- and lake-inhabiting plants already are

being depleted because of excessive siltation

resulting from poor agricultural practices and

the use of herbicides. Silt smothers the plants,

and herbicides poison them. In addition to the

lamentable loss of the vegetation itself, many
fishes and other aquatic animals are dependent

on aquatic plants as places to hide, to spawn,

and to find food. Several fishes now extirpated

from Illinois, and several threatened and

endangered fishes (e.g., the bigeye chub,

bigeye shiner, starhead topminnow, and banded

killifish) are those that are strongly dependent

upon vegetation for survival, and it is apparent

that their loss is due at least in part to the loss

of aquatic vegetation. The grass carp is going

to make their survival in Illinois even more

difficult. Many species of waterfowl are

heavily dependent on aquatic vegetation for

food, and their habitats also are negatively

affected by the common and grass carps.

Non-native fishes can have negative

impacts by feeding on native species. For

example, two recent arrivals in Illinois, the

threespine stickleback and the round goby, are

known to feed on the eggs and larvae of fishes,

including sport fishes. The various species of

Pacific salmon being stocked in Lake Michi-

gan, and the striped bass, occasionally stocked

in southern Illinois, are acquired because they

are large sport fishes of interest to anglers.

However, as adults they feed on native fishes,

including threatened and endangered species

and native species also considered desirable as

sport fishes, such as sunfishes and basses.

Even introductions considered from

economic and recreational perspectives to be

successful carry with them environmental and

economic tradeoffs. Introductions rarely fulfill

the hyperbole that accompanies them, and most

damage the environment or result in an

economic cost, or both. While the number of

non-native species has been increasing in

Illinois, the number of native fishes has

declined from 1 87 species at the turn of the

century (Forbes and Richardson 1908) to only

174 today. The loss of 13 species was due to a

large number of factors relating to environmen-

tal degradation, probably including the intro-



Illinois Natural History Survey Bulletin Vol. 35 Art. 1

ductions of exotic fishes. The general environ-

mental impact of each introduced species is

discussed in the next section.

Four of the 13 established non-native

fishes—sea lamprey, alewife, threespine

stickleback, and white perch—reached Illinois

accidentally as the result of the Welland Canal,

built in the 1 820s to bypass Niagara Falls and

connect Lake Ontario with Lake Erie. Two
established species, the goldfish and Oriental

weatherfish, escaped accidentally from ponds

or were released by aquarists. One species, the

round goby, arrived accidentally in the same

manner as the zebra mussel (Dreissena

polymorpha)—in ship bilge water. The

remaining six species were brought to Illinois

deliberately in an effort to improve fishing:

common carp, grass carp, bighead carp,

threadfin shad, rainbow smelt, and inland

silverside. The six salmonids in Lake Michi-

gan also have been stocked there in an effort to

improve fishing.

The Identification of Non-native

Fishes Found in Illinois

Keys are provided for the identification of non-

native fishes found in Illinois. A key to the

families of fishes appears first and leads the

reader to the page where a key to species of a

particular family is found. The family key

includes native as well as introduced families.

The keys to species include native species that

are related or are similar in appearance and

likely to be confused with introduced species.

The keys are written as supplements to keys

published in Smith's (1979) The Fishes of

Illinois, and some parts of Smith's keys are

reprinted verbatim. Non-native fishes can be

identified with the following keys; however, if

you suspect that the fish you are attempting to

identify is a native species, you should consult

Smith (1979). Species names in bold print are

those of non-native fishes established or

commonly found in Illinois; family names in

bold print are those families that contain

established or stocked species.

For some identifications, it will be best to

begin with the family key and work your way

through to the species. However, if you know

from past experience that the fish you are

working with is one of a few species (e.g., a

shad), you can begin with a key to species.

Diagnostic counts given are those that are

useful in separating closely related species.

Lateral-scale counts (often referred to else-

where as lateral-line scale counts) refer to the

number of scales along the lateral line if the

lateral line is present and complete, or along the

mid-side if the lateral line is absent or incom-

plete. Maximum and common lengths are total

(rather than standard) lengths.



March 1996 Non-native Fishes

Key to Families of Fishes Found in

Illinois

(Those families in bold print contain non-native

species)

1. Mouth without jaws; pectoral and pelvic fins

absent; 7 gill openings on each side

(lampreys) Petromyzontidae (p. 7)

Mouth with jaws; pectoral fins always

present, pelvic fins usually present; 1 gill

opening on each side of head 2

2. Dorsal fin single (i.e., of soft rays only) and

extending more than half of body length;

anterior nostrils tubular 3

Dorsal fin single or double (2 fins, first with

spines); if single, extending much less

than half of body length; anterior nostrils

not tubular 4

3. Dorsal, caudal, and anal fins continuous;

scales tiny, deeply imbedded; body

snakelike (eels) Anguillidae

Dorsal, caudal, and anal fins not continuous;

scales large; body stout, more fishlike

(bowfins) Amiidae

4. Caudal fin heterocercal (vertebral column

flexed upward into caudal fin) 5

Caudal fin homocercal (vertebral column not

flexed upward into caudal fin) 7

5. Caudal fin rounded; snout a bony, strongly

toothed beak; body completely covered

with scales (gars) Lepisosteidae

Caudal fin forked; snout not a bony, strongly

toothed beak; body not completely scaled

6

6. Snout long and paddle-shaped; without bony

scutes (paddlefishes) .... Polyodontidae

Snout cor ical or shovel-shaped; large bony

scutes on head and along back and sides

(sturgeons) Acipenseridae

7. One set of paired fins (pectorals); eyes very

small (cavefishes) Amblyopsidae

Two sets of paired fins (pectorals and

pelvics); eyes variable 8

8. Adipose (unrayed fatty) fin present 9

No adipose fin 12

9. Large barbels present around mouth (cat-

fishes) Ictaluridae

No barbels 10

10. First 1 or 2 rays of dorsal and anal fins

spiny; scales strongly ctenoid and rough

to the touch; small, rather translucent

fishes (trout-perches) Percopsidae

All fin rays soft; scales cycloid and smooth

to the touch; usually large, darkly

pigmented fishes 11

1 1. No pelvic axillary process; lower jaw

strongly projecting beyond upper; usually

70 or fewer scales in lateral line; con-

spicuously enlarged teeth on jaws and

tongue (smelts) Osmeridae (p. 23)

Axillary process at base of pelvic fin; jaws

equal or lower jaw slightly projecting;

usually more than 70 scales in lateral

line; teeth not conspicuously enlarged

(trout, salmon, whitefishes)

Salmonidae (p. 25)

12. Body elongate; 5 pairs of barbels around

mouth (loaches) Cobitidae (p. 22)

Body variable; 1 pair, a single, or no

barbels around mouth 13

13. Conspicuous median barbel near tip of

chin; dorsal and anal fins each with 60 or

more rays (codfishes) Gadidae

No median barbel near tip of chin; dorsal

and anal fins each with fewer than 35

rays 14

14. Anus between gill membranes (except in

small young, which have anus farther

back, but well in front of anal fin) (pirate

perches) Aphredoderidae

Anus situated just in front of anal fin . . . 15



Illinois Natural History Survey Bulletin Vol. 35 Art. 1

15. Anterior dorsal fin represented by 2 to 9

spines not connected, or barely connected

to one another by membranes (stickle-

backs) Gasterosteidae (p. 34)

Dorsal fin without isolated, unconnected

spines 16

16. One dorsal fin with no more than 3 spiny

rays 17

One or 2 dorsal fins; if 1, anterior portion

with more than 3 spiny rays 25

17. Dorsal fin with large stout spine (goldfish

and introduced carp species)

Cyprinidae (p. 13)

Dorsal fin without sharp spine 18

18. Head scaleless 19

Head partly or entirely scaled 22

19. Axillary process at base of pelvic fin;

conspicuous adipose eyelid 20

No pelvic axillary process; no adipose

eyelid 21

20. Midline of belly with sawtoothed edge;

dorsal fin base situated well anterior to

anal fin base; lateral line absent (herrings,

shads) Clupeidae (p. 9)

Midline of belly without sawtoothed edge;

dorsal fin base situated partly or entirely

over anal fin base; lateral line present

(mooneyes) Hiodontidae

21. Lips thickened, striate, and papillose

(except in buffalos); anal fin usually

situated posteriorly, its adpressed rays

reaching, or almost reaching, caudal fin

base; 10 or more dorsal rays (except in

creek chubsucker, which has a sucking

mouth and no lateral line) (suckers) ....

Catostomidae

Lips thin (except in suckermouth minnow);

anal fin usually situated farther forward,

its adpressed rays far short of caudal fin

base; 9 or fewer dorsal rays (minnows). .

Cyprinidae (p. 13)

22. Caudal fin forked; snout duckbeak-like;

jaws with large canine teeth; scales small,

more than 90 in lateral series (pikes) ....

Esocidae

Caudal fin rounded; snout not duckbeak-

like; jaws without canine teeth; scales

large, fewer than 50 in lateral series . . 23

23. Mouth terminal; no groove between snout

and upper lip; pelvic fins originate closer

to caudal fin base than to tip of snout

(mudminnows) Umbridae

Mouth upturned; upper lip separated from

snout by deep groove; pelvic fins closer

to tip of snout than to caudal fin base . . .

24

24. Body with bars or stripes; anal fin of male

without elongated anterior rays and not

modified as an intromittent organ; body

with bars or stripes (topminnows)

Fundulidae (previously

Cyprinodontidae)

Body without bars or stripes; anal fin of

male with elongated anterior rays and

modified as an intromittent organ; body

without bars or stripes (mosquitofishes)

Poeciliidae

25. Pelvic fins fused to one another (gobies) . .

Gobiidae (p. 40)

Pelvic fins separate 26

26. Body unsealed; 4 or fewer pelvic rays

(sculpins) Cottidae

Body scaled; 5 or more pelvic rays .... 27

27. Large gap between small anterior and large

posterior dorsal fins; origin of pelvic fin

well behind origin of pectoral fin

(silversides) Atherinidae (p. 33)

Dorsal fins continuous or separated by

narrow gap; origin of pelvic fin under or

slightly behind origin of pectoral fin . . .

28



March 1996 Non-native Fishes

28. Lateral line extends to end of caudal fin;

base of first dorsal fin about half as long

as base of second dorsal fin (drums) ....

Sciaenidae

Lateral line, if present, not continued to end

of caudal fin; base of first dorsal fin more

than half length of second dorsal fin base

29

29. Three or more anal spines; body deep and

slab-sided 30

One or 2 anal spines; body usually more or

less fusiform (perches and darters)

Percidae

Petromyzontidae

Key to adult lampreys

1 . Prominent black mottling on body and fins;

2 dorsal fins separated at base; to 120 cm
(47 in.) (sea lamprey)

Petromyzon marinus

No prominent dark mottling (body dark

olive above, light below); slightly

notched dorsal fin or 2 dorsal fins joined

at base; to 39 cm (15.5 in.)

native lampreys

30. Large spine on rear edge of gill cover;

sawtoothed edge on preopercle (temper-

ate basses) Moronidae (p. 36)

No spine on gill cover; smooth-edged

preopercle (sunfishes) .... Centrarchidae

Petromyzon marinus, sea lamprey

Figure 1

Origin and Range

The sea lamprey is native to the Atlantic

Ocean and Lake Ontario. The 1820 construc-

tion of the Welland Canal allowed this and

other migratory fishes to bypass Niagara Falls

and move from Lake Ontario to the western

Great Lakes. The sea lamprey was first found

in Illinois in 1936 attached to a lake trout from

Lake Michigan (Hubbs and Pope 1937). Sea

lampreys were so abundant in Lake Michigan

during the 1940s and 1950s that they caused

serious damage to the fishing industry (Shetter

1949). During the 1960s the sea lamprey

population was reduced, at least in part,

through the use of a chemical pesticide that

kills lamprey larvae. This species is still

present in Lake Michigan, but in reduced

numbers.

Biology

The life history of the sea lamprey was

described in detail by Applegate (1950). Great

Lakes sea lampreys leave their lake only during

the spawning season. Newly transformed



Illinois Natural History Survey Bulletin Vol. 35 Art. 1

adults migrate to deep, offshore areas of the

lake during fall, winter, and early spring and

remain until late summer, when they move to

shallow water. They remain in shallow water

until the next spring, when upstream migration

occurs (Applegate 1950). Mature adults stop

feeding prior to migration, and the digestive

system atrophies. Adults die after spawning;

consequently, the adult sea lamprey lives for 1-

1.5 years.

Lampreys can travel long distances,

commonly moving between lakes. One tagged

individual was recaptured 628 km (393 mi)

from its point of release (Moore et al. 1974).

Sea lampreys are known to attach to the hulls

of ships, further facilitating their movement.

The habitat of the stream-dwelling ammocoetes

consists of shallow areas with a sand/silt

substrate for the first two years and deeper

areas of the stream with a silt and detritus-

covered bottom after two years (Manion and

McLain 1971). Ammocoetes burrow into the

substrate and filter feed, with only the oral

hood protruding from the substrate (Applegate

1950). Diet consists of diatoms shortly after

hatching and filamentous green algae, detritus,

pollen, diatoms, desmids, and protozoans as

ammocoetes (Creaser and Hann 1929). Adults

are parasitic and feed by attaching to other

fishes with the oral sucking disk, rasping a

wound into the host and consuming body

fluids. A secretion from the buccal glands

helps prevent blood coagulation in the host and

digests muscle to the point that it can be

ingested by the lamprey (Scott and Crossman

1973). There is some evidence that fishes with

soft scales, such as the lake trout, are preferred

to those with harder scales.

Spawning usually occurs from May to

July. Migration begins once the water tempera-

ture in the stream reaches 4.4°C (40°F), and sea

lampreys may be present at the spawning site

for 6-8 weeks before spawning activity begins.

Migration ends when the lampreys reach

shallow areas with a gravel substrate and strong

current. Upstream runs can be as long as 1 8

1

km (121 mi), but are usually considerably

shorter (Norman 1979). Spawning activity

begins when water reaches a temperature of

10°C (50°F) and peaks at 16°C (61°F). Prior to

spawning, a circular nest is constructed by

removal of gravel with the sucking disk. The

nest is usually constructed in a riffle or at its

upstream margin in water that is 38-61 cm deep

(15-24 in.) (Scott and Crossman 1973). Early

in the season the male begins the construction

but later, when males are more scarce, the

female may initiate nest construction activity

(Applegate 1950). Most nests are about 45 cm
X 40 cm (17.7 in. X 15.7 in.), but often they are

so close together that they are effectively joined

and can extend for several meters (Manion and

McLain 1971). During the spawning act the

female attaches her sucking disk to a rock at the

upstream end of the nest, the male attaches his

sucking disk to her back, slightly behind the

head, and wraps his body around her. The

female vibrates while eggs and milt are

released (Scott and Crossman 1973). Spawning

continues for 16-48 hours, during which 20-40

eggs are released at intervals of 1-10 minutes

(Applegate 1950). Most matings consist of one

male and one female that remain paired

throughout the spawning period, but other

combinations, especially of multiple females

with one male, are observed later in the season

when males are outnumbered by females

(Applegate 1950). The adhesive eggs are

carried to the downstream end of the nest and

covered by sand and gravel, which are stirred

up by additional nest-building activities of the

adults. The number of eggs released per female

ranges from 24,000 to 107,000 (Becker 1983)

and averages of 62,870 and 68,599 have been

reported (Vladykov 1951; Manion 1972).

Average numbers of larvae found in nests

utilized by one pair of adults ranged from 2,627

to 4,029 (Manion 1968).

Eggs range from 0.8 to 1.3 mm in

diameter and hatch in 11-14 days. The

ammocoete stage is usually reached after 17-33

days (Manion and McLain 1971).

Ammocoetes are typically found in areas with a

soft substrate at least 10 cm (4 in.) thick

(Applegate 1950). A study on the Big Garlic

River in Michigan reported the following

lengths at each age for larval lampreys: 1.3 cm
(0.5 in.) at year 0, 3.9 cm (1.5 in.) at year 1, 6.3



March 1996 Non-native Fishes

cm (2.5 in.) at year 2, 8.0 cm (3.1 in.) at year 3,

9.2 cm (3.6 in.) at year 4, and 10.7 cm (4.2 in.)

at year 5 (Manion and McLain 1971 ). Growth

was considerably slower after this point with a

size of 12.9 cm (5.1 in.) at 12 years (Manion

and Smith 1978). Low ammocoete density and

increasing stream size were both positively

correlated with faster growth. Some movement

took place before metamorphosis, but several

ammocoetes had not moved more than a few

meters in 5 years. Transformation of larvae into

adults can begin in as few as 5 years (Manion

and McLain 1971), although Stauffer (1962)

found a minimum of 7 years. In the Garlic

River some ammocoetes had not metamor-

phosed after 17 years (Becker 1983). Newly

transformed adults range in length from 9.5 to

24.3 cm (3.7-9.6 in.) (Applegate et al. 1961)

and average 14.0 cm (5.5 in.) (Manion and

Stauffer 1970). The maximum size of the sea

lamprey is 120 cm (47 in.); adults commonly

reach 50 cm (20 in.).

Diagnostic Counts

Usually 66-75 trunk myomeres; 2

supraorbital teeth; usually 2-2-2-2 lateral

circumoral teeth; 8-10 posterior circumoral

teeth; 7-8 infraoral teeth.

Expansion

It is unlikely that the range of the sea

lamprey in Illinois will expand beyond Lake

Michigan.

Impact on Illinois

The sea lamprey contributed to a major

decline in several native salmonids in Lake

Michigan, especially the lake trout, Salvelinus

namaycush, and the cisco, Coregonus artedii.

Populations of native fishes, as well as the Lake

Michigan commercial fishing industry, may

never recover to prelamprey levels. Presently

the sea lamprey population is controlled

through the use of chemical pesticides that have

varying effects on other organisms. The

walleye, Stizostedion vitreum, is almost as

susceptible to the most common lampricide (3-

triflouromethyl-4-nitrophenol [TFM]) as is the

sea lamprey (Becker 1983). Lieffers (1990)

found that 88% of invertebrate populations

sampled decreased in number after the applica-

tion of TFM, although they seemed to recover

within a few months. Bills and Johnson (1992)

showed that the toxicity of TFM increased with

decreasing pH, possibly resulting in mortality

of nontarget species. The continued control of

the sea lamprey, while necessary, will probably

have detrimental effects on other organisms.

Clupeidae

Key to herrings and shads

1

.

Last ray of dorsal fin not elongated; pectoral

fin not extending to pelvic fin origin; 18

or fewer anal rays 2

Last ray of dorsal fin of adult elongated into

a filament; pectoral fin extending

posteriorly to or beyond pelvic fin origin;

19 or more anal rays 4

2. Lower jaw projecting far beyond snout; 20-

24 rakers on lower limb of first gill

arch (skipjack herring)

Alosa chrysochloris

Lower jaw equal to or projecting only

slightly beyond snout; 39 or more rakers

on lower limb of first gill arch 3

3. Cheek decidedly deeper than long; 42-48

rakers on lower limb of first gill arch; no

jaw teeth (Alabama shad)

Alosa alabamae

Cheek longer than deep; 39-41 rakers on

lower limb of first gill arch; teeth on

lower jaw (alewife)

Alosa pseudoharengus

4. Terminal mouth; rounded snout; 40-48

lateral scales; 17-27 anal rays (threadfin

shad) Dorosoma petenense

Subterminal mouth; blunt snout; 52-70

lateral scales; 25-36 anal rays (gizzard

shad) Dorosoma cepedianum



10 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Alosa pseudoharengus, alewife

Figure 2

Origin and Range

The alewife is native to the Atlantic

Ocean and streams of the Atlantic coast of

North America. This species was found in

Lake Michigan in 1949 and became extremely-

abundant there in the 1950s and 1960s after

populations of native predators had been

severely reduced by the sea lamprey. The

alewife population declined subsequent to the

introduction of several large predaceous salmon

and trout into Lake Michigan. Presently,

alewives are common in Lake Michigan but are

not as abundant as they were during the 1950s.

This species is not found elsewhere in Illinois.

Biology

Alewives are anadromous in their native

range, but Illinois populations reproduce in the

main body of Lake Michigan. Anadromous

populations form schools that usually remain

close to the natal estuary (Mansueti and Hardy

1967). Both anadromous and landlocked

populations inhabit open water during most of

the year. Alewives remain offshore during the

day and move to shallower water at night.

Threinen (1958) observed schools of alewives

in Lake Michigan that were 4.5-6 m (15-20 ft)

in diameter containing 5,000-6,000 individuals.

Graham (1957) described schooling behavior of

Lake Ontario alewives while inshore. He
observed a "roller-coaster" movement in which

the school undulates from the surface to the

bottom and back, often breaking the surface.

"Milling" behavior occurs when the school

forms a circle, usually at an indentation of the

shoreline or an isolated object in the water.

Lake Michigan studies indicate that

zooplankton, especially copepods and cladocer-

ans, compose the diet of juveniles and adults

found at depths less than 9.1 m (30 ft) (Morsell

and Norden 1968; Norden 1968). Adults found

at greater depths fed mostly on the amphipod

genus Pontoporeia (Morsell and Norden 1968).

Scales have been found in the stomachs of

alewives as well as the eggs of conspecifics and

other species (Edsall 1964; Morsell and Norden

1968). Schools of alewives have been ob-

served feeding on insects at the surface at dusk

in Lake Ontario (Graham 1957), and Odell

(1934) observed alewives leaping from the

water to catch insects.

Movement towards spawning grounds

usually begins in late April or early May. In

Lake Michigan, spawning has been reported as

early as June 24 (Edsall 1964) and as late as

August 24 (Norden 1967). Spawning occurs at

night over sand or gravel (Scott and Crossman

1973). Water depth ranges from a few inches

(Rothschild 1962) to 10 ft (Edsall 1964).

Spawning usually occurs in sluggish water but

has been observed in fast water over gravel

(Greeley 1935). During the spawning act, two

or more fish swim in tight circles with their

sides touching while spiraling upward towards

the surface and then down again (Edsall 1964).

Most adults leave the spawning area soon after

spawning (Graham 1956). Fecundity was

estimated to range from 10,000 to 12,000 for

landlocked females (Odell 1934) and from

60,000 to 100,000 for anadromous females

(Scott and Crossman 1973). From a Michigan

spawning, Edsall (1964) reported consumption

of large numbers of eggs by spottail shiners

{Notropis hudsonius) and juvenile alewives.

Bigelow and Welsh (1925) reported swarms of

young white perch following spawning

alewives and devouring the eggs.

Mansueti and Hardy (1967) described the

development of eggs and fry. They reported

fertilized eggs of 0.94-1.25 mm in diameter and

an incubation time of 3-5 days at 20°C (68°F).

Male alewives mature earlier and die earlier

than females (Becker 1983). In Lake Ontario,

Graham (1956) found females up to 8 years

old, but no males older than 5 years were

collected. Norden (1967) reported the follow-

ing mean total lengths for Lake Michigan

alewives: 13.9 cm (5.5 in.) at 1 year, 15.8 cm



March 1996 Non-native Fishes II

(6.2 in.) at 2 years, 17.3 cm (6.8 in.) at 3 years,

and 19.3 cm (7.6 in.) at 4+ years. Most

alewives first reproduce at 2 or 3 years.

The alewife is known to undergo periodic

population die-offs in the Great Lakes. The

causes of these die-offs are not entirely clear.

Most authors attribute the die-offs to intoler-

ance of changing temperatures (Graham 1956;

Becker 1983). Hoar (1952) suggested that

alewives may lose osmotic control in fresh

water as a result of an exhausted thyroid

mechanism. Smith (1968) suggested that the

alewife cannot tolerate the cold temperatures of

the Great Lakes during the winter. The

maximum size of the alewife is 38.1 cm (15 in.)

but Great Lakes individuals seldom exceed 20

cm (7.9 in.).

Diagnostic Counts

39-41 rakers on lower limb of first gill

arch; 12-16 dorsal rays; 15-19 anal rays.

Expansion

The distribution of alewives in Illinois is

not expected to expand beyond Lake Michigan.

Impact on Illinois

In the late 1960s, massive die-offs of

alewives occurred causing nuisance conditions

near the shores of the lake. Alewives have

contributed to the decline of several native

planktivorous salmonids of Lake Michigan and

are believed to have adversely affected popula-

tions of other fishes as well, including the

emerald shiner (Notropis atherinoides) and the

yellow perch (Perca flavescens). The alewife

is commercially harvested in northern Lake

Michigan on a small scale for use as fertilizer

and pet food (Becker 1983).

Dorosoma petenense, threadfin shad

Figure 3

Origin and Range

The threadfin shad is native to the

streams of the southern U.S., Mexico, and

Central America. It was introduced to several

Tennessee Valley Authority reservoirs during

the 1940s and 1950s and later to many of the

large reservoirs of the southwestern U.S. This

species spread north and was first found in

Illinois in 1957 (Smith 1979). By 1979 it was

established and commonly captured in the Ohio

River and was present in other streams in

extreme southern Illinois. In recent years the

threadfin shad has spread further and has been

captured from several sites on the Illinois

River, sometimes in high numbers (Rip Sparks,

pers. comm.).

Biology

The threadfin shad is an open-water filter

feeder and often feeds in large schools over

sand or mud. The schools are often composed

only of one year-class of fish (Berry et al.

1956). Threadfin shad are usually found in

schools over deep water, but small schools and

individuals are sometimes found near the shore.

Threadfin shad are sensitive to low tempera-

tures, and population die-offs often occur after

a temperature drop. Laboratory experiments

indicate that schools begin to break up and

feeding activity decreases at temperatures

below 9°C (48.2°F); a temperature of 4°C

(39.2°F) is fatal (Griffith 1978).

Algae is an important component of the

diet of threadfin shad with studies reporting

that it averages 16.4-54.1% of the diet (Haskell

1959; Miller 1967). In an Arkansas study,

Miller (1967) found that the animal portion of

the diet (45.9%) consisted of all major groups



12 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

of plankton as well as dipteran larvae and adult

insects. The diets of young-of-the-year and

age-1 individuals were the same and no

evidence of selective feeding was found.

However, Kimsey (1958) did find selectivity

for the eggs of the gulf croaker (Bairdiella

icistius) in a coastal California study. In an

Arizona study, crustaceans composed 7.5% of

the diet (Haskell 1959). In addition to pelagic

feeding, the threadfin shad commonly feeds

from the bottom as evidenced by the presence

of mud, sand, and bits of wood in the gut of

most individuals collected (Miller 1967;

Haskell 1959). Haskell (1959) found algae to

be the most common food item during the

winter and animal matter prevalent in the diet

during the spring and summer. Foods reported

only in small quantities include filamentous

algae, blue-green algae, eggs of invertebrates,

and aquatic nematodes (Haskell 1959).

Threadfin shad usually spawn from early

April to August at water temperatures of 14.4-

27.2°C (60-8 1°F). Johnson (1971) reported

different spawning peaks for different year-

classes of fish in an Arizona reservoir study.

Age 3 and 4 fish became ripe on April 1 and

peaked on April 10, age 2 fish became ripe on

April 25 and peaked during early May, and age

1 fish became ripe during mid-April and

peaked in late May. Spawning begins at dawn

and terminates shortly after sunrise. In Tennes-

see, spawning usually took place between 5:30

and 7:30 a.m. (McLean et al. 1982). Johnson

also reported that older shad may sometimes

spawn more than once during a season, but that

age threadfin shad did not spawn. Some have

suggested that age fish may spawn late in the

season (Berry et al. 1956; Smith 1979).

Lambou (1965) and Kimsey (1964) observed

spawning of threadfin shad in Louisiana and

California. They reported one or more females

swimming in a loose school with several males

in attendance. This group swam near the

surface and rushed rapidly to an object project-

ing above the water, or slightly below the

surface, and released gametes. The shad often

break the surface of the water as the adhesive

eggs are released. Eggs adhere to submerged

plants, pilings, and other objects. Berry et al.

( 1 956) reported evidence of occasional mass-

spawning mortality. This was not associated

with temperature fluctuations and does not

seem to be typical. Kimsey (1964) reported

mortality of threadfin shad that spawned near

shore resulting from some of them being

stranded during spawning activities. Johnson

( 1 97 1 ) found an average of 2,308 eggs per

gram of ovary and estimated average fecundity

for each year class. Estimated averages range

from 923 to 1,616 for age 1 fish and 1,616 to

3,924 for age 2 fish. Up to 25,000 eggs per

female were reported from an Arkansas

reservoir (Kilambi and Baglin 1969). Some

females may be able to spawn more than once

per season causing yearly fecundity estimates

to be too low. Johnson (1971) also found some

individuals whose gonads were filled with fatty

tissue and gender was indeterminable. This

phenomenon was more common in large

individuals with about 77.3% of the fish over

9.9 cm (3.9 in.) having fatty tissue in the

gonads.

Eggs are 0.75 mm in diameter. Labora-

tory studies show a maximum incubation

temperature of 34.2°C (93.5°F) and a minimum

of 15°C (59°F) (Hubbs and Bryan 1974).

Threadfin shad generally do not live longer

than 4 years and most do not live longer than 2

years. Johnson (1970) found that most of the

largest fish were females, resulting from higher

male mortality rather than faster female growth.

Sexual maturity may sometimes be reached in

less than 1 year (Smith 1979), although most

researchers found no evidence of this. Maxi-

mum size is 23 cm (9 in.); adults seldom

exceed 13 cm (5 in.) in fresh water and 19 cm
(7.5 in.) in salt water.

Diagnostic Counts

40-48 lateral scales; 10-14 dorsal rays;

17-27 anal rays.

Expansion

Threadfin shad have infiltrated the large

rivers of the southern half of the state and are

present in the Illinois River. Their intolerance

of cold probably will prevent them from

becoming common in northern Illinois.



March 1996 Non-native Fishes 13

Impact on Illinois

Threadfin shad often are stocked in

reservoirs as forage for large predators. This

species feeds on plankton and is very prolific,

giving it the potential to deplete populations of

plankton. Other plankton-feeding fishes,

including the larvae of all native fishes, can be

adversely affected.

dorsal rays; 10-1 1 anal rays; 10-13 rakers

on first gill arch; pharyngeal teeth 3,5-5,3

(rudd) . . . Scardinius erythrophthalmus

Cyprinus carpio, common carp

Figure 4

Cyprinidae

Key to introduced minnows and the golden

shiner, which is similar in appearance to the

rudd.

1. Dorsal fin long, 15-21 rays 2

Dorsal fin short, 8- 1 1 rays 3

2. Conspicuous barbels around mouth; 32-37

lateral scales (common carp)

Cyprinus carpio

No barbels; 26-30 lateral scales (goldfish) . .

Carassius auratus

3. Keel between anal and pelvic fin bases ... 4

No ventral keel (grass carp)

Ctenopharyngodon idella

4. More than 85 lateral scales 5

Fewer than 55 lateral scales 6

5. Ventral keel extending from anus to isthmus

between gill covers; gill rakers fused into

porous plate; sides of body plain (silver

carp) .... Hypophthalmichthys molotrix

Ventral keel extending from anus to pelvic

fin base; gill rakers comblike; sides of

body covered with small dark blotches

(bighead carp)

Hypophthalmichthys nobilis

6. No scales on keel; clear to orange fins; no

black on tail; usually 7-9 dorsal rays;

11-14 anal rays; 17-19 rakers on first gill

arch; pharyngeal teeth 0,5-5,0 (golden

shiner) Notemigonus crysoleucas

Scaled keel; red fins; anterior portion of

caudal fin with black rays; usually 9-11

Origin and Range

Native to Eurasia, the common carp first

arrived in North America in 1831 and is now
widely distributed. It was distributed through-

out Illinois by the time of Forbes and

Richardson's (1908) survey of Illinois fishes

and was described as abundant in all parts of

the state by Smith (1979). It remains common
in most areas of Illinois.

Biology

The common carp is an omnivorous

benthic feeder that is most abundant over silt or

clay, often near vegetation. It can be found in

almost any type of habitat but prefers warm
sluggish waters of streams and lakes. Common
carp are very tolerant of high turbidity and low

oxygen levels. This species is able to utilize

atmospheric oxygen (MacKay 1963) and is

often one of the few species able to persist in

highly degraded streams.

Common carp feed most heavily at 20°C

(68°F) and almost cease to feed below 8°C

(46.4°F) (Muus and Dahlstrom 1971). Com-
mon carp frequently forage by sucking up

bottom ooze and expelling it to expose food

items (Moyle 1976), thereby increasing the

turbidity of waters that they inhabit. The diet

consists of a variety of foods including insect

adults and larvae, crustaceans, mollusks, fishes,

bottom ooze, worms, and plant material. The



14 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

proportions of these foods in the diet vary

among populations. For most populations

insect larvae and other benthic invertebrates are

the principal components of the diet. Plant

matter was reported to compose as much as

43.5% of the diet in a New Mexico study

(Jester 1974) and as little as 2.8% of the diet in

a study conducted in Wisconsin (Pearse 1918).

Other components vary in the diet depending

on environmental availability. A recent report

documented the presence of large quantities of

lake trout eggs and zebra mussels in the

stomachs of common carp captured near a

breakwater at the southern end of Lake

Michigan (Marsden 1993).

In Illinois, spawning takes place from

spring to early summer (Smith 1979). Swee

and McCrimmon (1966) reported on reproduc-

tive biology in Ontario. Spawning begins when

water temperature reaches about 17°C (62.6°F)

and ceases when water reaches 26°C (78.8°F)

(Scott and Crossman 1973). Common carp

congregate in large numbers and spawn in

shallow water, often with the backs of large

individuals protruding from the surface. In

Illinois spawning frequently takes place in

flooded cornfields (Sigler 1958). From one to

several males attend each female as she

broadcasts her eggs over the substrate (Becker

1983). The eggs are adhesive and become

attached to vegetation and debris found in the

spawning area. Females produce enormous

numbers of eggs, which may account for as

much as one-third of the female's weight

(Muus and Dahlstrom 1971). Swee and

McCrimmon (1966) reported a range of 36,000

eggs, from an age 4 female of 39.4 cm (15.5

in.) to 2,208,000 eggs in an age 16 female of

85.1 cm (33.5 in.) and 10.1 kg (22.3 lb).

The 1-mm diameter eggs hatch in about 5

days (Swee and McCrimmon 1966) and, in

Illinois, young attain a length of around 13 cm
(5.1 in.) by the late fall of their first year (Smith

1979). Becker (1983) reported the following

total length estimates at each age, based on

scale annuli of individuals captured from the

Wisconsin River: 30.4 cm (12 in.) at 2 years,

40.4 cm (15.9 in.) at 3 years, 49.0 cm (19.3 in.)

at 4 years, 54.3 cm (21 .4 in.) at 5 years, 58.4

cm (23.0 in.) at 6 years, 62.2 cm (24.5 in.) at 7

years, 64.3 cm (25.3 in.) at 8 years, 66.7 cm
(26.3 in.) at 9 years, 69.5 cm (27.4 in.) at 10

years, 74.6 cm (29.4 in.) at 1 1 years, and 76.1

cm (30.0 in.) at 12 years. Sexual maturity

occurs at 3-4 years for males and at 4-5 years

for females (McCrimmon 1968). McCrimmon
also noted that common carp can live for more

than 20 years in North America. Muus and

Dahlstrom (1971) report a life span of up to 40

years. Maximum size is 122 cm (48 in.); adults

commonly exceed 77 cm (30 in.).

Diagnostic Counts

32-38 lateral scales; 17-21 dorsal rays; 5-

6 anal rays; pharyngeal teeth 1,1,3-3,1,1.

Expansion

The distribution and abundance of

common carp in Illinois is not expected to

change in the near future.

Impact on Illinois

Common carp have been present in

Illinois since the earliest surveys, making their

effects on native species difficult to determine.

Common carp tend to destroy vegetation and

increase water turbidity by dislodging plants

and rooting around in the substrate, causing a

deterioration of habitat for species requiring

vegetation and clear water. This species attains

a large size and has become an important

commercial food species in Illinois; however, it

may have done so at the expense of ecologi-

cally similar native species, such as carpsuckers

and buffalos.



March 1996 Non-native Fishes 15

Carassius auratus, goldfish

Figure 5

- —<

/^'$,

*$l«'*»«>* .

1

'

Origin and Range

Native to eastern Asia, the goldfish was

introduced into North America as early as the

late 1600s (Page and Burr 1991) and had

become established in Illinois' rivers by the

time Nelson ( 1 876) conducted his survey of

Illinois fishes. Smith (1979) reported it to be

most abundant in the Illinois River and its

Chicago-area headwaters and sporadically

distributed elsewhere in the state. The goldfish

remains common in Illinois only in the upper

Illinois River system.

Biology

The goldfish prefers vegetated pools, but

its high tolerance of turbidity and pollution has

enabled it to survive in some of the degraded

streams and canals of the Chicago region,

where few other species persist. Trautman

(1957) described the goldfish as similar to the

common carp ecologically, but less tolerant of

cold water, turbidity, siltation, and pollution,

and more dependent on submerged vegetation.

Goldfish usually remain near the bottoms of the

pools or ponds that they inhabit, but occasion-

ally school at the surface. The species is

omnivorous, relying mostly on plants for food

(Robison and Buchanan 1990) but also con-

suming worms and other benthic invertebrates.

Goldfish begin to spawn when the water

temperature reaches about 15.6°C (60°F). The

season lasts from late March to August, and

most activity occurs during the mornings of

sunny days. Each female is accompanied by

two or more males as she broadcasts her

adhesive eggs over aquatic plants and sub-

merged tree roots (Scott and Crossman 1973).

The males follow closely, fertilizing the eggs as

they are released. Webster (1942a) described

females leaping from the water and being

"wildly" chased by males. This species has a

prolonged spawning season with each female

releasing eggs 3-10 times at 8-10 day intervals

(Mansueti and Hardy 1967). Females release

2,000-4,000 eggs at once and the ovaries may

hold from 160,000 to 380,000 eggs (Muus and

Dahlstrom 1971). Berg (1964) and Muus and

Dahlstrom (1971) discuss populations of C.

auratus in Asia and Europe that consist only of

females. The eggs of these goldfish are

stimulated to develop by the sperm of other

carp species, but receive no genetic information

from the sperm. The resulting fry are all

female goldfish.

Mansueti and Hardy (1967) and Battle

(1940) described the development of eggs and

larvae. Eggs hatch 3-10 days after fertilization,

depending on the water temperature (Mansueti

and Hardy 1967). Goldfish total lengths were

reported by Becker (1983) as 12.0 cm (4.8 in.)

at 1 year, 15.1 cm (6.0 in.) at 2 years, and 18.8

cm (7.4 in.) at 3 years. Experimental data

indicate that goldfish produce a substance that

increases the rate of growth in conspecifics

(Lagler et al. 1977), and Swigle (1956) reported

the presence of a secretion that represses

reproduction in overcrowded populations.

Goldfish typically live 6-7 years. Maximum
size is 44.7 cm (17.6 in.); adults commonly

reach 33.0 cm (13.0 in.).

Diagnostic Counts

15-21 dorsal fin rays; 5-7 anal fin rays;

25-31 lateral scales; pharyngeal teeth 0,4-4,0.

Expansion

Goldfish appear to be unable to compete

with native Illinois fishes and became estab-

lished only in severely disturbed areas of

Illinois where native species have disappeared.

The distribution of the goldfish in Illinois will

increase or decrease depending on the future

condition of our streams.



16 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Impact on Illinois

Goldfish have little impact on other

Illinois fishes because they are common only in

areas that are so severely degraded that few

other species are present.

Ctenopharyngodon idella, grass carp

Figure 6

Origin and Range

The grass carp is native to eastern Asia.

It was introduced to North America as a

biological control for aquatic vegetation in the

early 1960s. From its point of introduction in

Arkansas it has now spread or been introduced

to at least 34 states. The first collection in

Illinois was in 1971 (Greenfield 1973) and

Smith (1979) reported its presence in the

Mississippi River as far north as Pike County.

Today grass carp are reproducing in Illinois

(Raibley et al. 1995) and occur sporadically in

the southern half of the Illinois portion of the

Mississippi River, the southern half of the

Illinois River, Lake Michigan and the Chicago

River in Cook County, the Cache River in

Alexander/Pulaski counties, the Big Muddy
River in Jackson County, Clear Creek in

Alexander County, and the Kaskaskia River in

Clinton County.

Biology

Greenfield (1973) and Stanley et al.

(1978) provided reviews of literature and

summaries of most aspects of the life history of

the grass carp. The species inhabits quiet

waters including lakes, ponds, and pools and

backwaters of large rivers. It usually prefers

shallow water but moves into deeper areas as

water temperature decreases (Nixon and Miller

1978). Grass carp can withstand temperatures

from 0° to 35°C (32-95°F) (Stevenson 1965)

and are very tolerant of low oxygen levels and

high salinity.

The grass carp is a voracious feeder

capable of consuming 40% of its body weight

each day (Omarov 1970). While this species is

primarily herbivorous, conflicting reports have

been made on its food preferences. Nikolskii

(1956) reported a diet of rotifers, crustaceans,

and midge larvae until 3.0 cm is reached and

suggested that the grass carp is almost exclu-

sively herbivorous once it reaches that size.

Hickling (1966) also contended that the grass

carp becomes totally herbivorous, despite the

results of his research. He reported data

showing that the gut length to total length ratio

does not change as body size increases, that the

gut is only 2.25 times the length of the fish

(which is much shorter than would be expected

from an exclusively herbivorous fish), and that

only about half of the plant material consumed

is digested. The conclusion that a switch from

omnivory to almost exclusive herbivory was

contradicted by Lin (1935) in a study con-

ducted on a grass carp population in China. In

addition to macrophytes, Lin reported a diet

that included small fishes, earthworms,

silkworm pupae, other insects, and other

nonplant foods. Grass carp have been caught

by hook-and-line fishermen and with trotlines

baited with small fishes (Pflieger 1978).

Stevenson (1965) reported fingerlings feeding

heavily on worms and zooplankton in ponds,

even when algae and commercial food were

available. However, in a different pond study

in which benthic invertebrates and zooplankton

were numerous, grass carp fingerlings fed

almost exclusively on macrophytes (Colle et al.

1978). In a pond containing several other fish

species, grass carp fed primarily on vegetation,

despite the availability of insects (Kilgen and

Smitherman 1971). Tang (1970) suggested that

when macrophyte levels are low or when

competition for other foods is low, the diet

shifts away from macrophytes. The stomach

contents of six large individuals from the

streams of Missouri consisted mostly of

filamentous algae, but also included parts of

terrestrial vascular plants (Pflieger 1978).



March 1996 Non-native Fishes 17

Grass carp migrate upstream towards

spawning grounds as water becomes warmer.

Reported minimum water temperatures

required for spawning range from 15°C (Aliev

1976) to 20°C (Nikolskii 1956). In China,

native populations spawn from April to mid-

August, but activity is heaviest from May to

mid-June (Greenfield 1973). Fecundity can be

very high. Berg (1964) reported a 7-year-old,

7.4 kg (16.3 lb) female that contained 816,000

eggs. Behavior during spawning in natural

populations has not been described. Spawning

generally takes place in large, turbid lowland

rivers. However, in Missouri larvae were

found as far as 8 km (5 mi) upstream from the

mouths of two small streams (41 m [135 ft] and

42.2 m [138 ft] wide) (Brown and Coon 1991).

Brown and Coon felt it unlikely that the larvae

could have swum or been washed this distance

from the Missouri River, suggesting that these

smaller streams might be suitable for grass carp

spawning. Spawning is usually initiated by a

large rise in water level. Spawning may occur

in the absence of a rise in water level. Tem-

perature changes, turbidity changes, and other

environmental factors may be capable of

initiating spawning (Stanley et al. 1978). Grass

carp generally spawn in turbid water, which

probably reduces predation of eggs. Leslie et

al. (1982) reported very high levels of egg

predation in an experiment conducted in a clear

Florida stream.

Grass carp eggs are semipelagic and

require flowing water to prevent sinking and

dying. Varying figures have been reported for

minimum current velocity required for egg

incubation. Several authors report 0.6m/s as

the lowest speed that will allow successful

reproduction in natural populations (Stanley et

al. 1978). A Florida study indicates that

unfertilized eggs may be successfully trans-

ported downstream in as little as 0.23m/s

(Leslie et al. 1982). Incubation time varies

with water temperature and ranges from 60

hours at 17.0°C (62.6°F) to 18 hours at 28.0°C

(82.4°F) (Stanley et al. 1978). Larvae enter

still water soon after hatching and begin to

actively feed after 2-4 days (Vinogradov and

Erokhina 1967). Juveniles prefer quiet water,

usually a lake, reservoir, or stream pool.

Adults and juveniles are known to move long

distances, as evidenced by the short time

between the release of grass carp in Arkansas

and their appearance in large numbers in the

Missouri River (Pflieger 1978). Growth is

rapid in ponds, and grass carp can attain a size

of 8.0 cm (3. 1 in.) and .004 kg (.009 lb) at 6

months, 12.0 cm (4.7 in.) and .021 kg (.046 lb)

at 9 months, 28.0 cm ( 1 1 .0 in.) and .372 kg

(.829 lb) at 12 months, and 50.0 cm (19.7 in.)

and 1.816 kg (4.000 lb) at 18 months

(Stevenson 1965). Eighteen wild-caught

specimens from Missouri averaged 6.9 kg (15.2

lb) at 2-3 years of age, 3.5 kg (7.7 lb) at 3-4

years of age, and 5.4 kg (1 1.9 lb) at 4-5 years

of age (Pflieger 1978). These individuals were

probably hatchery escapees and their unusual

growth pattern is most likely due to varying

conditions under captivity and upon first

entering natural waters. Hickling (1962)

reported age and size at maturity for several

locations: 8-10 years and 2.7-3.8 kg (5.9-8.4 lb)

in Russia, 4 years and 6 kg (13.2 lb) in southern

China, 5-8 years and 8-10 kg (17.6-22.0 lb) in

Israel, and 10-14 months and 2-5 kg (4.4-1 1 lb)

in Malaysia. The grass carp attains a maximum

size of 1.5 m (59 in.) and 32 kg (70.4 lb); adults

commonly reach 76 cm (30 in.).

Diagnostic Counts

34-45 lateral scales; 7-9 dorsal rays; 8-10

anal rays; pharyngeal teeth 2,5-4,2 or 2,4-4,2.

Expansion

The grass carp is known to reproduce in

the Mississippi River drainage (Conner et al.

1980; Brown and Coon 1991), including the

Illinois and Mississippi rivers in Illinois

(Raibley et al. 1995). This species is found

sporadically throughout Illinois and is likely to

become more numerous and widespread,

especially in large rivers.

Impact on Illinois

Although a large species, the feeding

habits of the grass carp make it unsuitable for

sport fishing. Grass carp are commonly caught

by commercial fishermen in the large rivers of



18 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

the southern part of the state. It is not known

how common the grass carp will become and,

thus, its future importance as a source of food

for humans is unknown. Because it feeds on

aquatic plants, the grass carp has the potential

to destroy habitats that are important to many

native species, including threatened and

endangered species. The blacknose shiner

(Notropis heterolepis), pugnose shiner

{Notropis anogenus), Iowa darter (Etheostoma

exile), and other threatened or endangered

species are dependent on aquatic plants for

cover from predators; substrate for prey, such

as aquatic insects; and as spawning substrate.

Other organisms that rely on aquatic plants,

such as waterfowl, also will be negatively

affected by the alteration of vegetated aquatic

habitats by grass carp.

Hypophthalmichthys molotrix, silver carp

Figure 7

Origin and Range

This fish and the similar bighead carp are

native to the large lowland rivers of eastern

Asia. The silver carp was introduced into

Arkansas in 1973 (Henderson 1976). It spread

through the state and by the early 1980s

Arkansas' commercial fishermen were catching

this species from the Mississippi River (Carter

and Beadles 1983). Smith (1979) made no

mention of silver carp in Illinois, but today

commercial fishermen frequently catch the

species in the Mississippi River. Documented

collections exist from Illinois portions of the

Mississippi River drainage in Alexander,

Monroe, and Jackson counties.

Biology

The silver carp is an open-water filter

feeder typically found in large, slow portions of

large rivers. During the winter silver carp

aggregate in large numbers in deep river pools

(Berg 1964). Henderson (1976) discussed diet

and feeding of the silver carp, and much of the

following summary is taken from him. The gill

rakers of the silver carp are fused into a porous

plate allowing particles as small as 4|im to be

filtered from the water. Organisms 40-50|im in

size have been collected from the gut, but

larger items are reduced in size by the pharyn-

geal teeth, which grind food against a cartilagi-

nous plate. The diet consists almost exclu-

sively of plankton, the majority of which is

phytoplankton. Copious quantities are con-

sumed daily with feeding heaviest in the early

morning (Omarov 1970). The gut is long, with

reports of it being slightly longer than 3-5 times

(Henderson 1976) to 12 times the length of the

fish (Nikolskii 1956). Food passes through the

gut quickly, with estimates as low as 4 hours,

indicating that the gut could be filled and

evacuated six times in a 24-hour period

(Omarov 1970). Much of the food passes

through undigested.

No wild spawning of the silver carp has

been described from North America. Robison

and Buchanan (1990) described the spawning

conditions of the silver carp as similar to those

of the bighead carp, which spawns when water

rises after heavy rains (Berry and Low 1970) at

temperatures ranging from 18.3 to 26°C (65.0-

78.8°F) (Chang 1966). Spawning occurs in

large rivers or side channels. The current must

be sufficient to keep the semibuoyant eggs

from sinking and dying. In China, spawning

begins in late May or early June and continues

for 8-10 weeks (Bogaevskii in Berg 1964).

Reproductive ability is reached during the sixth

year of life, and individual fecundity ranges

from 467,000 to 542,000 eggs (Bogaevskii in

Berg 1964). It was previously believed that

neither the bighead nor silver carp could

reproduce in North American rivers; however,

there is now evidence of bighead carp repro-

duction in the Mississippi drainage. Reproduc-

tive requirements are similar for the bighead



March 1996 Non-native Fishes L9

and silver carp, indicating that silver carp may

also have the potential to successfully spawn in

the Mississippi River. However, no evidence

for spawning yet exists.

Eggs of the closely related bighead carp

are about 1.5 mm in diameter when released

and quickly absorb water and swell until the

diameter is about 5 mm (Jennings 1988).

Weights at several year classes were reported

by Bogaevskii (in Berg 1964) as follows: 3.0

kg (6.6 lb) at 5 years, 3.6 kg (7.9 lb) at 6 years,

4.1 kg (9.0 lb) at 7 years, 4.4 kg (9.7 lb) at 8

years, and 4.9 kg (10.8 lb) at 9 years. Faster

growth has been reported, with weights of 1
8-

23 kg (39.6-50.6 lb) reached in 4-5 years

(Henderson 1979). Sexual maturity occurs

during the sixth year of life in Asia, and this

species can live for 20 years. The silver carp

sometimes exceeds 1 m in length and can

exceed 27.3 kg (60 lb), although it does not

commonly exceed 9 kg (20 lb).

Diagnostic Counts

95-103 lateral scales; 12-13 anal rays; 8

dorsal rays; pharyngeal teeth 0,4-4,0.

Expansion

Although not yet known to reproduce in

Illinois, given the recent expansion of its range

the silver carp is likely to become established

in Illinois and occupy large rivers throughout

the state.

Hypophthalmichthys nobilis, bighead carp

Figure 8

Origin and Range

Like the closely related silver carp, the

bighead carp is native to Asia and was intro-

duced into Arkansas in the early 1970s for use

as an aquaculture species (Henderson 1976;

Jennings 1988). It has been collected in

Illinois from the Mississippi River in

Henderson, Hancock, Calhoun, and Madison

counties; the Illinois River in Mason, Schuyler,

and Fulton counties; the Big Muddy River in

Jackson and Union counties; the Cache River

in Alexander County; the Kaskaskia River in

Washington County; and the Kankakee River

in Kankakee County. In addition to these

records, bighead carp have been taken by

fishermen snagging for paddlefish near

Mississippi River Lock and Dam #2 1 and are

commonly captured there by commercial

fishermen (Robert Maher, pers. comm.).

Impact on Illinois

The silver carp has some potential as a

food fish because of its large size, rapid

growth, and acceptable flavor, and it also has

been used in Arkansas for removal of excessive

algae from waste water (Henderson 1977). The

impact of this species on aquatic ecosystems is

not yet known and is highly dependent on the

extent to which its population increases. It has

the potential to do enormous damage to

populations of native organisms because it

feeds on plankton, the same food consumed by

larval fishes and native mussels.

Biology

Jennings (1988) described most aspects

of the life history of this species. Bighead carp

are typically found in quiet waters of large

rivers, lakes, and reservoirs. Larval and

juvenile bighead carp seek out vegetated areas

that have little or no current. The gill rakers of

the bighead carp are enlarged at the distal ends,

forming an almost solid filtering surface

(Henderson 1977). Zooplankton are the major

component of the diet but phytoplankton and

detritus become important when zooplankton

levels are low (Danchenko 1970; Lazareva et

al. 1977). Also, pieces of terrestrial and

aquatic insects have been observed in the gut

of bighead carp (Henderson 1976). This



20 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

species has no real stomach and it can be

inferred that it must feed almost continuously

(Henderson 1976).

Spawning migrations upstream to faster

water are usually triggered by rising water

levels. In China the spawning season usually

lasts from April to June and peaks in May
(Chang 1966). Chang (1966) recorded data for

several years of spawning on the Yangtze River

of China. He found a temperature range of

18.3-23.5°C (65.0-74.3°F), water lever in-

creases of 40-140 cm (15.7-55.1 in.), and water

velocities of 0.78-2.26 m/s (2.6-7.4 ft/s) to be

associated with spawning. The water was very

turbid and spawning took place at the surface.

Dah-Shu (1957) reported spawning below the

surface. Sukhanova (1966) reported a range in

fecundity of 478,000 to 549,000 eggs, but up to

1,100,000 were produced by one individual

(Chang 1966). The eggs are semibuoyant and

require current to keep them from sinking and

dying.

Eggs are about 1.5 mm in diameter when

deposited but they absorb water until the

diameter is about 5 mm (Jennings 1988). Eggs

hatch about 1 day after fertilization in water

temperatures of 22-26°C (72-79°F) (Sukhanova

1966). Shortly after hatching larvae seek out

quiet waters near the shore. Krzywosz et al.

(1977) reported the following estimated

average lengths for each year class for bighead

carp that were raised in ponds for 3 years and

then released into Lake Dgal Wielki in Poland:

12.5 cm (4.9 in.) at 1 year, 24.2 cm (9.5 in.) at

2 years, 39.2 cm (15.4 in.) at 3 years, 50.3 cm
(19.8 in.) at 4 years, 58.0 cm (22.8 in.) at 5

years, 66.7 cm (26.3 in.) at 6 years, and 71.6

cm (28.2 in.) at 7 years. Bighead carp typically

weigh 0.75-1.5 kg (1.65-3.3 lb) at 2 years of

age, and 3-4 kg (6.6-8.8 lb) at 3 years of age.

Maturity has been reported as early as 2 years

and as late as 10 years with males of most

populations reaching maturity a year earlier

than females (Jennings 1988). Bighead carp

have been known to reach a length of 1 .5 m
(4.9 ft) and a weight of 40 kg (88 lb). This

species commonly reaches 75 cm (29.5 in.) and

18 kg (40 lb).

Diagnostic Counts

85-100 lateral scales; 13-14 anal rays; 8-9

dorsal rays; pharyngeal teeth 0,4-4,0.

Expansion

Young-of-the-year have been collected in

Illinois (Burr and Warren 1993), suggesting

that the bighead carp is established in the state.

It is likely to become common in the large

rivers of Illinois.

Impact on Illinois

The bighead carp has a better flavor than

the silver carp and is more likely to be used for

food (Robison and Buchanan 1990). It has

been used for removal of excessive algae and

nutrients from waste water in some areas

(Henderson 1977) and, thus, may offer some

environmental benefits. However, because

bighead carp are planktivorous and attain a

large size, they have the potential to deplete

populations of zooplankton. A reduced

availability of plankton can lead to reductions

in populations of native species that rely on

plankton for food, including all larval fishes,

certain adult fishes (e. g., shad, paddlefish), and

native mussels.

Scardinius erythrophthalmus, rudd

Figure 9

Origin and Range

Native to Eurasia, this minnow was

introduced to the U.S. as early as 1897 (Bean

1897, 1903; Hubbs 1921), but until recently

populations were established only in Maine and

New York (Courtenay et al. 1986). The rudd



March 1996 Non-native Fishes 21

has now been reported in 1 3 other states,

including Illinois, and is being raised in

Oklahoma (Pigg and Pham 1990). Recent

Illinois captures result from the distribution of

the rudd as a bait minnow by the Arkansas fish

farming industry (Burkhead and Williams

1991). The rudd has been found in bait shops

at Carlyle Lake in Clinton County (Brooks

Burr, pers. comm.) This species has been

collected from northern Illinois in Grundy,

Kendall, Lake, and Will counties.

Biology

The rudd is most often found in sluggish,

vegetated waters of lakes and rivers, but is also

known to occur in brackish water. Berg (1964)

reported a population that reproduces in the

saline Aral Sea. It can tolerate very low levels

of dissolved oxygen, but is sensitive to pollu-

tion (Lelek 1987). The rudd is generally found

in upper portions of the water column, where it

is reported by Wheeler (1969) to feed on

surface and terrestrial insects and midwater

crustaceans. He contends that young rudd

consume small amounts of plant material and

that adults are wholly carnivorous. However,

Lelek (1987) reported a larger percentage of

plant matter in the diet of adults, and Muus and

Dahlstrom (1971) described consumption of the

leaves of submerged macrophytes as well as

benthic invertebrates.

In Europe, the rudd spawns from April to

June and usually begins when the water

temperature reaches 18°C (64°F) (Wheeler

1969). The spawning season is often prolonged

and eggs can be laid in two batches. In some

populations gravid females can be found with

their 3-4-week-old fry (Kiselevich 1926).

Breeding males become more brightly colored

than usual and develop tubercles on the head.

During spawning small groups or pairs of rudd

form and the female broadcasts the eggs over

submerged aquatic vegetation. In a river near

the Black Sea fecundity ranged from 96,000 to

232,000 eggs per female (Berg 1964). In

Europe the rudd is known to spawn in associa-

tion with other cyprinid species, often resulting

in hybrid offspring (Muus and Dahlstrom

1 97 1 ). No reproduction has been documented

in Illinois.

Eggs are about 1 .5 mm in diameter upon

release and hatch in 3-14 days depending on

the water temperature. The eggs are very

adhesive and become attached to plants. The

alevins are 4.5 mm upon hatching and remain

attached to vegetation until the yolk sac is

consumed (Wheeler 1969). Berg (1964)

reported growth of rudd from three different

populations. Average standard lengths ranged

from 5.9-6.8 cm (2.3-2.7 in.) at 1 year, 9.5-11.5

cm (3.7-4.5 in.) at 2 years, 12.7-16.3 cm (5.0-

6.4 in.) at 3 years, 17.2-19.5 cm (6.8-7.7 in.) at

4 years, and 21.4-23.0 cm (8.4-9.1 in.) at 5

years. Sexual maturity is usually reached

during the third year of life. This species can

live for more than 10 years. It attains a

maximum length of 48.0 cm (19 in.), and adults

commonly reach a length of 25.0 cm (10 in.).

Diagnostic Counts

36-45 lateral scales; usually 9-11 dorsal

rays; 10-11 anal rays; 10-13 rakers on first gill

arch; pharyngeal teeth 3,5-5,3.

Expansion

This species is being marketed as a bait

minnow and could be found anywhere in the

state. There is no evidence of reproduction in

Illinois, but it seems likely that the species will

become established if it continues to be used as

bait.

Impact on Illinois

If the rudd becomes established in

Illinois, it will compete with native minnows

and thereby alter our aquatic ecosystems.

Although the rudd has been touted as a hardy

bait minnow and as potential forage for

piscivorous sport fishes (Burkhead and

Williams 1991), there is no evidence that the

rudd fulfills these needs better than native

minnows.



22 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Cobitidae

The only cobitid in Illinois is the introduced

Oriental weatherfish.

Misgurnus anguillicaudatus,

Oriental weatherfish

Figure 10

Origin and Range

The Oriental weatherfish is native to Asia

and presumably was released in Illinois waters

by home aquarists. This species was first

collected in Illinois in 1987. Presently the

range of this species in Illinois is Lake Michi-

gan and contiguous streams in Cook County.

Biology

The life history of the Oriental

weatherfish was summarized by Okada (1959-

1960) and much of the following description is

taken from his work. The Oriental weatherfish

inhabits soft-bottomed areas of stream backwa-

ters, swamps, and lakes. It tolerates low

oxygen levels by ingesting air and absorbing

oxygen through a vascularized gut epithelium

as the air passes through the alimentary canal.

The Oriental weatherfish is nocturnal and

usually remains buried in the substrate during

the day. The diet is chiefly mollusks, but

various other benthic invertebrates as well as

occasional plant matter are consumed. Early

free-swimming larvae feed on plant matter.

In its native range the Oriental

weatherfish spawns from April to June. Most

activity occurs in the morning (Okada 1959-

1960). The following description of spawning

is taken from Breder and Rosen (1966). During

spawning the male places his left pelvic fin

above and over the right pelvic fin of the

female and wraps his tail around her. During

the spawn he attaches his mouth to hers. While

the female slowly moves forward, eggs are

released in groups of 20-50. Eggs may be

scattered on the substrate near the bases of

plants or on the plants themselves (Okada

1959-1960). Females may produce as many as

150,000 eggs during a spawn (Sterba 1966).

The reddish eggs of the Oriental

weatherfish are 1.3-1.4 mm in diameter (Okada

1959-1960). Incubation time varies with 1-2

days reported at a temperature of 23-25°C

(73.4-77°F) (Okada 1959-1960) and 8-10 days

reported at a temperature of 21.1 °C (70°F)

(Breder and Rosen 1966). About 25 days after

hatching, the young are fairly well developed

and can be found in the same habitat as the

adults. This species attains a maximum size of

about 30 cm (11.8 in.).

Diagnostic Counts

10 barbels around mouth; 7-8 anal rays; 9

dorsal rays; 6-7 pelvic rays.

Expansion

The Oriental weatherfish reproduces in

Illinois, but it is difficult to predict how

abundant and widespread it will become.

Although it is possible that it will spread

throughout the state, introductions of this

species elsewhere in North America—in

California, Michigan, and Idaho—have resulted

only in localized populations (Page and Burr

1991).

Impact on Illinois

If the Oriental weatherfish remains

confined to extreme northeastern Illinois, it is

unlikely to have much impact on native

species. If it becomes more abundant or

spreads to other areas, it could reduce popula-

tions of native species it preys upon.



March 1996 Non-native Fishes 23

Osmeridae

The only osmerid in Illinois is the introduced

rainbow smelt.

Osmerus mordax, rainbow smelt

Figure 1

1

Origin and Range

The rainbow smelt is native to Arctic and

temperate regions of the northern hemisphere.

Rainbow smelt became established in Lake

Michigan as the result of an introduction in

Crystal Lake, Michigan, in 1912 (Hubbs and

Lagler 1941). When Smith (1979) published

his survey of Illinois, the rainbow smelt was

common in Lake Michigan and occasionally

strayed into the Illinois River system. Today it

remains common in Illinois waters of Lake

Michigan and inhabits the Illinois, Ohio,

Wabash, and Mississippi rivers (Mayden et al.

1987; Burr 1991).

Biology

The rainbow smelt is a schooling marine,

estuarine, and inland species. Marine popula-

tions are seldom found far from shore. In the

Great Lakes rainbow smelt show a seasonal

pattern of movement, probably associated with

spawning activity and temperature changes

(Wells 1968). Young are usually found in

midwater in areas less than 18.3 m (60 ft) deep

(Dryer 1966; Ferguson 1965). In southeastern

Lake Michigan, adults are known to move into

waters of less than 18.3 m (60 ft) but they avoid

the warm water near the shore (Wells 1968).

However, some authors have reported much

deeper summer depths. Wells (1968) reported

rainbow smelt common at 64 m (210 ft) and

sporadic down to 91.4 m (300 ft) in northern

Lake Michigan. Daly and Wiegert (1958)

reported summer depths down to 6 1 m (200 ft),

and Dryer (1966) reported smelt inhabiting

water of 36.6-89.6 m (120-294 ft) during the

summer in Lake Superior.

Marine populations of rainbow smelt feed

primarily on shrimp, annelid worms, and young

fishes (Bigelow and Schroeder 1953). In the

Great Lakes, most studies indicate that the

opossum shrimp (Mysis relicta) is the most

important component of the diet (Schneberger

1936; Baldwin 1950; O'Gorman 1979; Scott

and Crossman 1973) although piscivory has

also been noted, with alewives (O'Gorman

1979), minnows (Creaser 1925; Gordon 1961),

sculpins (Schneberger 1936), and smelt

(Schneberger 1936) making important contri-

butions to the diet. In Lake Erie the volume of

fish in the diet ranged from 5.3% in the spring

to 95.7% during the fall (Price 1963). It was

hypothesized that the low utilization of fish in

the spring was due to the abundance of inverte-

brate prey. Price also found that fishes were

taken only by smelt greater than 12.7 cm (5.0

in.) in length. Food in Crystal Lake during the

summer consisted almost exclusively of

emerald shiners (Notropis atherinoides)

(Creaser 1925). Mayflies are important

seasonally (Baldwin 1950; Gordon 1961).

In the fall and winter of 1942-1943, a

massive die-off of smelt occurred in Lakes

Michigan and Huron (Van Oosten 1947). The

cause was a communicable viral or bacterial

pathogen. Populations recovered to their

former abundance after about 5 years. The

rainbow smelt is tolerant of suspended sedi-

ments (Chaisson 1993) and is known to contain

antifreeze proteins that lower the freezing point

of the serum (Ewart and Fletcher 1989). In

some eastern lakes the rainbow smelt is heavily

preyed on by Atlantic salmon, composing more

than 95% of its winter diet by volume (Sayers

etal. 1989).

Spawning occurs in the spring for about 2

weeks, during which adults congregate and

broadcast their adhesive eggs over the substrate

(Smith 1979). Spawning begins at a water

temperature of about 4.4°C (40°F) (Daly and

Wiegert 1958). The following description of

the spawning behavior of rainbow smelt in



24 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Crystal Lake, Michigan, is a summary of

Creaser (1925). In early April the smelt began

to run up Cold Creek while there was still ice

on much of the lake. The portion of the river

used for spawning was clear, fast, not more

than 76 cm (30 in.) deep, and ran over gravel

and sand. Most of the spawning smelt entered

the stream at dusk and returned to the lake as

dawn approached, although some remained in

the creek in dark places under a bridge or

projecting shelves of ice. Many gulls gathered

to feed upon the smelt. The upstream migra-

tion was short with few smelt moving more

than 120 m (400 ft) upstream. So many smelt

tried to enter the stream that the bottom could

not be seen and many were unable to enter.

Those that were unable to enter the stream

spawned over the gravel-bottomed mouth of

the creek. Smelt ate little while spawning.

The males and females became covered with

breeding tubercles and were sometimes

observed vibrating against each other. The

smelt were tightly packed together in the

stream and released eggs at random. The day

after a spawning run, eggs could be collected

up and down the length of the stream.

A Lake Huron study indicated that runs

are heaviest in streams with rapid current at the

mouth (Baldwin 1950). Langois (1935)

provided a second description of the spawning

run in Cold Creek that was similar to that of

Creaser (1925) in all respects except the

positions of the males and females during the

release of eggs and milt. He described a female

swaying in the current with five attendant

males, each holding a position slightly down-

stream of the female. The female released

clusters of eggs as she swayed in the current

and these drifted downstream where they were

presumably fertilized by the males. Hoover

(1936) studied an inland population in New
Hampshire. He reported that the male assumes

a position anterior and dorsal to the female and

violently drives her to the bottom or toward

shore. Males attended females in ratios similar

to the sex ratio in the stream. No more than 50

of the strongly adhesive eggs were ever

released at once. Bailey (1964) found that

males outnumber females on the spawning area

at the beginning of the run, but that females

outnumber males towards the end of the run.

Rainbow smelt normally spawn in

streams but they also spawn on the shores of

lakes (Lievense 1954; Rupp 1959). Rupp

(1965) reported that smelt gather in shallow

water near shore as night approaches and form

a tight school. Eggs were released seemingly

with little attention to substrate type. Many of

the eggs were destroyed by the action of waves

and changes in the level of the lake. Rainbow

smelt spawn from age 2 to age 5 (Creaser

1925). In Lake Superior, average fecundity for

fishes ranging from 18.5 to 23.4 cm in size

(7.3-8.8 in.) was 31,338 eggs (Bailey 1964).

McKenzie (1964) reported a range of 8,500

eggs from a 12.7 cm (5.0 in.) smelt to 69,600

from a 20.9 cm (8.2 in.) individual. Grout

(1983) reported the collection of two hermaph-

roditic individuals, but he was unable to

determine whether they were capable of

reproduction.

Eggs average 0.9 mm in diameter.

Hatching occurs in 8 days at a temperature of

15°C (59°F) (Cooper 1978) and in about 29

days at 6-7°C (42.8-44.6°F) (McKenzie 1964).

Females grow faster than males and have an

increasingly larger average size than males

after 2 years of age (Bailey 1964). Growth in

Green Bay, Wisconsin, was reported by

Schneberger (1936) with the following average

lengths at each year: 17.8 cm (7.0 in.) at 2

years, 25.4 cm (10.0 in.) at 3 years, 30.5 cm
(12.0 in.) at 4 years, and 35.6 cm (14.0 in.) at 5

years of age. Females also live longer than

males based on their dominance of the 5- and

6-year-old age classes (Bailey 1964). Bailey

(1964) found that in Lake Superior 40.7% of 2-

year-old males were sexually mature but that

only 17.7% of the females were mature at 2

years. All individuals of both sexes were

mature at 3 years. Males reached maturity at a

shorter average length, but the smallest mature

individual was 12.7-13.2 cm (5.0-5.2 in.) for

both sexes (Bailey 1964). Maximum adult size

is 33 cm (13 in.); adults commonly reach 20 cm
(8 in.).

Diagnostic Counts

62-72 lateral scales; 11-16 anal rays;

usually 28-32 rakers on first gill arch.



March 1996 Non-native Fishes 25

Expansion

Rainbow smelt reproduce in Lake

Michigan and will probably remain common
there. In winter samples from the Mississippi

River the rainbow smelt is sometimes the most

abundant species (Brooks Burr, pers. comm.).

However, it has not been collected in late

summer and probably does not reproduce in the

Illinois portion of the river. Rainbow smelt are

expected to be only sporadically encountered in

the large rivers of Illinois.

Impact on Illinois

In Lake Michigan the rainbow smelt may

have played a role in the declines of some of

the native whitefishes. Anderson and Smith

(1971) attributed the decline of the lake herring

(Coregonus artedii) to competition from the

rainbow smelt at the larval stage. If the rainbow

smelt becomes common in Illinois rivers, it will

compete with native species for food and prey

on small fishes. It may serve as food for large

fishes. The rainbow smelt is not harvested

commercially in Illinois but is favored by many

recreational fishermen (Becker 1983).

Salmonidae

Key to trouts and salmons

1. Mouth of adult white inside; usually 10-12

branchiostegal rays 2

Mouth of adult black inside; usually 12-19

branchiostegal rays 6

2. Black or brown spots on light body; fewer

than 1 60 lateral scales 3

Light spots (occasionally red) on dark body;

more than 160 lateral scales 5

3. Usually 9 anal rays; adults with x-shaped

spots on side; vomerine teeth little

developed, those on the shaft of the bone

few and deciduous (Atlantic salmon) ....

Salmo salar

Usually 10-13 anal rays; side usually with

round spots; vomerine teeth well devel-

oped, those on the shaft of the bone

numerous, persistent, and arranged in 1

zigzag or 2 alternating rows 4

4. Few large black or brown spots on body,

few or none on caudal fin; reddish

spots more or less strongly developed

(often surrounded by light border);

adipose fin orange or red-orange, without

dark margin or spots; no pink to rose

stripe along side of body (brown trout) . .

Salmo trutta

Many small black or brown spots on body

and caudal fin; no red spots; adipose fin

olive, with black margin or spots; broad

pink to rose stripe along side of body

(rainbow trout) . . Oncorhynchus mykiss

5. Caudal fin little forked; red spots on body;

lower fins each with black stripe near

leading edge; 9-12 gill rakers; mandibular

pores usually 7-8 on each side (brook

trout) Salvelinus fontinalis

Caudal fin strongly forked; no red spots on

body; lower fins without black stripe; 12-

14 gill rakers; mandibular pores usually 9

or 10 on each side (lake trout)

Salvelinus namaycush

6. 147-205 lateral scales; large black spots on

back and both lobes of caudal fin, largest

as large as eye; 24-35 rakers on first gill

arch; breeding male with distinct hump-

back (pink salmon)

Oncorhynchus gorbuscha

112-165 lateral scales; small dark spots on

back and caudal fin, largest as large as

pupil of eye; 16-26 rakers on first gill

arch; breeding males without humpback

7

7. Entire mouth, including gums, black; 14-19

anal rays; 140-185 pyloric caeca; small

black spots on both lobes of caudal

fin (chinook salmon )

Oncorhynchus tshawytscha

Gums whitish; 11-15 anal rays; 45-1 14

pyloric caeca; small black spots, when

present on caudal fin, on upper fin only

(coho salmon) . . Oncorhynchus kisutch



26 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Salmo salar, Atlantic salmon

Figure 12

Origin and Range

Atlantic salmon are native to the north-

eastern coastal drainages of North America,

Lake Ontario, and Atlantic coastal areas of

Europe. Many natural landlocked populations

occurred in Europe and eastern North America,

including one in Lake Ontario. Unfortunately,

Atlantic salmon were extirpated from Lake

Ontario before 1900 and repeated efforts to re-

establish the species in the lake have failed.

Presently, natural and introduced landlocked

populations exist in several lakes in eastern

Canada and the northeastern U.S. Atlantic

salmon have been widely stocked outside their

native range but have rarely become estab-

lished. In Illinois they have been found only in

the lower Mississippi River (Burr 1991).

Biology

Most of the following information on the

biology of the Atlantic salmon is taken from

Scott and Crossman (1973) and Smith (1985).

Atlantic salmon are typically anadromous and

spawn in gravel-bottomed streams. They

migrate up streams in the spring and summer,

but do not spawn until October or November.

Members of landlocked lake populations move

into streams during early fall. A female

constructs a nest by turning sideways and

beating her caudal fin to fan out a depression

(redd) in the substrate. While the female

constructs the redd, a male defends the female

and nest from other males. When the female is

ready to spawn she positions herself in the

bottom of the redd, the male moves next to her,

and eggs and milt are released. The female

then begins a new redd immediately upstream

of the old one, covering the fertilized eggs with

newly displaced gravel. This process is

repeated until the female has deposited all of

her eggs. Females deposit about 700 eggs/

pound of body weight. Adults often survive

spawning and return to the ocean or lake.

Atlantic salmon may spawn more than once.

Atlantic salmon eggs range from 5 to 7

mm in diameter and hatch in about 1 10 days

depending on the water temperature. After

hatching the young remain buried in the gravel

until the yolk sac is absorbed, usually in May
or June. Growth in the stream is slow, and

after 2-3 years the young are 13-15 cm (5-6

in.). At this time the young move downstream

to the ocean or lake, where they usually spend

1-2 years before spawning. Atlantic salmon

generally do not live longer than 9 years,

although some populations are believed to

have a slightly longer life span. Adult Atlantic

salmon feed on fish and crustaceans in the sea,

but they do not feed during spawning runs.

Young rely mostly on aquatic insects, with

terrestrial insects playing a smaller role in the

diet. Anadromous Atlantic salmon are typi-

cally larger than those in lake populations, with

adults averaging around 4.5 kg (10 lb) and 1.4

kg (3 lb), respectively. The maximum length is

140 cm (55 in.); adults commonly reach 61 cm
(24 in.).

Diagnostic Counts

Usually 12 branchiostegal rays; 11 dorsal

rays; 109-121 lateral scales; 8-11 anal rays;

young have 8-11 narrow parr marks.

Expansion

This species is not reproducing in Illinois

and is not likely to become established.

Impact on Illinois

This species is too rare in Illinois to have

an ecological impact.



March 1996 Non-native Fishes 27

Salmo trutta, brown trout

Figure 13

Origin and Range

The brown trout is native to Europe,

western Asia, and northern Africa. It has been

stocked heavily throughout the world, includ-

ing Lake Michigan and northern Illinois.

Reproduction may have occurred in Piscasaw

Creek in the northern part of the state.

Biology

The extensive literature on this species

was summarized by Carlander (1969), Becker

(1983), Moyle (1976), and Scott and Crossman

(1973). Much of the following information is

taken from them. Brown trout are best suited

to cool, medium to large rivers with a gravel or

rocky substrate; however, they are more

tolerant of high temperatures and turbidity than

are other trout species. Brown trout can

tolerate temperatures as high as 26°C (78°F)

for short periods of time, but optimal tempera-

tures range from 7-19°C (45-66°F). In the

Great Lakes, brown trout are usually found

near shore in water less than 15 m (49 ft) deep.

The diet of young brown trout consists mostly

of aquatic invertebrates during the winter and

terrestrial invertebrates and worms during the

summer. Larger individuals become increas-

ingly piscivorous with increased size; fishes

compose about 70% of the diet in the largest

individuals.

Most populations of brown trout spawn

between October and December in water from

2 to 13°C (35-55°F). Spawning usually takes

place in fast, gravel-bottomed streams. The

female uses her caudal fin to construct a nest in

the substrate, which is guarded by one male.

When the female is ready to spawn she enters

the nest, the male moves alongside her, and

gametes are released. After the spawn the

female immediately begins to beat her caudal

fin above the gravel just upstream of the nest to

simultaneously cover the fertilized eggs and

begin construction of a new nest. This process

is repeated many times until the female has

released all of her eggs, usually from 400 to

21,000. Brown trout do not die after spawning

and can spawn for several years. In the Great

Lakes, spawning can occur on rocky areas near

shore as documented by Eddy and Underhill

(1974) in Lake Superior and by Daly (1968) in

Lake Michigan.

The amber-colored eggs are 4-5 mm in

diameter and hatch in 48 days at 1.9°C (35°F)

and in 33-36 days at 1 1 . 1 - 1 1 .2°C (52°F) (Aver

1982). Fry begin feeding 3-6 weeks after

hatching. Growth is usually rapid. In southern

Wisconsin, brown trout are known to attain a

length of 30.5 cm (12 in.) and sexual maturity

at an age of 20 months. While males in some

populations are mature before 2 years of age,

maturity usually occurs after the second or third

year. In Lake Michigan, brown trout released

at 20 cm (8 in.) and 1 year of age reached 44.5

cm (17.5 in.) at 2 years of age and 54.6 cm
(21.5 in.) after their second growing season in

the lake (Daly 1968). Maximum size is 103 cm
(40.5 in.); adults commonly reach 38 cm (15

in.).

Diagnostic Counts

Usually 10 branchiostegal rays; 9 dorsal

rays; 120-130 lateral scales; 10-12 anal rays;

young have 9-14 short narrow parr marks.

Expansion

Brown trout are highly valued as game

fish and have at times been heavily stocked in

Illinois; however, there is little suitable habitat

and the species does not reproduce.

Impact on Illinois

Brown trout are insufficiently common in

Illinois to affect other species. Neither the

brown trout nor any of the other introduced

salmonids are being commercially harvested in

Illinois, but a considerable sport fishery has

developed for them.



28 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Oncorhynchus mykiss, rainbow trout

Figure 14

Origin and Range

Rainbow trout are native to the western

coast of North America and have been widely

introduced throughout the world. This anadro-

mous species has been stocked repeatedly in

Lake Michigan and several northern Illinois

streams. Rainbow trout also have been stocked

in some central and southern Illinois reservoirs

and are known to have reproduced in Devil's

Kitchen Lake, a reservoir in Williamson

County (Brooks Burr, pers. comm.).

Biology

Scott and Crossman (1973) and Moyle

(1976) described the life history of this species

in detail, and most of the following information

is taken from them. Rainbow trout usually are

found in streams with cool, clear water and a

rocky substrate. Lakes and reservoirs that are

deep enough to remain cool on the bottom

throughout the summer also provide suitable

habitat. In streams, feeding territories are

established, and food consists mostly of drift

organisms in the summer and benthic inverte-

brates during winter. However, in lakes and

reservoirs, feeding territories have not been

observed, and diet consists mostly of benthic

invertebrates with fishes being increasingly

important in the diet of large individuals.

Feeding is heaviest around dusk. In Lake

Taneycomo in Missouri, 90% of the diet

consisted of amphipods (Pflieger 1975).

Optimum temperature range is 13-21°C (55-

70°F).

Rainbow trout usually spawn in the

spring, most commonly between April and

June. However, in the Great Lakes, spawning

is known to begin as early as December, and at

high altitudes in western regions it may take

place as late as August. Spawning occurs over

gravel riffles in which a female constructs a

nest by beating her caudal fin above the

substrate to dig a nest (redd). Males compete

for females, and a male defends a female and

her nest from intrusion by other males. During

the spawn the female enters the nest and

remains in the center while one or two males

assume parallel positions and press against her

as gametes are released. The female then

enlarges the nest on the upstream side, covering

the eggs with gravel. Individual females dig

and spawn in several nests, often with the same

male. Each female may deposit from 200 to

12,000 eggs. Unlike the Pacific salmon

species, rainbow trout do not die after spawn-

ing and may spawn during subsequent years.

During spawning, the temperature is usually

10-15°C (50-60°F). .There is little evidence

that successful reproduction occurs in areas

other than rocky streams.

Eggs are 3-5 mm in diameter and usually

hatch in 4-7 days. Fry commence feeding in

approximately 15 days. Progeny of lake

residents may immediately return to the lake,

but have been known to spend up to 3 years in

the stream. Growth is most rapid in reservoirs

and lakes but varies considerably depending on

habitat conditions and on the origin of the

population in question. Males can be sexually

mature as small as 13 cm (5 in.) and at 1 year

of age. However, both sexes usually reach

sexual maturity after 3-5 years. Life expect-

ancy of Great Lakes rainbow trout seems to be

6-8 years. Rainbow trout reach a maximum of

1 14 cm (45 in.) in length; adults commonly

reach 38 cm (15 in.).

Diagnostic Counts

115-130 lateral scales; 10-12 dorsal rays;

8-12 anal rays; young have 5-10 widely spaced,

short oval parr marks.

Expansion

Rainbow trout are established in upper

Lake Michigan and sometimes stray into

Illinois waters. However, little suitable habitat



March 1996 Non-native Fishes 29

for this species exists in Illinois, and the

rainbow trout is not expected to become

established.

Impact on Illinois

The rainbow trout is popular as a sport

fish wherever it is stocked in Illinois. It rarely

reproduces in the state and does not become

common enough in Illinois streams to have a

serious effect on native species.

Oncorhynchus gorbuscha, pink salmon

Figure 15

Origin and Range

The pink salmon is native to the north-

western coast of North America and the

northeastern coast of Asia, including Japan and

Korea. Pink salmon now found in the Great

Lakes result from a 1956 stocking of about

20,000 surplus fingerlings into the Current

River, a tributary to Lake Superior (Parsons

1973). The eggs were brought from the Skeena

River, British Columbia, and raised in the Port

Arthur Fish Hatchery on Thunder Bay, Ontario,

in an attempt to establish spawning runs in the

Hudson Bay drainage (Schumacher and Eddy

1960). By 1969, pink salmon had spread

through most of Lake Superior and had been

found in Lake Huron (Parsons 1973). By 1975

the species had spread through northern Lake

Huron and northern Lake Michigan (Wagner

1976). Pink salmon have not been stocked in

Illinois, but strays from northern Lake Michi-

gan are sometimes collected in the Illinois

portion of the lake.

Biology

A detailed account of pink salmon life

history was given by Heard (1991), and most of

the following information is taken from him

and Scott and Crossman (1973). In the Great

Lakes pink salmon are usually found in open

water near the surface (Becker 1983). Pink

salmon seldom feed in streams either as adults

or as newly hatched fry. Adults feed mostly on

pelagic macrocrustaceans, with fish playing

increasingly important roles as they increase in

size. Opossum shrimp, amphipods, and

copepods are important dietary components in

the Great Lakes. Fry and adults feed and

migrate in schools.

In native North American populations,

migration to streams and estuaries occurs from

July to September, although it begins in June in

some Asian populations (Takagi et al. 1981).

Spawning begins at a temperature of about

10°C (50°F) and peaks at 16°C (61°F) . The

distance of the upstream migration is generally

smaller for the pink salmon than for other

Pacific salmon species, often no more than 64

km (40 mi). Spawning sometimes occurs in the

intertidal areas of small rivers. Prior to

spawning, male pink salmon develop a large

hump on the back and the mouth becomes a

strongly hooked kype. Both sexes undergo

atrophy of the alimentary canal and digestive

organs, thickening of the skin, and color

changes. These changes take 4-6 weeks, during

which the fish remain in deeper pools of

streams or in estuaries before migrating

upstream. Spawning beds are usually gravel

riffles. The female constructs a redd by beating

her tail above the gravel in the manner of other

salmon and trout. When the female is ready to

spawn she enters the nest and is joined by one

or several males, and gametes are released.

Males often spawn with more than one female.

Eggs are covered by further nest construction

upstream of the fertilized eggs. Females carry

1,200-1,900 eggs. Adults usually die shortly

after spawning is completed; however, the

female guards the eggs from other females as

long as she lives.

Eggs are about 6 mm in diameter and

hatch from December to February, depending

on the water temperature. The fry remain

under the gravel until the yolk sac is absorbed,

usually in April or early May. Pink salmon fry



30 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

migrate to estuaries immediately upon absorp-

tion of the yolk sac. They usually do not feed

in fresh water, but remain in an estuary to feed

for several months before migrating to the open

sea. Pink salmon generally live for 2 years, but

adults at 3 years of age have been reported.

Since this 2-year life cycle is fixed, odd-year

and even-year spawning populations in the

same stream are reproductively isolated and are

usually distinguishable genetically. Some
streams have spawning runs only every other

year.

The Great Lakes population of pink

salmon is the only one known to complete its

life history entirely in fresh water and shows

more variation than its anadromous counter-

parts. While most aspects of biology are very

similar to those displayed by anadromous

populations, Great Lakes individuals show

lower fecundity, smaller adult size, and more

variable age at maturity, presumably related to

less favorable growing conditions. The

originally established population in Lake

Superior spawned only during odd years, but

later an even-year population developed from

age-3, odd-year spawners. Pink salmon have a

smaller adult size than other Pacific salmon

species with a maximum of 76 cm (30 in.);

adults commonly reach 51 cm (20 in.).

Diagnostic Counts

169-198 lateral scales; 10-16 dorsal rays;

13-19 anal rays; young lack parr marks.

Expansion

This species is present in Illinois only as

stragglers from northern Lake Michigan and is

not expected to reproduce in Illinois nor to

invade new areas.

Impact on Illinois

The pink salmon is too rare in Illinois to

have an important impact on other species.

Oncorhynchus tshawytscha, chinook salmon

Figure 16

Origin and Range

The chinook salmon is native to the

northwestern coast of North America and the

northeastern coast of Asia. It was introduced

into Lake Michigan in 1967 by the Michigan

Department of Conservation (Smith 1979).

Today the chinook salmon is fairly common in

Lake Michigan but must be continuously

stocked to maintain a population.

Biology

Healey (1991) discussed the biology of

the chinook salmon in detail and the following

information is taken from his work and that of

Scott and Crossman (1973). Newly emerged

chinook fry are usually associated with the

stream edge and woody cover, but as they

increase in size they move to areas with a

higher water velocity. Those that remain in the

natal stream feed mostly on terrestrial inverte-

brates at the surface, but benthic and midwater

feeding also occur. When fry first emerge from

the gravel they feed in schools, but those that

remain in the stream soon establish feeding

territories. Large chinook young do not

become piscivorous in streams as the young of

coho salmon do. Those young that migrate

downstream to the estuary or lake feed mostly

on midges and other insects. Fishes make up

about 97% of the diet of adults at sea, with

squid and other invertebrates making up the

other 3%. Optimal temperature range for fry is

12-14°C (53.6-57.2°F) and they cannot tolerate

temperatures higher than 25.PC (77.2°F)

(Brett 1952).

Chinook salmon spawning may take

place at almost any time of the year, and many



March 1996 Non-native Fishes 31

streams have more than one run each year.

However, in most rivers spawning activity

occurs from late summer to late fall. Spawning

may take place anywhere from just upstream of

tidal influence to as far as 3,200 km (2,000 mi)

upstream (Major et al. 1978). Spawning beds

can be found in small shallow creeks (Vronskiy

1972) as well as main channels of large rivers

(Chapman 1943; Hallock et al. 1957). Spawn-

ing usually occurs in much larger rivers than

those used by other Pacific salmon. The depth

at which the spawning bed is found also varies

considerably, ranging from a minimum of 5 cm
(2 in.) to an estimated maximum of 7 m (23 ft).

As with other salmon, the female constructs the

redd. A dominant male usually defends each

female and redd, and satellite males often are

present. During spawning the female and

dominant male enter the nest, and eggs and

sperm are released. Satellite males frequently

dash into the nest and release gametes. The

female deposits the eggs in clumps during

spawning, and each clump is buried in a pit and

covered with gravel displaced by the construc-

tion of the next spawning pit. A female usually

deposits 4 or 5 egg clumps during the spawn.

The total number of eggs deposited by a female

ranges from 2,000 to 17,000. Females remain

to defend the redd after spawning and may do

so for as long as 25 days, although death may
occur as soon as 4 days after the start of

spawning activity. Members of Great Lakes

populations sometimes spawn on shoals within

the lake instead of ascending a stream.

The eggs of chinook salmon are 6-7 mm
in diameter and incubate for 30-150 days,

largely dependent on water temperature.

Above 17°C (63°F), young suffer retarded

growth and increased mortality (Davidson and

Hutchinson 1938). The fry spend 2-3 weeks in

the gravel until the yolk sac is absorbed. They

may proceed to the estuary after only a few

weeks in the natal stream, although many
remain for up to 2 years. In anadromous

populations most adults spend 2-3 years at sea,

although spawning adults up to 9 years of age

have been reported. Stocked chinook salmon

in Lake Michigan have a 4-year life span

(Becker 1983). Chinook salmon are the largest

of the introduced salmon species and growth in

Lake Michigan is rapid. Daly (1971) reported

average lengths for each year class: 25.4 cm
(10 in.) at 1 year; 63.5 cm (25 in.) at 2 years;

86.4 cm (34 in.) at 3 years; 102 cm (40 in.) at 4

years. The largest reported chinook salmon

was a 147 cm (58 in.), 57.2 kg (126 lb)

individual captured in Alaska; adults often

reach 91 cm (36 in.).

Diagnostic Counts

130-165 lateral scales; 10-14 dorsal rays;

14-19 anal rays; young have 6-12 large pan-

marks.

Expansion

The chinook salmon does not reproduce

in Illinois but does reproduce in the tributaries

of northern Lake Michigan where it is more

common. Chinook salmon are not expected to

be found in Illinois outside Lake Michigan.

Impact on Illinois

The chinook salmon aids in the control of

the introduced alewife and is a popular sport

fish. Like other introduced Pacific salmonids,

the chinook salmon has the potential to

compete with the lake trout and other native

species.

Oncorhynchus kisutch, coho salmon

Figure 17

Origin and Range

Coho salmon are native to the western

coast of North America and the northeastern

coast of Asia. This species was first introduced

to Lake Michigan in 1967 as a sport fish and to

control the alewife population. It is not found

in Illinois outside Lake Michigan.



32 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Biology

The following account is based on the

work of Moyle (1976) and Scott and Crossman

(1973), and the comprehensive review of the

species by Sandercock (1991). Freshwater

habitat for young coho salmon consists of

medium-sized pools and quiet stream margins

where feeding territories are established. The

territory size increases with fish size and the

number of suitable territories in a stream limits

the abundance of coho. Young coho salmon

are visual predators feeding mostly in the water

column and at the surface, and are reported to

jump from the water to capture low-flying

insects. Insects are the principal component of

the diet until about 1 year of age, at which time

fishes become increasingly important. Fry of

other salmon species often are consumed.

Marine invertebrates are the most common
food items when coho salmon first leave the

streams, but adult coho become more piscivo-

rous until fishes are about 80% of the diet.

In most populations, spawning takes

place from November to January, but occurs

from early September to early October in the

Great Lakes. Water temperature is usually 7.2-

15.6°C (45-60°F) during spawning migrations

(Reiser and Bjornn 1979). Coho salmon

migrate further upstream than pink salmon, but

not as far as chinook salmon. Coho usually do

not migrate more than 238 km (150 mi)

upstream (Godfrey 1965), but a known

spawning area in Alaska is 1,830 km (1,152

mi) from the Pacific Ocean (McPhail and

Lindsey 1970). Coho salmon usually spawn in

small streams that often have a width of 1 m or

less. While small streams with a gravel bottom

are preferred, coho salmon are the most tolerant

of variable spawning conditions and sometimes

spawn over sand or silt and in a wide variety of

stream sizes. Prior to spawning, male coho

salmon develop enlarged jaws and teeth, often

to the extent that the mouth can no longer be

closed. The jaws of females also become

enlarged but to a lesser extent than those of

males. When the spawning grounds are

reached, the female selects a nest site, which

she defends from other females. The female

constructs the nest (redd) by beating her tail

above the substrate to lift gravel and silt into

the water column, where it is carried down-

stream. Several males can be in attendance, but

usually a dominant male will attempt to drive

others away. When the female is ready to

spawn, she enters the nest and inserts her anal

fin into the substrate. The dominant male

assumes a parallel position and gametes are

released. Satellite males often rush in and

deposit sperm. As in other salmon species,

after spawning the female immediately begins

construction of a new nest upstream of the old

one, thereby covering the fertilized eggs with

gravel. Females produce 2,000-5,000 eggs.

Males continue to exhibit courting behavior

until they are too weak to maintain a position in

the current. Females may guard the fertilized

eggs until death, but sometimes the post-spawn

female will continue digging motions even

though the new nests are shallow and nonfunc-

tional. Males and females usually die within 2

weeks of spawning.

Eggs of Pacific populations range from

4.5-6.0 mm in diameter, but in Lake Ontario

they range from 6.6 to 7.1 mm. Hatching

occurs anywhere from 35 to 115 days after

fertilization, depending on the temperature.

After hatching, fry remain in the gravel until

the yolk sac is gone, usually 2-3 weeks. Upon

leaving the redd, they feed in schools for a

short time before establishing feeding territo-

ries. Coho young remain in the stream for 1-2

years, after which they migrate to the lake or

ocean. Most smolts (juvenile salmon) are

about 10 cm (4 in.) when they migrate to open

water. Usually about 1 8 months are spent in

the lake or ocean, although some males return

after only one season. Spawning migration to

streams other than the natal stream is more

common in the Great Lakes than in anadro-

mous populations, where about 85% of the

individuals return to their natal streams.

Maximum size is 98 cm (38.5 in.); adults

commonly reach 53 cm (21 in.).

Diagnostic Counts

121-148 lateral scales; 9-12 dorsal rays;

12-17 anal rays; young have 8-10 narrow parr

marks.



March 1996 Non-native Fishes 33

Expansion

Coho salmon are established in Michi-

gan waters of Lake Michigan. No reproduction

occurs in Illinois, but strays from northern parts

of the lake are found in Illinois. Coho salmon

are by far the most common introduced

salmonid in Lake Michigan (Tom Trudeau,

pers. comm.). They are not expected to be

encountered in Illinois streams.

Impact on Illinois

Like the chinook salmon, the coho

salmon aids in the control of the introduced

alewife and is a popular sport fish. It also has

the potential to compete with the lake trout and

other native species.

Atherinidae

Key to silversides

1. Long beaklike snout (1.5 times eye diam-

eter); first dorsal fin origin above anal fin

origin; 74-87 lateral scales; 22-25 anal

rays (brook silverside)

Labidesthes sicculus

No beaklike snout (snout length equal to eye

diameter); first dorsal fin origin in front

of anal fin origin; 36-44 lateral scales;

usually 16-18 anal rays (inland silverside)

Menidia beryllina

Menidia beryllina, inland silverside

Figure 18

Origin and Range

Primarily a marine and brackish water

species native to the Atlantic and Gulf coasts of

the U. S. and the lower Mississippi River, the

inland silverside has been widely introduced as

a forage species for game fish. Smith (1979)

mentioned only that this species had been

captured in Illinois. The inland silverside has

been stocked in Lake Baldwin, Randolph/St.

Clair counties; Lake of Egypt, Jackson/

Williamson counties; and Rend Lake, Franklin/

Jefferson counties. Collections from Illinois

waters include those from the Cache River,

Wabash River, lower Mississippi and Ohio

rivers, and from the Kankakee River system in

Will County.

Biology

The inland silverside is usually found in

large schools near the surface of sand-bot-

tomed, clear, quiet waters. It is often found in

shallow water during the day but retreats to

deeper water at night (Hubbs 1982). It is a

visual feeder and has been reported to feed

most heavily shortly after sunrise (Elston and

Bachen 1976); however, Hubbs (1982)

reported more nighttime feeding. In a Califor-

nia study, the diet consisted mostly of zoop-

lankton with Ceriodaphnia sp., Daphnia pulex,

and emerging dipterans the most important

items (Elston and Bachen 1976). During the

winter and while spawning, little foraging

occurs and growth is greatly reduced (Hubbs

1982).

Most of what is known about the

spawning of the inland silverside in fresh water

results from studies on Lake Texoma, which

have been summarized by Hubbs (1982).

Inland silversides begin to spawn in March or

early April and continue until the water

becomes too warm (about 30°C [86°F]),

usually in late June or July (Hubbs and Bailey

1977). Females produce clutches daily

throughout the breeding season, each with a

weight of about 7.5% that of the female (Hubbs

1976). Clutch size varies in Lake Texoma from

384 to 1,699 eggs, depending on the size of the

female (Mense 1967).

Incubation time is 15 days at 18°C

(64.4°F) but can be less than 5 days when the

water is wanner (Hubbs et al. 1971). Upon
hatching, young inland silversides are about 0.5

cm (0.2 in.) in length. Young can grow to a

maximum of 7.0 cm (2.8 in.) by the end of the



34 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

breeding season in late July (Hubbs and Dean

1979). Growth of young-of-the-year is density

dependent and is fastest after years with a high

winter mortality (Hubbs and Dean 1979).

Females are known to become reproductive at

sizes as small as 4.8 cm (1.9 in.), and young-of-

the-year sometimes reproduce during the same

breeding season in which they were spawned

(Hubbs 1982). Most individuals die after their

first year of life. Mense (1967) and Hubbs et

al. (1971) noted a disparity in the mortality of

males and females during the spawning season

and attributed the difference to the differing

habitat preferences of the sexes. Hubbs et al.

( 1 97 1 ) attributed the higher mortality of males

to their preference for vegetated areas, where

silverside integument damage could occur and

centrarchid predators were more common.

Inland silversides can reach 15 cm (6 in.) in

length.

Diagnostic Counts

36-44 lateral scales; 15-20 anal rays; 4-5

spines in first dorsal fin; 8-10 rays in second

dorsal fin.

Expansion

Reproduction of this species in Illinois is

likely to occur in light of its abundance in the

Ohio River. It is increasing its range in the

Mississippi River drainage south of Illinois

(Robison and Buchanan 1990), and individuals

collected from the extreme southern tip of

Illinois are probably a result of this expansion.

In other states, stocked inland silversides have

become established and abundant and will

probably do so in Illinois.

Impact on Illinois

The inland silverside appears to have had

little effect on other Illinois species. If the

inland silverside becomes abundant in Illinois,

it may compete in some bodies of water with

native species by depleting populations of

invertebrates, such as crustaceans and insects.

Gasterosteidae

Key to species of sticklebacks

1. Three dorsal spines, the last very short;

large bony plates on side (threespine

stickleback) . . . Gasterosteus aculeatus

Five to 12 short dorsal spines; no bony

plates on side 2

2. Four to 6 dorsal spines; no bony keel on

caudal peduncle (brook stickleback)

Culea inconstans

Seven to 12 (usually 9) dorsal spines; bony

keel on caudal peduncle (ninespine

stickleback) Pungitius pungitius

Gasterosteus aculeatus,

threespine stickleback

Figure 19

Origin and Range

The threespine stickleback has a circum-

polar distribution in the Northern Hemisphere

and is increasing its range in the Great Lakes

region. It is native to the St. Lawrence River

and as far west as Lake Ontario, but not in the

more western Great Lakes (Wootton 1984).

The first collections from Illinois were made in

Cook and Lake counties in 1988 (Johnston

1991). Since then, several more collections

have been made in these two counties, but none

from other Illinois counties.

Biology

The biology of the threespine stickleback

was discussed in detail by Wootton (1984).

Threespine sticklebacks are found in sluggish

waters of lakes, ponds, large lowland rivers,

estuaries, and marine coastlines. Most popula-

tions reside in an estuary or the ocean when not



March 1996 Non-native Fishes 35

engaged in spawning activities (Scott and

Crossman 1973). Freshwater populations

usually inhabit shallow vegetated water (Moyle

1976; Scott and Crossman 1973), although

large numbers of individuals are sometimes

encountered in deep water (Okada 1959-1960;

Greenbank and Nelson 1958) and at the surface

far from shore (Wootton 1984; Greenbank and

Nelson 1958). All populations spawn in fresh

water in shallow, soft-bottomed areas.

Threespine sticklebacks are visual

feeders (Wootton 1976) and feed chiefly on

microcrustaceans and insect larvae (Wootton

1984). However, essentially any food may be

consumed including algae (Wootton 1984) and

the eggs and fry of fish and conspecifics (Scott

and Crossman 1973).

Spawning in fresh water populations

usually occurs from April to the end of July,

beginning when water reaches a temperature of

14°C (57°F) (Wheeler 1969). The territorial

males prefer to build nests in sheltered areas,

even though rooted vegetation is not required

as in other stickleback species (Wootton 1984).

The tube-shaped nest is formed when the male

makes a depression in the substrate and

completes the tube with algae, twigs, and other

pieces of debris, which are held together by an

adhesive secretion produced in the male's

kidney (Scott and Crossman 1973). The male

then attempts to attract females with a courtship

"dance" that varies from swimming about

rapidly to mere side-to-side head movements

(McPhail and Lindsey 1970). If the female is

willing to spawn in the male's nest, she

assumes a vertical head-up position after which

the male swims back to the nest. The male

pokes his snout into the entrance of the nest,

presumably enticing the female to enter. If she

is ready to spawn, she enters and deposits eggs

(McPhail and Lindsey 1970). Females may
spawn more than once, and a nest may be

visited by several females. Wootton (1971)

discussed the raiding of nests by other males.

He described raiding in which a male would

lose breeding colors and make very short runs

toward another male's nest, resting on the

substrate between runs. When the resident

male detected the raider before it reached the

nest the raider was almost invariably driven off,

but when it reached the nest it usually suc-

ceeded in carrying off eggs or nest material.

Males that were already engaged in courtship

activities were never observed to raid the nests

of other males. Wootton suggested that this

raiding behavior is a result of food and nest-

building material shortages. Kynard (1979)

reported a mean clutch size of 96 eggs and an

average of 1,000 eggs in each nest. After eggs

are deposited, males remain with the nest to fan

and guard the eggs. Males guard the fry for 1-9

days after the eggs hatch (Wootton 1984).

The 1.5-2.0 mm eggs hatch in 15-20 days

at 10°C (50°F) (Wootton 1984) and in 5-6 days

at 21°C (70°F) (Kynard 1978). Fry range from

4.2 to 5.0 mm upon hatching (Kuntz and

Radcliffe 1917; Jones and Hynes 1950). After

the first year, individuals from freshwater

populations are usually from 3.0 to 4.4 cm (1.2-

1.7 in.) and individuals from anadromous

populations are around 6.0 cm (2.4 in.)

(Wootton 1984). Individuals in most popula-

tions mature after 1 year and have a maximum
life span of 3 years. Maximum size is about

7.6 cm (3 in.) in freshwater populations and

about 10.0 cm (4 in.) in anadromous popula-

tions.

Diagnostic Counts

2-4 (usually 3) dorsal spines; pelvic fin

with 1 spine and 1 ray.

Expansion

The threespine stickleback reproduces in

Illinois waters of Lake Michigan. This species

will probably increase in abundance in the Lake

Michigan area but is unlikely to infiltrate other

areas of the state.

Impact on Illinois

In some areas this species is an important

forage fish for salmonids and fish-eating birds

and, if its abundance increases, it might play

this role in Illinois as well. However, it is

known to prey on the eggs of other fishes and

may have a negative impact on native species.

It also may compete with native sticklebacks

for food and other resources.



36 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Moronidae

Key to temperate basses

1

.

No dark stripes along side of body (young

have interrupted dark lines, bars on side);

body deepest under first dorsal fin (white

perch) Morone americana

Dark stripes along side of body; body

deepest between dorsal fins 2

2. Black stripes on silver-yellow side; stripes

broken and offset on lower side; second

anal spine about as long as third; no teeth

on tongue (yellow bass)

Morone mississippiensis

Gray stripes on silver-white side; stripes not

offset on lower side; second anal spine

distinctly shorter than third; teeth on rear

of tongue 3

3. Deep body strongly arched behind head; to

45 cm (18 in.) in total length (white bass)

Morone chrysops*

Smoothly arched dorsal profile; to 2 m (79

in.) in total length (striped bass)

Morone saxatilis*

'Hybridization between the white bass and striped

bass is common. Hybrids are morphologically

intermediate between the two species.

Morone americana, white perch

Figure 20

Origin and Range

In recent years the white perch has

invaded the western Great Lakes from its native

range of Lake Ontario and the Atlantic Slope

drainages of northern North America. By 1988

the white perch had reached the Illinois waters

of Lake Michigan, and a specimen was captured

at Belmont Harbor in Chicago (Savitz et al.

1989). Recently, white perch have been

captured in the Calumet River system, the

Illinois River, and in the Mississippi River

drainage in extreme southern Illinois.

Biology

Detailed information on the life history of

the white perch was given by Mansueti (1961,

1964). The white perch is a semianadromous

schooling species found principally in brackish

water but many populations complete their life

histories in lakes and reservoirs. Coastal

populations migrate from estuaries into shallow

streams to spawn during the spring. The winter

is passed in deep water.

White perch spend the day in deeper

water and enter shallow water at night to feed

(Webster 1942b). From Chesapeake Bay

collections, Hildebrand and Schroeder (1928)

reported a diet of annelids, amphipods, isopods,

copepods, and insect larvae in individuals

smaller than 10 cm (4 in.) with fishes increas-

ingly important as food as individuals increase

in size. Freshwater studies indicate that insects,

microcrustaceans, fishes, and crayfishes are the



March 1996 Non-native Fishes 37

most important components of the diet (Reid

1972; Schaeffer and Margraf 1986; Smith

1947). Schaeffer and Margraf ( 1 986) reported

a seasonal shift to consumption of gizzard shad

(Dorosoma cepedianum) as young-of-the-year

became available in late summer and fall.

White perch feeding on the eggs of other fishes

has been reported (Bigelow and Welsh 1925;

Webster 1942a; Schaeffer and Margraf 1986).

A Maine population showed a dietary shift with

individuals under 20.1 cm (8 in.) consuming

mostly insects; those from 20.1-28.0 cm (8-11

in.) feeding equally on fishes, insects, and

crayfishes; and individuals longer than 28 cm
(11 in.) feeding chiefly on crayfishes (Reid

1972).

Spawning in white perch takes place

from May to July. Hildebrand and Schroeder

(1928) reported the capture of 10 ripe males

and 3 ripe females during December 1915, but

no other evidence of winter reproduction has

been reported. Males are first to arrive at the

spawning grounds and outnumber females there

throughout the season, although females

outnumber males away from the spawning

areas (Mansueti 1961). Spawning temperatures

range from 11-15°C (52-59°F) (Sheri and

Power 1968). Foster (1918) estimated that

10% of the population was ripe at the height of

the season with the percentage decreasing

towards the beginning and end of the season.

Spawning takes place in shallow water over a

variety of substrates. Males and females seem

to release gametes at random (Scott and

Crossman 1973). The eggs are adhesive and

become attached to the substrate and sub-

merged objects. Individual fecundity ranges

from 5,200-250,000 eggs and increases with

increasing fish length, although there is a great

deal of variation in number of eggs produced

per gram of body weight (Sheri and Power

1968).

The 0.73 mm (.03 in.) eggs hatch in 6

days at 10.6-1 1.9°C (51-53°F) (Hildebrand and

Schroeder 1928), but can hatch in as little as 30

hours at 20°C (68°F) (Scott and Crossman

1973). Larvae and eggs are not sensitive to

high levels of suspended sediments (Morgan et

al. 1983).

Growth is rapid during the first 2 years

and slows greatly thereafter. St. Pierre and

Davis (1972) found more rapid growth in

females than males until age 5, possibly due to

earlier maturation in males. St. Pierre and

Davis (1972) found the following average

lengths from the James River of Virginia: 7.6

cm (3.0 in.) at 1 year, 12.0 cm (4.7 in.) at 2

years, 14.9 cm (5.9 in.) at 3 years, 17.2 cm (6.8

in.) at 4 years, 18.9 cm (7.4 in.) at 5 years, 20.4

cm (8.0 in.) at 6 years, 22.0 cm (8.7 in.) at 7

years, 23.6 cm (9.3 in.) at 8 years, 25.3 cm
(10.0 in.) at 9 years, and 26.2 cm (10.3 in.) at

10 years. Similar values were reported from

the York River in Virginia (St. Pierre and Davis

1972) and the Patuxent River in Maryland

(Mansueti 1961). Mansueti (1961) found an

inverse relationship between population density

and growth, and first-year growth was nega-

tively related to spring rainfall. In Lake

Ontario about 8% of males were mature after 1

year and all were mature at 2 years, while about

6% of the females were mature after 1 year,

76% were mature at 2 years, and all were

mature at 3 years (Sheri and Power 1968).

Males can mature at lengths near 8.0 cm (3.15

in.) while females begin at lengths near 9.0 cm
(3.5 in.) (Mansueti 1961).

Females appear to live longer than males

(Mansueti 1961; St. Pierre and Davis 1972;

Sheri and Power 1 968), although Wallace

(1971) found the opposite result. St. Pierre and

Davis (1972) suggested the preponderance of

females among older fish might be attributable

to sex reversal. In Lake Ontario, females

outnumbered males at all age classes with an

increasing disparity in older fish, suggesting

higher mortality for males (Sheri and Power

1968). The oldest recorded white perch was 17

years old but in most populations the maximum
age is about 10 years, with females living

longer than males. Maximum size is 58 cm (23

in.); adults rarely exceed 24 cm (9.5 in.).

Diagnostic Counts

9 spines in first dorsal fin; 1 spine and

11-14 rays in second dorsal fin; 3 anal spines;

9-10 anal rays.



38 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Expansion

The white perch is reproducing in Illinois

and rapidly expanding its range. It is likely to

become statewide in distribution.

Impact on Illinois

White perch are considered game fish in

some areas, and the species may be promoted

as a sport fish in Illinois. The effect of the

species on Illinois ecosystems depends largely

on its abundance. If it becomes common in

Illinois, it is likely to compete with two closely

related native sport fishes, the white bass and

yellow bass.

Morone saxatilis, striped bass

Figure 21

Origin and Range

The striped bass is an anadromous

species native to the eastern coast of North

America, where it inhabits marine and coastal

waters, estuaries, and large rivers. This widely

introduced species first appeared in Illinois in

1974 as an escapee from impoundments in

western Kentucky, where it had been estab-

lished (Smith 1979). Today, striped bass are

regularly captured from the lower Mississippi

and Ohio rivers and several captures have been

reported from the Illinois River.

Biology

All aspects of striped bass biology were

summarized by Setzler et al. (1980). Most

studies indicate a high degree of piscivory in

striped bass once the juvenile stage is reached

(Hildebrand and Schroeder 1928; Manooch

1973; Hollis 1952; Trent and Hassler 1966);

however, invertebrates are consumed in large

quantities when they are abundant and fish are

scarce or difficult to catch (Schaefer 1970;

Rulifson and McKenna 1987). Most studies

indicate that soft-rayed fishes, especially

clupeids, are the most commonly consumed

prey of striped bass in marine (Manooch 1973)

and freshwater habitats (Ware 1971; Stevens

1958; Trent and Hassler 1966). The most

commonly consumed invertebrates are crabs,

shrimp, and amphipods (Manooch 1973). Fry

feed on invertebrates, especially copepods and

cladocerans (Harrell et al. 1977). Juveniles

feed on fish (Hollis 1952; Manooch 1973) and

whatever invertebrates are most available

(Rulifson and McKenna 1987). Stevens (1958)

found that striped bass in the Santee-Cooper

Reservoir of South Carolina fed almost entirely

on gizzard shad (Dorosoma cepedianum) and

threadfin shad {Dorosoma petenense) except in

the spring, when they shifted to mayflies.

Seasonal diet shifts can result from differential

prey availability (Hollis 1952). Bigelow and

Schroeder (1953) observed that striped bass

tend to focus on one abundant prey item and

ignore others.

Manooch (1973) found that while prey

that are about 20% of the bass' length are

preferred, individuals up to 60% of the

predator's length are sometimes eaten. Most

feeding takes place at night (Bigelow and

Schroeder 1953).

Spawning usually takes place in rapids in

fast-water streams. Individuals from anadro-

mous populations tend to move far enough

upstream to be well above the tidal influence

(Scott and Crossman 1973). Some females

return to the stream from which they were

spawned but males do not (Chapman 1989).

VanCleve (1945) and Hassler (1958) suggested

that spawning success is dependent upon river

flow, with high flow yielding better reproduc-

tive success. Spawning takes place near the

surface (Raney 1952; Hildebrand and

Schroeder 1928) where a female may be

surrounded by many males (Merriman 1941).

Eggs are broadcast into the current. The season

begins in mid-February in Florida and runs

until July in Canada (Setzler et al. 1980).



March 1996 Non-native Fishes 39

Spawning usually begins when water tempera-

ture reaches about 14.4°C (58°F) and peaks at

temperatures from 15.6-18.3°C (60-65°F).

Feeding ceases during spawning. Eggs and

larvae can survive at temperatures ranging from

13-24°C (55-75°F) (Albrecht 1964). Female

fecundity estimates range from 14,000 (Raney

1952) to 40,507,500 (Jackson and Tiller 1952).

Eggs are normally 1 .2 mm in diameter

when released into the water, but they soon

increase in size until the diameter is about 3.6

mm. Eggs hatch in 70-74 hours at 14.4-15.6°C

(58-60°F), 48 hours at 19.4°C (67°F), and 30

hours at 21.7-22.2°C (71-72°F) (Bigelow and

Schroeder 1953). Eggs are semibuoyant and

require a current of about 30.5 cm/s (1 foot/s)

to remain suspended in the water column

(Albrecht 1964). Larvae and eggs do not seem

to be sensitive to high levels of suspended

sediment (Morgan et al. 1983); however, those

that sink to the bottom have a greatly reduced

probability of hatching. Eggs seem to survive

best at moderate levels of salinity, such as those

that might be encountered in an estuary

(Albrecht 1964). Feeding usually begins about

the sixth day after hatching (Harrell et al.

1977). In Chesapeake Bay young tend to

remain in the natal estuary until the age of 2

years (Chapman 1989). Striped bass begin to

school early in life and do so until they attain

large sizes at which time they forage singly or

in small groups (Bigelow and Schroeder 1953).

Growth was measured in individuals

collected from the Roanoke River of North

Carolina by Trent and Hassler (1968). Average

fork length for males was 42.4 cm (16.7 in.) at

3 years of age, 46.4 cm (18.3 in.) at 4 years,

and 50.3 cm (19.8 in.) at 5 years. Females

averaged 51.3 cm (20.2 in.) at 4 years, 54.4 cm
(21.4 in.) at 5 years, and 60.2 cm (23.7 in.) at 6

years. Sexual maturity is often reached at an

earlier age by males and is reached more

rapidly in both sexes at higher water tempera-

tures. Almost all males are mature at 2 years in

most populations (Ware 1971; Raney 1954) but

age at maturity varies more for females. Lewis

(1962) found that females began to mature at 3

years in the Roanoke River, North Carolina,

and Jackson and Tiller (1952) found that they

began to mature at 4 years in the Chesapeake

Bay; however. Bason (1971) found that no

females were mature before their fifth year.

Minimum lengths at maturity are 43.2 cm (17

in.) for females (Clark 1968) and 17.4 cm (6.9

in.) for males (Raney 1952). Females live

longer than males. Few males exceed 1 1 years

of age (Setzler et al. 1980), but a female from

Rhode Island was estimated to be 29-3 1 years

old (Merriman 1941). Striped bass can become

very large with weights up to 56.8 kg (125 lb)

reported; they often reach lengths above 76 cm
(30 in.) and have been reported up to 2 m (79

in.).

Hermaphroditism has been reported for

Oregon populations of the striped bass that

originated from the California population

established in the late 1800s (Morgan and

Gerlach 1950; Schultz 1931; Moser et al.

1983). Young hermaphrodites have functional

sperm and immature ovaries; older hermaphro-

dites have functional ovaries.

Diagnostic Counts

9 spines in first dorsal fin; 1 spine and

1 1-14 rays in second dorsal fin; 3 anal spines;

9-13 (usually 11) anal rays.

Expansion

Illinois reproduction of striped bass

occurs in the Ohio River where young have

been collected in large numbers (Brooks Burr,

pers. comm.). Reproduction in other Illinois

rivers has not been documented, but the

potential exists for this species to become

established in large rivers statewide.

Impact on Illinois

Striped bass attain a very large size and

are highly sought game fish. However, their

predation on other fishes, including other game

species and threatened and endangered species,

could have undesirable effects on native fish

communities. Presently, striped bass are not

common enough in Illinois to be an important

game fish or to have caused noticeable effects

on other aquatic ecosystems.



40 Illinois Natural History Survey Bulletin Vol. 35 Art. 1

Gobiidae

The only goby established in Illinois is the

introduced round goby.

Neogobius melanostomus, round goby

Figure 22

Origin and Range

The round goby is native to the Black and

Caspian seas and their drainages. It was

collected in 1990 in the St. Clair River,

Michigan, and was first collected in Illinois in

1993 in the Calumet River drainage. It is now
established and rapidly spreading north and

east along the shores of Lake Michigan. It is

not known whether the Illinois population is

derived from the one in the St. Clair River or if

it was transported here directly from Europe in

the ballast water of a ship.

Biology

Throughout most of the year, the round

goby occurs in rocky inshore areas of the Black

and Caspian seas but overwinters in deeper

water (Miller 1986). Round gobies are benthic

and are capable of attaching themselves to hard

surfaces with their fused pelvic fins that are

modified into a suctorial disc. The diet

comprises mostly bivalves, amphipods, and

polychaetes; midges, small fishes, and fish eggs

also are consumed (Jude et al. 1992).

Spawning usually occurs in May and

June (Berg 1964). The following information

was taken largely from Jude et al. (1992).

Individuals spawn up to six times each season,

about every 18-20 days. The adhesive eggs are

deposited between rocks (Breder and Rosen

1966) and guarded by the male. Fecundity

ranges from 328 to 5,221 eggs per female, with

the average near 1,000 (Berg 1964). Eggs are

large, measuring about 3.9 x 2.2 mm (Jude et

al. 1992).

Round gobies can become mature at 1

year of age (Berg 1964). Males commonly

reach 18 cm (7.1 in.) and females typically

reach 14 cm (5.5 in.). The maximum size is

about 30 cm (11.8 in.).

Diagnostic Counts

49-55 lateral scales; 5-6 dorsal spines;

16-17 dorsal rays; 18-19 pectoral rays; 6 pelvic

rays; 11-13 anal rays.

Expansion

Since its first collection in Illinois in

1993, this species has become abundant in

some areas. It is found in large numbers in the

southwestern portion of Lake Michigan in

Illinois. Its ability to survive in Illinois rivers is

unknown, but it often ascends rivers in its

native range and has survived in the St. Clair

River of Michigan and the Calumet River of

Illinois.

Impact on Illinois

The round goby is a benthic species

known to eat eggs and young fish and is

thought to have caused reductions of native

sculpins in the St. Clair River. In Illinois it will

probably have a detrimental effect on native

sculpins and possibly on other native benthic

species. On the positive side, the round goby is

known to have caused localized reductions in

zebra mussel populations in Lake Michigan (E.

Marsden, pers. coram.). This species is

commercially important in its native range

where it is harvested for human consumption.



March 1996 Non-native Fishes 41

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Aliev, D.S. 1976. The role of phytophagous

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Anderson, E.D., and L.L. Smith. 1971. Factors

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Berg, L.S. 1964. Freshwater fishes of the

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Berry, F.H., M.T. Huish, and H. Moody. 1956.

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Berry, P.Y., and M.P. Low. 1970. Comparative

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