Bulletin


STATE OF ILLINOIS 


DEPARTMENT OF REGISTRATION AND EDUCATION 


DIVISION OF THE 


NATURAL HISTORY SURVEY 

STEPHEN A. FORBES, Chief 

Vol. XIII. BULLETIN Article XV. 

The Small Bottom and Shore Fauna of the 

Middle and Lower Illinois River and 


its Connecting Lakes, Chillicothe to 

Grafton: its Valuation; its Sources 


of Food Supply; and its Relation 

to the Fishery 


BY 

ROBERT E. RICHARDSON 

PRINTED fJY AUTHORITY OF THE STATE OF ILLiNOIS 

URBANA. ILLIN OIS 


June, 1921 




ERRATA
Page 97, line 17, for first larval read puital.

Page 112, in legend, for jonessi read jonesii.

Page 114, in legend, for or read of.

Page 125, line 4, for Bonosa read Bonasa.

Page 131, in legend, for Jiirundinaceus read hirudinaceus.

Page 138, last line, for coccoon read cocoon.

Plate XII, explanation page, next to last line, for acrivora read aerivora.

Plate XIII, explanation page, next to last line, for WMte-gruhs read White-gruh.

Page 293, Figure 5a was reversed in printing, and the two items of the legend

should change places.

Page 515, second table, for Pelocoris femorata read Pelocoris femoratus.



Article XV.

—

The Small Bottom and SJiore Fauna of the Middle
and Lozver Illinois River and its Connecting Lakes, Chillicothe to Graf-
ton: its Valuation; its Sources of Food Supply; and its Relation to the

Fishery. By Robert E. Richardson.

Introduction

The present paper, so far as it relates particularly to the valuation of
the bottom and shore animals, brings together the results of three sum-
mer-autumn seasons of dredging operations in the Illinois River and its

connecting backwaters, July, 1913, to October, 1915. The work in the
river proper and in the wide expansion of its waters known as Peoria
Lake included forty cross-sections at intervals ranging from one to about
eleven miles, covering the lower one hundred and eighty miles of the
river, or about 80 per cent, of the total distance between the mouth and
the head of navigation at La Salle ; and embraced a total of three hundred
and eighty-seven dredge and dipper collections. The dredging opera-
tions in the more inclosed bottom-land lakes were mainly confined to

those in the middle Illinois valley district of about fifty-nine miles river

length between the Copperas Creek and Lagrange dams, in the lakes and
other backwaters of which region three hundred and eighty-five dredge
and dipper hauls were taken during the three working seasons.

In addition to the collections of the bottom animals for the valua-

tion studies, sieved samples of the mud deposits on the floor of both the

river and the lakes were taken in 191.3 and 1914 and analyzed for such
indications as they might contain of reasons for dilTerences in productiv-

ity of different bottom areas. Between March, 1914, and February, 1915,

also, standard sanitary chemical analyses of water samples from a lim-

ited number of stations in the upper, middle, and lower river were car-

ried on continuously at weekly intervals with a view particularly to

obtaining data on the nitrogen load of the waters and on the rate of

progress of its nitrification. Such comparisons as are undertaken with
plankton production are with reference mainly to data collected in 1909
and 1910, the most recent seasons devoted at all extensively to plankton
operations in the region of the river covered by the present paper. Some
principal conclusions from the plankton work of these two years in the

river and'lakes at Havana, as also from the sanitary chefliical analyses of

1914-1915, have already been reported upon in papers by Prof. Forbes and
the present writer (Forbes and Richardson, 1913; 1919).

Apparatus.—The collection of the bottom fauna was begun in the

summer of 1913 with our ordinary iron dredges (modified "Blake" or



364

"Naturalist's" type (see pages 367, 368), supplemented in some situa-

tions where there was unusually soft mud and where the heavier framed
iron dredges were inclined to sink too deeply and fill too quickly, with a

lighter framed dredge following closely a recent design by Ekman which
was intended for quite a different purpose. (See Fig. 3 and 4.)

Although there was no expectation early in the work of making
more than a very rough quantitative application of the biological data

obtained, all the dredge hauls were, from the first, of a previously de-

termined and recorded length. The introduction into use in the summer
of 1914, for work in water under eighteen feet in depth, of the "mud-
dipper" (see Fig. 5), an instrument bearing some resemblance to

the Walker dipper-dredge as used by Baker (1916, 1918), and the adop-

tion of finer meshed inner bags for it and the dredges, was the means of

what appeared to be rather more accurate work that year than in the

first season, while at the same time its use in parallel test hauls of differ-

ent lengths alongside the iron dredges suggested that averaged results

from measured drags, under certain limits of length, with either, had a

greater quantitative value than we had at first believed. It was found,

in brief, that with a 22" X 6" front iron dredge we took on the average

as many bottom animals by hauling five feet as by hauling ten, and with

a 6-inch mud-dipper as many in two feet as in four, but that

in hauls under two or five feet, in either case, we got less. As the aver-

age 5-foot haul with the dredge was in the neighborhood of ten times the

2-foot drag of the dipper, and the 2-foot dipper haul about five times a

quick deep dip of the mud-dipper to a depth of about three inches (ap-

proximate area covered, 25 square inches), it was an easy step to the con-

clusion that on a rough average, if a few apparently aberrant cases be

excluded, the most of the 5- to 10-foot dredge hauls might be safely

taken to represent an effective drag of about one square yard, and the
2- to 4-foot hauls of the dipper an effective drag of about 0.1 square

yard (125 to 130 square inches). Still more recent parallel tests of the

dipper alongside a new Petersen self-closing bottom sampler have not

served materially to change these conclusions.

The method used for collecting the small weed animals in the zones
of densest vegetation (usually in water under four feet deep) was in-

complete, taking in only the small fauna within the to 9-inch depth line.

A large bucket of known depth and diameter was lowered about the tops

of the plants, the stems were cut off underneath, and then the bucket

was brought into an upright position quickly ; after which the weed-tops
were shaken out in the water saved, and that was finally passed through
a 120-mesh sievt. Pulling up the weeds entire in water over two and a
half feet deep had shown that the attached weed animals, whether snails,

insect larvae, or Crustacea, were, in bulk at least, decidedly most abun-
dant nearer the top. And the adoption of the method also followed, by
necessity, some unsatisfactory experience in the use of a small 3-legged

caisson and pump—which involved the handling of vastly more material



365

than was practicable, with also an annoying tendency to in-leakage of

outside water at the bottom.

Valuation.—The determination to undertake a valuation of the bot-

tom invertebrate populations that come within the feeding horizon of our
ordinary bottom-feeding fishes in terms of pounds pet acre was made
some time after the conclusion of our field work in 1915, and has been

carried out on a basis of estimated average-sized specimens of the va-

rious species as they ran in a relatively small number of typical midsum-
mer collections weighed after more than a year's preservation in alcohol

and formalin. An average correction of 25 per cent, for loss in weight
in alcohol (on a base of body weight only for Mollusca, and on a base

of gross weight for other groups) has been made, after a limited number
of experimental weights, in the preserved and the fresh state, of a few
snails and insect larvae. The final valuation figures, so far as they in-

clude insects, their larvae or other immature forms, worms, or Crustacea,

represent gross rough weights, but in the case of the Mollusca (Gastrop-

oda, Sphaeriidae, or young Unionidae) represent the body weight only,

after deduction of shell weights at rates determined separately for each

species by actual weighing. Sponges, Bryozoa, and other smaller in-

crusting invertebrates are not included in the valuation figures ; as are not

also crayfish or pearl-button mussels, except the young.

Acknowledgments.—For many of the hydrographical and physical

data we are indebted to the U. S. Army Engineers' survey of 1902—1905

(House Document 263, 59th Congress, 1st session, and accompanying
charts) ; as well as to Alvord and Burdick's recent excellent report

(1915) on the Illinois River and its bottom-lands; and, in a lesser de-

gree, to the Report of the Legislative Committee on submerged and shore-

lands (1911). Thanks are also due Dr. Edward Bartow, Chief of the

State Water Survey, for his interested cooperation in obtaining the san-

itary chemical analyses of river waters in 1914; and to Prof. S. W. Parr

for supervising the analysis of the bottom mud samples taken that year

and the year preceding. To Mr. Charles A. Hart is owing a special debt

for his assistance in the determination of much of the more unfamiliar

biological material of the earlier collections, taken in the preliminary

field work of July-September, 1913. Mr. F. C. Baker has contributed

both facts and opinions that have made possible rough valuations, for

comparison with our own, of the littoral bottom fauna areas of the lower

south bay of Oneida Lake, New York, reported upon by him in two very

interesting and valuable papers in 1916 and 1918. To these two papers

and to Dr. C. G. Joh. Petersen's several recent contributions on the valua-

tion of sea-bottom ofl^ the Danish coast (Reports of Danish Biological

Station, 1911-1918), I owe not a few ideas which have cast illumination

in more or less dark places. The general plan into which the present

piece of work is intended to fit, the directing force behind it, and the sup-

ply of means and general suggestions as to methods for its execution,

have been the work and care for many years of the Chief of the Natural



366

History Survey, Professor Forbes, without whose aid in these more pro-

foundly important respects the present investigation would doubtless

neither have been conceived or carried out in its present scope and form.

Illustrations of Apparatus.—Fig. 1. Iron dredge, showing canvas

protector covering posterior bobinet bag, and forward coarse-mesh bag

hung backward inside.

Fig. 2. Iron dredge, showing canvas protector rolled back to un-

cover bobinet bag; and forward coarse-mesh bag pulled out in front of

frame.

Fig. 3. Ekman dredge, showing canvas protector covering pos-

terior bobinet bag, and forward coarse-mesh bag hung backward inside;

front mud shoes of Ekman design omitted.

Fig. 4. Ekman dredge, disposed as iron dredge in Figure 2.

Fig. 5. Mud-dipper, showing bobinet bag pulled out in front of

thimble, and canvas protector in position for drag.

Fig. 6. Apparatus used in 191-1: for collecting samples of the thin

bottom ooze for study of the composition of the lighter detritus and the

microorganisms entering into the food supply of the small bottom animals.

General Summary

It is the purpose of the studies here reported to make an estimate,

based on many quantitative collections, of the total store of animal life on

and in the bottom sediments of different sections of the middle and lower

Illinois River and its bottom-land lakes and on the plants of their shal-

lower, marginal waters, to trace the causes of the wide diflferences in this

respect between river and lakes and between different sections of the

stream, to estimate, also quantitativly, the- food resources which the bottom
muds contain for the animals inhabitating them, and thus to trace in a gen-

eral way the successive steps by which the organic materials in the muds
and waters of the river system are converted into forms available as food

for man. This is, in fact, to be regarded as essentially a soil survey of

these aquatic public properties, for the beds and weedy margins of rivers

and lakes are a natural soil of various fertility, of which the animals,

mainly univalve mollusks and a few kinds of insect larvae, are the crop,

harvested chiefly by fishes, these being harvested in turn by man. From
this point of view the upper Illinois River is, under present conditions,

mainly a mass of plant and animal weeds—forms which occupy the pol-

luted waters to the practical exclusion of everything useful to human
kind—but the current of this section carries elements of a normal fertility

to the lower reaches of the river, depositing a large part of them finally

in the silts and sediments of river and lake in forms available for the

nutrition of normal aquatic life, but bearing also an immense quantity

to the mouth of the stream where it escapes unutilized into the Mississippi.

The river system below Chillicothe varies enormously in the produc-

tiveness of its different parts, the richest of them being the weedy margins



3
6
7

S
o

u
^



3
G
8



3
6
9



3
7
0



371

Fig. 5. Mud-dipper, showing- bobinet bag pulled out in front of thimble,
and canvas protector in position for drag.



3
7
2



373

of the shallower lakes, and the poorest those sections of the river channel
which are swept comparatively bare of sediments by a relatively swift
flow. In the river itself much the most abundant product is found where
the current is most sluggish, and the bottom sediments are consequently
deepest and are most heavily charged with organic materials originallv

washed into the stream by rains or poured into it by sewers of cities and
towns and transformed by oxidation into compounds suitable for the
nutrition of clean-water plants and animals.

In a stretch of the river above Havana, which, with its adjacent
lakes, is the richest part of the Illinois River system, the inshore and
bottom fauna of the lakes averages in weight to the acre about twice as
much as that of the river, and it is in the lakes that the fisheries give their

highest yield. The bottom soils of the lakes are, indeed, richer in or-

ganic matter, as a rule, than are those of the river opposite, and the muds
of the marginal waters of these lakes are richer than those of their deeper
parts—facts traceable, in part, no doubt, to the more abundant light and
higher temperature of the shallower waters and the consequent greater

growth of plants whose decay enriches the soil from which they sprang.

At ordinary high-water levels the current of the river from Chilli-

cothe to the mouth varies from one to two miles per hour according to

the slope of the bottom, the width of the bed, and the presence or absence
of obstructions ; and at the highest water it does not much exceed three
miles per hour for any important distance. At ordinary midsummer levels

the current rate per hour varies in different sections from half a mile to

a mile. At lowest water it drops, between Chillicothe and the foot of

Peoria Lake, to as little as .29 mile per hour.

Above Havana the bottom, both along the shores and in the channel,

is, with some exceptions, a rather deep black mud, but below Havana
this shades gradually into hard clay or sand and shells, soft mud failing

completely in the channel for long distances. The quantity of inshore

vegetation is negligible in the river proper, even in the driest seasons,

since the opening of the sanitary canal of the Sanitary District of Chicago
in 1900. The bottom-land lakes between Copperas Creek and Lagrange
are gradually filling with river silt and a growth of plants. A few have
sandy beaches next the eastern bluffs, but the bottoms of all are otherwise
of deep black mud, mixed in the shallow water along shore with coarse

rotting vegetation. In midsummer the margins of all the deeper lakes,

to a depth of four to six feet, are well supplied with vegetation, while the

shallower lakes are in many cases weedy over their entire acreage.

From Chillicothe to Lagrange the animal life of both channel and
shore waters is almost wholly mollusks (86 to 99 per cent, in collections

made), but below Lagrange insect larvae (caddis-worms and May-fly
larvae) were more abundant than above in the shore muds, the ratio of

mollusks falling to 31 to 65 per cent. In the deeper, opener lakes, mol-

lusks made 77 to 96 per cent, of the collections, and in the shallower, more
weedy lakes, 36 to 79 per cent.



374

Speaking generally, the richest sections of the river floor are those

with the least average slope and the slowest current, and therefore with

the most abundant sediments. The quantity of the bottom fauna dimin-

ishes rapidly down-stream from Chillicothe, averaging 555 pounds to the

acre for the upper sixty miles (the weight of the shells of the moUusks
being in all cases deducted), SS pounds for the forty-two and a half

miles next following, and 10.4 pounds for the lower seventy-seven miles.

The general average for the river channel from Chillicothe to the mouth
^

was 261 pounds per acre. That for Copperas Creek to Lagrange, within

which section lay the twelve principal lakes studied, was 705 pounds per

acre, and the highest sectional yield was 2,f)93 pounds per acre between

Copperas Creek and Havana. The highest local yield was found in the

lower half of this Copperas Creek-Havana section, whose channel prod-

uct rose to 5,196 pounds per acre. These enormous yields in the

stretch above Havana were evidently due, at least in great measure, to

the sluggish current and consequent heavy sedimentation and to the

great predominance (99 per cent.) of relatively large, thick-shelled snails,

edible only by the larger fishes, armed with a powerful crushing apparatus

in jaws and throat.

In the muddy section of river above Havana the channel yields ap-

proximated or even surpassed those of the shallow waters along shore;

but below Havana, where mud is largely replaced by sand, clay, or shells,

the channel yields were only 5 to 10 per cent, those of the longshore

zone.

Comparing river and lakes between Copperas Creek and Lagrange
(59.3 miles) we find that the average bottom yield per acre of twelve

lakes examined was about one third that of the river opposite them,

but that it was practically the same as the average for the entire river

from Chillicothe to the mouth. The deeper lakes with sandy beaches at

one side yielded about twice as much per acre as the shallower lakes with

mud banks all around.

In the deeper bottom-land lakes surrounded by mud banks, the shore

belt, to a depth not exceeding six feet, yielded about three times as much
bottom fauna per acre as the deeper open water of these lakes; but in

the sand-beach lakes this relation was reversed, the deeper bottom yield-

ing five or six times as much as that within the 6-foot line.

The foregoing statements all apply to the animals living in or on

the bottom muds ; but in the shallow, weedy areas of lakes and back-

waters the small invertebrate animals living on and among the weeds
greatly exceed both in number and in weight per acre the fauna of the

bottom itself, aggregating in many collections made near Havana in 19l4,

from 1,100, to nearly 2,600 pounds per acre, with an average of 3,118

pounds—quantities to be compared with an average of 255 pounds of

bottom fauna per acre from the lakes of the same district.

Combining weed and bottom faunas of our collections and applying

their joint averages to the entire area of lake and backwater between



375

Copperas Creek and Havana, we get a yield of 1,447 pounds per acre, to

be compared with 705 pounds per acre for the unusually rich sections of

the river opposite.

From analyses of the bottom muds of the river channel and esti-

mates of the nitrogen content of total bottom fauna per acre, it appears

that the nitrogen in the river sediments is many hundred times the nitro-

gen content of the flesh of the animals living in them, and that the total

dry organic matter in the channel muds is several thousand times the

dry weight of this bottom fauna.

Chemical analyses show that the bottom soils of the lakes are richer

in organic matter than those of the river opposite them, and that in the

lakes themselves the bottom soil is richer near the shore than at the center.

The plankton of the river passing Havana in a year amounts to about

200,000 tons live weight, equivalent to four thousand to ten thousand

tons dry weight. This is, roughly, 20 to 50 times the total dry weight of

the flesh of the animals of the bottom muds of the lakes from Copperas

Creek to the mouth, a distance of 138 miles.

An estimated total of 600,000 tons dry weight of organic matter,

suspended and dissolved, passed Chillicothe in 1914. This is 60 to 150

times the dry weight of the plankton that passed Havana in twelve

months (1909 and '10), and 3,000 times the dry weight of the total bot-

tom fauna of 1915 from Copperas Creek to the mouth of the river.

The dry weight of nitrogen in the above organic matter was sufficient to

replace the nitrogen in the plankton of a year from 92 to 232 times.

The plankton per cubic meter of water was greater throughout the

year in Thompson Lake than in the river opposite in 1909 and '10, the

difi^erence being greatest at times of lowest production (midsummer and
winter) in both river and lake.

The river plankton is constantly settling to the bottom to an impor-

tant degree, as is shown by the composition of the bottom ooze and by

the stomach contents of small invertebrates living on and in it. In June,

1914, living, moribund, or recently dead limnetic plankton was more
abundant in the upper layers of the ooze than the normal bottom plank-

ton or old organic detritus, as was shown by the food of Sphaeriidae,

Trichoptera, and Chironomidae, and it made also an important part of

the food of large detritus-eating gastropods (Viviparidae, Pleuroceridae,

etc.).

There is a much greater loss of plankton down-stream than can be

explained by dilution merely. The falling oflf in plankton per cubic

meter between Havana and Grafton amounted, during nine months of

the growing season, to approximately 62 per cent., notwithstanding the

normal rate of multiplication of the planktonts as they passed down
stream. These losses were greatest when the current was slowest and

settling consequently easiest. They were not due to lack of food, because

the percentage of nitrogen and the nitrates increased from Havana down-

ward.



376

In our opinion and that of the most intelHgent and observant fisher-

men, the lakes are, the favorite feeding grounds of the larger and more
common fishes, and this opinion is supported by the fact that the lakes

have a more abundant food supply per acre than the river, and that the

heaviest fish-yields come from sections where the ratio of lake areas to

river is greatest.

The average weights of the yields of the inshore bottoms of the

Illinois River lakes in 1915 were about five times as great per acre as

those of the glacial lakes of northeastern Illinois in 1916, and the com-
position of the faunas was also widely different, mollusks occurring in

the latter in relatively insignificant proportion and being nearly all of

the smaller species. The weed faunas of Fox and Pistakee lakes were
almost wholly made up of small crustaceans and insects, the former
predominating, although the total weights were not very much less than

those of the Illinois system.

Hydrography and Bottom Fauna, Illinois River,

Chillicothe to Grafton, July-October, 1915

(aj Chillicothe to Foot of Peoria Lake (18.5 Miles)

Hydrography.—If the Illinois River is a sluggish stream considered

as a whole, in comparison with most other important American rivers,

the grand prize for local leisureliness of movement belongs to the short

stretch between Chillicothe and the lower end of Peoria Lake, where,

in March, 1903, at a Hood stage of approximately eighteen feet above
old low-water marks at Peoria, it took ball floats twenty-nine hours and
fifty-nine minutes to make a total distance of 17.7 miles, the average rate

per minute being 51.94 feet, and per hour, 0.59 mile. At a gage of nine

feet, Peoria, which is almost exactly the mean level of the month of

August, 1914, and represents the lowest water in this part of the river

in the past seven years, these rates would be reduced to 25.97 feet per

minute or 0.29 mile per hour—a total time in transit of fifty-nine hours

and fifty-eight minutes for the 17.7 miles.

These velocities compare with an average of 229.47 feet per minute
or 2.60 miles per hour at a corresponding flood gage for the 3.3.9 miles

Morris—Utica ; and with 115.43 feet per minute or 1.31 miles per hour
for the 229.6 miles between Utica and Grafton. Above Peoria only

the 12-mile section Henry—Hennepin has a current approaching the low
figures found between Chillicothe and Peoria. In the other short reaches

above Peoria, and in all below Peoria except the section of 8 miles between
Liverpool and Havana (with 66.00 feet per minute, or 0.75 mile per
hour), average flood velocities are over 100 feet per minute (1 mile per
hour). The greatest velocities below Utica occur in the 9.8 miles between
Peoria and Pekin (with 191.64 feet per minute or 2.17 iniles per hour)

;

and in the reaches below Florence, which have over 180 feet per minute,
or more than 2 miles per hour.



377

Table of Approximate Average Velocities, Illinois River

This taHe is hased on float records of J. L. Tan Ornum, as published in

Water Supply Paper No. 194, V. S. Geological Survey, 1007, pp. 17-18.

(The gage at Peoria averaged about eighteen feet during the tests. The
figures for nine feet are one half the 18-foot figures, various measurements by

the U. 8. Geological Survey and others showing about 50 per cent, decrease in

velocity between approximately these gages at Peoria and corresponding gages
at other stations.)



378

Decline in Elevation of Low-Water Surface, 1901

Reach



379

Widths and Depths, Chiixicothe to Foot of Peoria Lake,
Low Watee, 1901

Miles above
Grafton

Width,
ft.

Depth,
ft.

max.

1S0.2

179.6

Unwidened river—
500 yds. below boat-landing, Chillicothe

Foot Chillicothe Island
494
439

24.0

22.5

17S.4

177.9

175.5

Upper lake—
Head Peoria Lalve, one half mile above Rome
Rome
One and a half miles above Spring Bay

l.OOQ



380

of the "depth to hard bottom"* ran from thirty-six to seventy-two

inches at stations between Rome and the foot of Main St., Peoria. At
the Narrows the mud was harder, lighter in color, and was mixed with

old dead shells and thickly carpeted with sponges and Bryozoa.

Depth (of Softer Mud) to Hard Bottom at Channel Stations

180.5

177.2

175.5

172.3

166.5
162.7

Chillicothe
One mile below Rome
Peoria Narrows
Opposite Mossville
One and a half miles above Spring Bay
Opposite foot Main St.

3

72

Hard bottom
48
36
36

The elevation of the bottom of the river channel eighteen miles south

of Chillicothe, instead of being lower, is actually more than eighteen feet

higher than the plane of greatest depth opposite Chillicothe ; more than

fourteen feet above the bottom plane of the deepest part of Peoria Lake
above the Narrows ; and more than two feet higher than the highest

point in the channel bottom between Chillicothe and the foot of the lake.

I think we must suppose that the way out of Peoria Lake was once much
more ope:i, and that the action of Farm Creek has been largely re-

sponsible for building up the high bar that now dams tip the entrance

into the Pekin reach. The nearness to the surface of rock between Pe-

oria Narrows and Wesley would, however, have prevented in any case

the excavation of a fast and deep channel through the Chillicothe-Pe-

oria section.

Because of the very shallow gradient, and the great expansion of

the river between Chillicothe and Peoria, the shallower backwater in

most of the distance, though not separable from the river channel by
any distinct boundary, resembles more nearly the larger inclosed bottom-
land lakes than ordinary river littoral. Except for a very short distance

at and near Peoria Narrows, the land to the eastward of the channel is

low, the banks are all of mud, and the soft bottom sediments very dark
in color. Within the 3- foot line on this side the bottom muds contain

more decayed vegetable matter than further out, and there is a good
deal of living vegetation (principally Potamogetons and Ceratophyllum)
during the dry season. On the west side of the channel, sand or gravel

or hard inud bottom is found for considerable distances out to a depth
of three to seven feet wherever the channel closely approaches the bluff.

Opposite Mossville, where the channel is east of the middle of the lake,

the 1-3- and 4—7-foot zones on the west side are very similar in mid-
summer to those on the east side first described. Except for a short dis-

* Made by forcing a 2 X 2-inch pole, square across the end, as deeply into
the mud as a strong man could with both hands.



381

tance at this place, such vegetation as grows on the west side is usually

only a thin fringe next the rather steep bank. Outside the 4-foot line

Peoria Lake has recently been almost entirely free of vegetation, even

at the lowest gages, and it is consequently much more subject to roiling

by winds than the narrower and weedier lakes near Havana.

The Bottom Fauna.—Collections of the small bottom animals, with

dredges and mud-dipper, were made in the channel July 26 to August
19, 1915, at four stations in the mud-section between Chillioothe and
Peoria Narrows ; in the hard mud at Peoria Narrows ; and in the mud
opposite the steamboat landing at Peoria.

Chanj^el Collections, Chuxicothe to Peoria Lake, 1915

Miles
above
Grafton

No. col-

lections

July-
August,
1915

Depth ad-

justed to

gage
July-
October,

1910—1914

Deep, narrow river

177.2

175.5

One mile below Rome
One and a half miles
above Spring Bay Upper lake, channel

172.3 Opposite Mossville 19 Middle lake, channel

166.5 Peoria Narrows

Opposite Eagle Packet
landing Lower lake, channel

Total channel collection^ 15

The average number of bottom animals in a square yard of channel

bottom, if we except the Peoria Narrows station (which represents a

very limited area with hard bottom), compared favorably (at 235 per

sq. yd.) with the figures from some other short reaches between Peoria

and Havana, but was under the average for the 60.5 miles (416 per sq.

yd.), and was far below the figure for the very rich section of eight

miles just above Havana (1,469 per sq. yd.). In all the collections Mol-
lusca (Gastropoda and Sphaeriidae) were much more numerous than

insects, worms, and small Crustacea ; and the larger Gastropoda (Vivi-

paridae and Pleuroceridae) were usually more abundant than the

Sphaeriidae and smaller Gastropoda (Amnicolidae, etc.).



382

Bottom Fauna, Channel, 1915

numbers per square yard, average

Viviparidae
and

Pleurocerldae

Small
Gastropoda

and
Sphaeriidae

Insects,

worms,
Crustacea

Total
Col-

lec-

tions

Chillicothe—Mossville
At Peoria Narrows
Peoria Narrows to foot ofl

Peoria Lake

88.2

23.3

143.7

1.0

5.0

26.6

13.3

258.5

37.5

Average (excepting collec-

tions at Narrows)
| |

|

The average valuation of the channel bottom fauna in pounds per

acre (shells of Mollusca deducted) in this section (285.9 poiuids, with

the Peoria Narrows station included ; 345.1 pounds, with Peoria Nar-
rows omitted) was better than the average (239 pounds) for the 43.7

miles between Chillicothe and the Copperas Creek dam, but was less

than one tenth of the channel average between Copperas Creek dam and
Havana (3,029 pounds per acre), and less than one twentieth of the

average valuation for the eight miles between Liverpool and Havana in

1915 (5,180 pounds per acre). The great bulk of the collections, by
weight (85 per cent.), was made up of the larger snails (Viviparidae and
Pleuroceridae), and these families together with the Sphaeriidae and
smaller Gastropoda accounted for about 98 per cent, of the 'average

poundage taken.

Bottom Fauna, Channel, 1915

pounds per acre, average

Viviparidae
and

Pleuroceridae

^™^"
! Insects i

Gastropoda,
'^^^^l

~

^^^^,

Sphaeriidae;
Crustacea

Col-

lec-

tions

Chillicothe to Mossville
At Peoria Narrows
Peoria Narrows to foot of

Peoria Lake



383

A total of thirty collections in the shallower areas between Chilli-

cothe and the foot of Peoria Lake were taken with the mud-dipper in

1915; ten within the 4-foot line, and twenty between the 4- and 7-foot

lines (depths adjusted to gage July-October, 1910-1914).

Shore Collections, Chillicothe to Foot of Peobia Lake, 1915

Miles above



384

4- TO 7-FOOT Zone, 1915

NUMBERS PER SQUARE YARD, AVERAGE

Chillicothe to Mossville
Peoria Narrows to foot of
Peoria Lake



385

p fe
"<

i



3S6

(b) Foot of PeorIa Lake to Pekin (9 Miles)

Hydrography.—After passing over the high bar above the mouth
of Farm Creek (foot of Peoria Lake) the river follows a comparatively

swift and narrow channel to Pekin, the average velocit)' at a flood gage
of eighteen feet, Peoria, being 191.64:* feet per minute for the 9.8 miles

between the foot of Main St. and the wagon bridge at Pekin, and the

width (at low water of 1901) usually under six hundred feet. The aver-

age slope of the water surface at the low levels of 1901 was two inches

per mile, and 4.36 inches per mile at the high water of March, 1904.

These average slopes and velocities are much greater than are met with

in any other considerable section of channel in the one hundred and
twenty-five miles between Chillicothe and Florence, and are four to

seven times the figures for the 18.5 miles between Chillicothe and the

foot of Peoria Lake.

Decline in Elevation of Water Surface

Reach



387

acreage (113.6 acres per mile at the low water of 1901) is little more
than a third of that which occurs between Chillicothe and the foot of

Peoria Lake (399.9 acres per mile) ; and is under the rating of any other

section of the river between Chillicothe and Kampsville.*

Widths and Depths, Foot of Peokia Lake to Pekin, Low Wateb, 1901

Miles above Grafton Width, ft.
Depth ft.

max.

161.9

160.7

159.9

159.0

158.0

157.0

156.0

155.0

153.9

153.3

153.0

150 yds. below mouth Farm Cr
P. &. P. U. R. R. bridge

100 yds. below Wesley

I Pekin, at wagon bridge

347



388

Pekin than above Peoria, and the Sphaeriidae less so. The larger Gas-
tropoda (Viviparidae and Pleuroceridae) made up about the same per-

centage of the average weight of collections as above Peoria (88.6%).
In the 4-7-foot zone the Sphaeriidae showed the heaviest poundages

(66.27o of totals), and the insect larvae and the larger snails v/ere rela-

tively much less abundant than in channel collections.

Bottom Fauna, 4

—

7-foot Zone, Wesley to Pekin, 1915, Average



389

Decline in Elevation of Water Surface

Reach



390

large part of the section ranged between 7 and 9 feet. Recent maximum
low-water depths have been mostly 3 to 3J4 feet more than these. The
connecting lake and pond acreage in this section at the low levels of 1901

(219.0 acres per mile) was about twice that between Peoria and Pekin

per mile of river length, but was not much more than two thirds that

between Chillicothe and the foot of Peoria Lake, and was less than half

that between Copperas dam and Havana.*
Bottom Fauna.—A total of 14 channel collections and 16 shore col-

lections were made between Pekin and the dam in 1915 at stations as

shown below.

Miles
above
Grafton



391

latter 50.6%. The insects, worms, and small Crustacea made up the re-

maining 5.7%, the greater part of which was composed of the larvae

of the commoner channel caddis-flies.

In the shore zones both numbers and weight valuations were con-

spicuously higher than in the channel, the average poundage in the

4A7-foot zone being 695 per acre and that in the 1-3-foot zone 391. Con-
trary to the rule found usually to hold good in the river, the larger Gas-

tropoda (Viviparidae principally) here showed larger poundages and
much larger percentages of valuation totals (74 to 91%) both in the

1-3- and 4—7-foot zones than did the Sphaeriidae. The insects, worms,
and Crustacea contributed less than one per cent, of the average pound-
age figures in the '^7-foot zone. In the hauls taken inside the four-foot

line, leeches and chironomid larvae were especially abundant, and these

with a few worms and small Crustacea added, made up over 8% of

the weight of the average haul.

Bottom Fauna, 4

—

7-ft. Zone, Pekin to Copperas Creek Dam, 1915



393

(d) Copperas Creek Dam to Havana (16.8 Miles)

Hydrography.—One is at first surprised to find that although at

the low water of 1901 there was a decidedly greater decline in elevation

of water surface between the foot of the dam at Copperas Creek and

Havana (o.yS inch per mile for 16.8 miles) than between Pekin and

the head of the dam {0.14 inch per mile for 16.3 miles), average flood

velocities in the section below the dam are less than in the section of

similar length above it. The average velocity at a gage of 18 feet,

Peoria, March, 1903, was 83.81 feet per minute between Banner—about

3 miles above the dam—and Havana ; and was 114.40 feet per minute

between Pekin and Banner. The average slope of high water surface,

however, is in close correspondence with these flood velocities—equal-

ing 1.43 inches per mile between Pekin and the dam, as compared with

1.18 inches per mile between the dam and Havana at a gage of 33.6 feet,

Peoria, March 31, 1904 ; and 1.36 inches per mile between Pekin and

the dam, compared with 1.11 inches between the dam and Havana at a

gage of 19.0 feet in March, 1903. As the low flood velocities through

Peoria Lake are a joint consequence of the high bar above the mouth
of Farm Creek and the unusual opportunity for expansion in the broad

and low flats above it, the retardation of the flood current between Cop-

peras Creek dam and Havana may be explained also as due jointly to

the increased impounding area in this section* and to the high mud bar,

superimposed upon an older sand bar, which attains its summit about a

mile above the mouth of Spoon River. The top of this bar has an

elevation only 0.6 foot below the level of the channel floor just below the

dam at Copperas Creek, and is 13.8 feet higher than the deepest part of

the channel between Liverpool and Havana. The artificial pool behind

the dam at Copperas Creek, on the other hand, lies toward the lower

end of a stretch of river with relatively steep natural slope, and at the

higher gages the flood water moving through that section tends to follow

the old slope-lines of water surface as they existed in the years antedat-

ing the construction of the dam.

Quite consistently with what has just been noted, both at flood

stages and at the ISTOl low levels, average slope and current are ap-

preciably greater in the first than in the second half of the 16.8 miles be-

low the dam, the average velocity (66.00 feet per minute) in the eight

miles immediately above the Havana bar at a flood gage of 18 feet,

Peoria, being in fact not much more than half that in the first eight miles

(105.01 feet) and less than that of any other considerable reach of

channel in the whole river below Peoria.

In the first seven miles of channel below Copperas Creek dam the

upper bottom stratum as shown by the government borings of 1903-1905

was sand and shells or plain sand to a depth of 4 to 31 feet for the

greater part of the distance; though dirty sand or sand and shells oc-

curred .at a few of the boring stations and was found by us just above

Table, p. 378.



393



394

and just below Senate Island in 1915. In the nine miles of deeper chan-

nel between Mile 129 (1 mile above Liverpool) and Havana, the bottom

is uniformly mud. The depth of the mud layer is nearly everywhere

more than 8 feet, and in extreme instances 13 to IT feet. The thickness

of the mud stratum diminishes to about 7 feet opposite Havana, and a

quarter mile farther south the mud quite gives way to a layer pi mud
and shells, which description of bottom continues nearly uninterrupted

for the next 14 or 15 miles. The bottom soils found in the shore zones

between Havana and Copperas Creek in 1915 were dark-colored soft

mud throughout the 16.8 miles.

Between the dam and Liverpool, bank to bank widths at the low

water of 1901 were much as between Pekin and Copperas Creek

—

usually 550 to around 700 feet ; while the greatest depths were under 12

feet. Below Liverpool the river narrows and deepens decidedly, as far'

as Mile 122.4—the beginning of the expansion formerly known as

Havana Lake. In this six miles, widths at the 1901 low levels ranged

from 329 to about 500 feet, and depths from 14 to 21 feet. Opposite

Havana, for a distance less than half a mile above the mouth of Spoon
River, the wide water spread over the Havana bar (Havana Lake)

showed an extreme width in the summer of 1901 of about 1,300 feet;

while maximum channel depths in the 3 miles above Mile 121 (1 mile

above Havana) tapered ofif southward from more than sixteen to about

seven feet. Recent extreme depths at midsummer low gages in the

lower half of this reach have ranged from 4 to 5 feet more than the

low-water depths given.

Widths and Depths, Copperas Creek Dam to Havana, Low Water, 1901

Miles
above
Grafton

Station Width, ft.
Depth, ft.

max.

136.6

136.0

134.3

133.0

132.5

129.S

129.0

128.5

128.0

126.9

126.5

126.0

125.7

125.4

125.0

124.0

123.0

122.4

121.0

120.0

500 yards below dam.

1 mile below foot Senate Island

1 mile above Liverpool

Liverpool

5 miles above Havana. . .

.

Middle of "Hogfat Bend".

Upper end "Havana Lake".
C. P. St. L. Piers, Havana.

677
695
475
586
549
603
586
528
439
439

402

340
329
457
475
586

1,299

514

7.5

7.7

8.6

8.3

11.8

10.0

10.8

11.6

14.6

17.0

16.7

14.0

19.0

17.0

21.0

15.7

16.3

10.8

7.0

12.2



395

Connecting lake-acreage per mile of river-length between Copperas
Creek dam and Havana at the low gages of 1901 largely exceeded that

in any other section of river above or below, the figure of 1:72.1 acres

per mile being 57 per cent, more than between Chillicothe and the foot

of Peoria Lake and 23 per cent, more than between Havana and the

Lagrange dam—the two other reaches with the highest ratings. (Table,

p. 378.)

Though the eight or nine mile stretch of river just above Havana
has had more shore vegetation at recent summer levels than any other

section below Peoria Lake, the amount of vegetation bordering on chan-

nel of normal width (excluding such areas as Havana Lake) has not

in any recent season been very important. In a local flat stretch of a

quarter mile on the west side above Liverpool, where there was more
shore vegetation both in 1913 and 1914 than anywhere else between the

dam and the head of Havana Lake, the extreme width of the weed strip

was about 35 feet, a little less than 5% of the bank to bank width at

the time (about 750 feet) ; while for most of the distance it was not more
than 15 feet. Nowhere else between Copperas Creek dam and the head
of Havana Lake was there in 1913 or 191-t shore vegetation for any im-

portant distance that occupied more than a ten-foot strip next the bank,

and there were long stretches with much less than that amount. In the

shore zones of the wide water above the mouth of Spoon River there

are several acres of Potamogeton on the west side in the most favorable

seasons ; and on the east side a narrower strip, sometimes up to 50 or 60

feet wide, in a stretch of about 300 yards along the edge of Cook's
Island. Even these local areas, relatively to the vastly greater river

acreages wholly without aquatic vegetation in the 16.8 miles, are extremely
smiall, and revert largely to open water in all but the driest seasons.

Bottom Fatma.—A total of 16 channel collections and 23 collections

in the shore zones (within the 7-foot line) were made in July-October,
1915, between Copperas Creek dam and Havana in cross-section: at

Bottom Coij.ections, Coppeeas Creek Dam to Havana
jui-y-octobee, 1915



39G

Iwo stations in the shallower swifter section of i.8 miles between the

dam and Mile 129 (1 mile above Liverpool) ; and at two stations in the

deeper more stagnant section of 9 miles between Mile 129 and Havana.

Although the entire section of over 16 miles is on the average

richer in small bottom animals than any other sections heretofore

treated, biologically, as well as in its hydrographical characters, it is sep-

arable into two well-distinguished portions, the half with the richer

channel bottom fauna being the deeper muddier section below Mile 129

and more immediately above the high Spoon-River bar. The average of

the poundages per acre at the channel stations in the lower half of the sec-

tion (5,156.0 lbs.) was in fact nearly six times the average valuation of

channel above Mile 129 (878.3 lbs. per acre), and almost fifteen times

the average valuation at the channel stations between Chillicothe and

the foot of Peoria Lake, Peoria Narrows excepted (345.1 lbs.).

Bottom Fauna, 1915, Copperas Ceeek Dam to Havana
POUNDS PER acre (AVEKAGE TOTAL)



397

Bottom Fauna, Channel, 1 Mile above Liverpool to Havana, 1915

Viviparidae
and

Pleuroceridae

Small
Gastropoda

and
Sphaeriidae

Insects,

worms,
Crustacea

Number per sq. yard,
Average 1,294.0 1,468.8

8 coll.'s

Pounds per acre,

Average



398

Bottom Fauna, 4

—

7-ft. Zone, 1 Mile AnovE Liverpool to Havana, 1915



399

3. The 12.0 miles between a point one mile above Beardstown and

the dam at Lagrange, where the slope of water surface in July, 1901, was

only 0.10 inch per mile, but the flood velocity (153.04 feet per second

in March, 1903) greater even than between Havana and Sheldon's

Grove.

Decline in Elevation of Low-Water Surface, 1901; and Flood Velocity



400

both increased velocities and increased flood volumes retard sedimen-

tation and keep the summit of the bar lower than in the other two cases.

Lake and other backwater acreage per mile between Havana and
the Lagrange dam (382.4 acres) exceeded at the low water of 1901 that

of any other reach of river except the 16.8 miles between Copperas
Creek dam and Havana.* The densest distribution of pond acreage oc-

curs in the 9 rniles between the foot of Grand Island and the mouth of

the Sangamon and falls within the boundaries of greatest channel

depths, least flood velocity, softest and darkest-colored bottom deposits,

and richest bottom fauna, as shown by our collections of 1915.

WiiwHS AND Depths, Havana to Lagrange Dam, Low Water, 1901

Miles
above
Grafton



401

Bottom Fauna.—A total of 58 bottom collections, at 9 stations, in

cross-section, were taken in 1915 between Havana and the Lagrange dam,
distributed between the channel and the shore zones and from north to

south as shown in the following table.

Collections, Havana to Lagrange Dam, 1915

Miles
above

Grafton
Channel 4—7-ft. zone 1—3-ft. zone

114.7

113.7

1. Havana to foot Grand Island
(13.8 miles)

Opposite foot Matanzas Lake
500 yards above head of Grand

Island



402

importantly to weights, making up at the best only about 6 pounds of

the total acre valuation.

Bottom Fauna, 1915, Havana to Lagrange Dam
POUNDS PER acre, AVERAGE TOTALS

Reach



4:03

Bottom Faxtna, 1915, 1—3-rooT Zone, Havana to Lagrange Dam (42.5 miles)



404

Bottom Fauna, 1915, 1—3-rooT Zone, Foot op Geand Island to Bbowninq
(9 MILES)



405

in the 31 miles below Kampsville (2.44 inches per mile) was more than

in the short swift stretch between Peoria and Pekin.

A comparatively well-scoured channel bottom is found most of the

way from Lagrange to the mouth, sand, mud and shell, or dirty sand

prevailing, and such mud bottom as occurs being usually hard and
covered at most with only a very thin layer of recent silt. Inside the

7-foot line in 1915 a soft light-colored silt 2 inches to more than 12

inches deep was found at most of our collecting stations. The most im-

portant local stretches of muddy channel in 1915 were 6 miles imme-
diately above the Kampsville dam; and about 4 miles just above the

mouth of the river. A less important short section of muddy channel, in

Widths and Depths, Lageange Dam to Grafton, Low Water, 1901

Miles
above
Grafton



406

the first mile below Six Mile Island—a local section with little drop in

levels at low water—had a deep deposit of light-colored mud in 1913,

but apparently much less two years later.

In the 46 miles between Lagrange and Kampsville extreme depths in

the channel at the low water of 1901 ranged from 9 to 11 feet as a rule,

and did not anywhere exceed 15 feet. Widths at these levels were be-

tween 1,000 and 1,400 feet for good stretches, and did not fall below 800

feet for any important distance. Below the Kampsville dam widths

were seldom' under 800 feet, ranging between 1,000 and 1,200 feet

for most of the way, and reaching a maximum of 1,600 in the sluggish

section just below Six Mile Island.

Connecting lake and other backwater acreage per mile between La-

grange and the mouth of the Illinois at the low levels of 1901 (219.6

acres per mile between Lagrange and Florence; 180.0 between Florence

and Kampsville ; 86.9 between Kampsville and the mouth) compared

unfavorably with that of most of the river between Chillicothe and

Havana.* The greater part of this backwater was leveed and drained

between 1901 and 1913, resulting, no doubt, in recent years in a some-

what better scoured channel even than is indicated by the government

borings made between 1901 and 1905. As in the 42 miles above the

Lagrange dam, shore vegetation between Lagrange and the mouth of

the river has in recent years been a negligible quantity.

Bottom Collections, Lageange to Grafton, 1915

Miles
above

Grafton



407

Bottom Fauna.—In August, 1915, a total of 75 collections of the
bottom animals were made in cross-section at 15 stations between La-
grange dam and the mouth of the river, as shown in the preceding table.

The bottom-fauna valuations indicated between Lagrange and Graf-
ton by our collections of August, 1915, were almost uniformly poor both
in the shore zones and in the channel—the average of the sixteen channel
collections being only 6.7 lbs. per acre; that of .31 collections between
4^7-feet, 16.7 lbs. ; and that of 28 collections within the -l-foot line, 16.9

lbs. The best local figures for the shore were obtained in the l:-7-foot zone
opposite Meredosia, where two hauls averaged 57.5 lbs. per acre ; and
in the 1-3-foot zone below Kampsville dam, where twelve collections

averaged 27.9 lbs. Both in the channel and in the shore zones, if we
except the 4-7-foot zone collections opposite Meredosia, MoUusca con-
tributed less or very little more to the average weight of collections than
did insects, worms, and small Crustacea, which together made up 63 to

65% of the average weight of collections in those depths zones, with
the noted exception. Of the latter group (non-Mollusca) the most im-
portant in weight were the larvae of caddis-flies in the channel, and the
immature stages of Ephemeridae (willow-flies) in the shore zones. As
these were principally of the new broods hatched from eggs deposited
by the adults which emerged only a month to six weeks earlier, they
contributed less to the weight of collections than they would have done
in the same numbers earlier in the summer or later in the fall. The
larger snails (Viviparidae and Pleuroceridae) amounted nowhere be-
low Lagrange to more than 5 or 10% of the weight of collections.

Bottom Fauna, 1915, Lagkange to Grafton
pounds per acke (average total)

Reach



408

Bottom Fauna, Channel, Laghange to Grafton, 1915
POUNDS PER acre



409

Bottom Fauna, 1

—

3-foot Zone, Lagrange to Grafton, 1915
POUNDS PER acre



410

factors clearly influencing—more particularly, of course, in the channel

—

both the depth and softness of the bottom deposits (regarded as a

medium or as a substratum for the bottom population), and also the food

supply of the bottom animals so far as it is brought to them by sedi-

mentation. In the two richer reaches of river above Havana the average

flood velocity in recent years (around 0.9-miles per hour) has been only

about s/i of that between Havana and Lagrange (1.5 miles per hour),

and less than half the average between Lagrange and Grafton (1.9

miles per hour).

Though there is usually, both in the slower and swifter reaches of

the river, if we except the cases of some sharp bends, some retardation

of current between mid-channel and shore, with accompanying increase

in sedimentation and noticeable differences in the composition of the bot-

tom populations, these differences in the less rapid sections above Havana
are neither very important quantitatively nor correlated so far as can be

seen. The average poundages per acre of bottom animals between Chilli-

cothe and Copperas Creek dam in the channel and the shore zones (chan-

nel, 239 lbs.; 4—7-foot zone, 372 lbs.; 1—3-foot zone, 225 lbs.) are in

fact so nearly the same that little if any significance can be attached to

the differences; while in the 16.8 miles between Copperas Creek and

Havana (channel, 3,029 lbs.; 4—7-foot zone, 1,960 lbs.; 1—3-foot zone,

920 lbs.) the differences in weight between the shore and channel stocks

are in the reverse of the direction that might be expected. There is,

however, a decidedly sharper contrast below Havana between the physical

characters of the channel and shore zones, and in and to either side of

the stretch of comparatively hard-bottomed channel between Havana and

Lagrange a corresponding contrast in the richness of the bottom fauna

that is without much question connected with it. In this section of 48.5

miles the 4—7-foot zone (282 lbs. per acre) had stocks thirteen times as

rich as those of the channel (22 lbs.) ; aAd there was a further large in-

crease shown in the stocks in the 1—3-foot zone.

Certain special influences that may affect the bottom-fauna yields

in the river below the Lagrange dam are discussed in a following sec-

tion.

2. ALL-ZONE AVERAGES AND TOTAL STOCKS

All-zone averages of the bottom-fauna stocks of the four main river

reaches below Chillicothe based upon rough acreage-weightings show a

figure for the first 43.7 miles below Chillicothe (264 lbs. per acre) about

the same as the average for the entire 180.5 miles between Chillicothe

and Grafton (261 lbs.) ; for the 16.8 miles between Copperas Creek dam
and Havana about ten times that (3,693 lbs.) ; for the 42.5 miles be-

tween Havana and Lagrange a rate of yield (88 lbs. per acre) about

one third of the general river average and about one thirtieth of the rate

in the richest section; and for the 77.5 miles below Lagrange (10.4 lbs.

per acre) less than one twenty-fifth of the 180 mile average and less



411

Average velocity

miles

per

hour



412

than one two-hundredth of the rate between Copperas Creek dam and

Havana.
Figures for the total stocks present in the combined channel and

shore acreage below Chillicothe July-October 1915 (table, p. 18), based

on these all-zone weight valuations and on approximate acreages for

average Tuly-October levels in 1910—1914, show that out of total stocks

equaling" 6,988,103 pounds for about 26,700 acres, 92.7 per cent., or

6,480,952 pounds, were in the 60.5 mile section of river above Havana

—

this constituting only one third of the total length of river studied and

less than one third of the total river acreage. Again, of the total bottom-

fauna stocks 53.9%, or 3,770,200 pounds, were in the 16.8 miles of river

between Copperas Creek and Havana—which comprises less than one

tenth of the total distance between Chillicothe and the mouth, and only

about one twentieth of the total acreage. The stocks between Havana
and Lagrange, 396,880 lbs., for 42.5 miles, made up but 5.6% of the

grand total; and those between Lagrange and Grafton, 110,271 lbs.,

for 77.5 miles, only 1.5 per cent.

Bottom Fauna, Illinois River, 1915. Acreage-weighted All-Zone Averages

pounds per acre

Reach



413

43 Q

s ^

111



414

weight running in these reaches from 86 to over 99%, and falling below
90% only in the 1—3-foot zone above the Copperas Creek dam. Below
the Lagrange dam, where the large Ephemeridae (May-flies) were rela-

tively much more abundant than farther north, the MoUusca percentages
dropper to an average range between 35 and G87r-

In the sections above Lagrange, if we except the 4—7-foot zone
between Copperas Creek dam and Havana, the larger snails (Viviparidae
and Pleuroceridae) accounted for 70 to nearly 100% of the Mollusca
totals (by weight). Below Lagrange the Viviparidae (and Pleuroceri-

dae) were largely replaced by Sphaeriidae in all zones, the weight per-

centages of that group rising to a range between 84 and 100%..

Bottom Fauna, Illinois River, 1915

Percentages op Average Total Valuations by Weight
contributed bt mollusca



415

1



416

a fe

si



417

*; ce



418

The Bottom Fauna of the Lakes and Ponds of the Illinois River
Bottom-lands between Copperas Creek Dam and

Lagrange, July—October, 1914—1915

1. Hydrography and Physical Features

In the midsummer and autumn months of 1914 and 1915 a total

of 266 bottom collections, principally with the mud-dipper, were made in

the lakes and ponds and other backwaters in the river bottoms between
the head of Clear Lake and the foot of Sangamon Bay, covering a river

distance of 39 miles, and representing an ex-river acreage (about 16.000

acres) at a gage of 8 feet, Havana, around one third of the total prevailing

at the time between the Copperas Creek and Lagrange dams (about 52,000

acres).

The lakes and backwaters studied, separate naturally on a basis of

physical and hydrographical features into five classes

:

I. The deeper lakes of the all-bottom-land type, with fiat muddy
banks on both sides, and with maximum depths at recent midsummer
levels between TJX and 9 feet. The five lakes of this class examined

—

Clear—Mud, Liverpool, Thompson, Dogfish, and Sangamon Bay—have
deep soft black mud bottom in the central deeper portions, and only

rarely a little sand near shore. The vegetation, principally Potamogeto'n
and Ceratophyllum, is confined to the rather wide shallow margins, the

most of it well within the zone of —6 feet. These lakes ranged in size

at the low water of 1901 (4.2 ft., Havana) from 275 to about 1,800 acres,

and represented in all at that gage about 3,390 acres. At the average
gage of July—October, 1910—1914 (approximately 8 ft., Havana), their

acreage is somewhere near 2J/2 times the 1901 figures, or over 8,000

acres, which is close to one seventh of the total lake acreage between
Copperas Creek dam and Lagrange, and more than the total river acreage
at the same gage in the same distance (about 6,000 acres).

n. The deeper, sand-beach type, bordering on one side against the

sandy bluff, and with sandy shore on that side, but with flat muddy banks
opposite. The two lakes of this type studied (Quiver and Matanzas)
had a total acreage at the low water of 1901 of more than 600 acres), and
maximum depths at recent midsummer levels of 8J4 to 12 feet. In

Quiver Lake there is some sand and large quantities of old shells mixed
with the mud in the deep "channel" which is kept open by the water from
Quiver Creek during freshets. In Matanzas Lake the central open por-

tion has all a soft black mud bottom. The vegetation in these two lakes

is in its character and in its distribution not essentially different from
that of the lakes of Class I, though it is inclined to be rather less dense

on the average. These lakes receive a comparatively large amount of

spring water from the sandy bluff on the east side, and their waters
average somewhat clearer and (except at times of invasion by river

water) poorer in plankton than the lakes of the all-bottom-land type.



419

III. The comparatively shallow, weedy lakes, with maximum
depths at gage 8 feet, Havana, of about 5 feet. The lakes of this class

in which collections were made in 1914 and 1915 (Flag, Seebs, Stewart)
represented a total acreage at the low water of 1901 of about 1,500 acres,

and at 8 feet, Havana, somewhere near 1,000. All of these lakes went
completely dry in seasons of extreme low water before 1900. Both in

the shallower and the deeper portions the black bottom deposits con-
tain a much larger percentage of partially decayed dead vegetation than
is found in the open waters of the lakes of Class I. In recent midsummer
seasons, up to 1911, Flag and Seebs lakes have been almost completely
filled with growing vegetation. In Stewart Lake at the same time some
open water was to be found in the central deeper portion toward the

foot, but much less relatively to the total area than was the case in such
lakes as Thompson and other deeper lakes of its type.

IV. The very shallow, very weedy lakes, with greatest depths at

the low water of 1910—1911 between Syi and 4 feet. These lakes
(Duck, Dennis, Crane) were little more than lily or flag ponds before
1900, going wholly dry at low water in most seasons before the opening
of the Chicago Sanitary Canal. Between August and October, 1914,
Duck and Dennis lakes were so filled with mixed .vegetation that it was
difficult to pass through them with a skiff, even the fallen dead stems
of the coarse water-plants being blanketed with living filamentous
algae. Crane Lake in 1914 and other recent years has been a vast lily-

bed, with its rather more open, but densely shaded bottom sprinkled
with dead lily stems and "yorkey-nuts". These three lakes had a low-
water acreage in 1901 around 1,200 acres.

V. The shallow dead timber and brush areas first permanently
submerged after the opening of the Sanitary Canal in January, 1900.
These shallow backwaters, ranging in depth from IJX to 4 feet over
most of their areas, have alternating opener and densely weeded
stretches, the prevailing vegetation being Potamogetom and Polygonum.
Their location on the ridges between such lakes as Flag and Thompson,
and on similar ridges between these lakes and others and the river,

makes them in reality littoral, either of the river or of lakes of the pre-
ceding classes, as the case may be. Their bottom soil still contains
abundant traces of the sticks and dead leaves contributed by the willows
and mallows and button-bushes that grew there 20 years ago. The area
represented by waters of this type can only, for the present, be roughly
estimated. The total area under 4 feet in depth at the July-October levels

of recent years between Copperas Creek and Lagrange dams (about 29,700
acres) made up over 50% of the total ex-river acreage, while careful
estimates in the case of Thompson Lake as flooded to the same elevation
(approx. Havana 8 ft.) indicated that on that gage in this lake these areas
made up about 30% of the total land flooded. The dead timber and brush
areas studied by us in 1914 and 1915 were all in the vicinity of Havana
and were variously contiguous with Clear, Flag, Thompson, Dogfish,
and Quiver lakes.



420

2. Bottom Fauna of the Lakes, by Classes

Class I.—Fiftj'-three collections from open water over 6 feet in

depth in the deeper all-bottom-land lakes of Class I in 1914 and 1915

averaged 222 pounds per acre of bottom animals, after deducting shells

of MoUusca. An average about twice as great (441 lbs.) was shown by
78 collections from the 1—6-foot zone, 21 of these hauls coming from
open bottom and having an average of 696 lbs. per acre, and 57 from
more or less weedy bottom, with an average of 347 lbs. The average

of the total of 131 collections from the five lakes, all depths, in both

seasons, was 352 pounds. Forty-two of the total 131 collections were
taken in 1914 and 89 in 1915.

Thompson Lake, both in 1914 and 1915, easily outranked the other

lakes of its class studied in the richness of its bottom fauna, its average

of over 540 lbs. per acre, in either season, being more than double the

best other lake average in this class, (Dogfish,) and nearly three times

the lowest (Liverpool).

Class II.—-The two sand-beach lakes (Quiver and Matanzas)
showed a combined average for 1914 and 1915, for open water over 6

feet, of 1,667 lbs. per acre, for a total of 27 collections. Of these, 18

were from Quiver Lake, with an average of 2,471 lbs., and 9 from
Matanzas Lake, with an average of only 58 lbs. per acre. The combined
average of 37 collections, from the 1—6-foot vegetation zone, was 351 lbs.,

the average of Matanzas again being lower than that of Quiver. The
general average, for the total of 64 collections, both lakes, both years,

and all depths, was 848 lbs. per acre, or more than twice that of the

lakes of Class L It will be noted, however, that the very high average

for this class and for Quiver alone, was largely due to a few enormous
hauls of large Viviparidae in the deep "channel" in 1914. These were
much reduced in numbers and weight per acre in 1915.

Classes III, IV, V.—The shallow weedy lakes of Class IH, Flag,

Seebs, and Stewart, averaged only 57 lbs. per acre, combined average of

45 collections, all depths, both seasons ; and the very shallow, very weedy
lakes (Duck—Dennis, Crane) only 94 lbs. per acre for a total of 10

collections. As will be shown in the next section, however, it was in

these shallower, weedier lakes, and in other weedy backwaters, that the

shore animals in the weeds (above the bottom) reach their highest

figures. In the dead timber and brush areas the bottom-fauna average

of 16 collections, 1914—1915 (187 lbs.) was better than in weedy lakes

of Classes III and IV, approaching, in fact, the average of the open
water of the deep lakes of the all-bottom-land type (322 lbs.).



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425

3. General Average Valuation

A simple average (without weighting to compensate for irregularity

in distribution of collections within different lake classes) of the total

of 26G bottom collections of I'tl-t—1915 from the five classes of lakes

and backwaters (including dead timber and brush areas) figures out

at 402 lbs. per acre. Since the general average of 848 lbs. per acre for

the Class II lakes (Quiver, etc.) applied to but 630 acres at the low
water of IDOl, while the average of 3.52 lbs. per acre for the Class I

lakes covered 3,3!JO acres at the same gage, it is evident that a simple

average of this sort is unfair and likely to be unduly high. As we have
not complete acreage figures for different depths at recent gages pre-

vailing in midsummer, and lack, in particular, exact figures on the dead
timber acreage, a close general average of all the lakes and backwaters
studied in the two years, based on accurate acreage weightings, can not

now be figured. If we assume, however, that on the average the ex-

pansion in lake acreage between 4.2 and 8 feet, Havana, is about the

same in all of the first four classes of lakes except Class II, we shall

not go far wrong in weighting the class average of I to IV, excluding

the dead timber and brush areas, with the low-water acreage for 1901.

The general bottom-faima average for Classes I—IV, inclusive, figures

out in this way at 2S^ lbs. per acre. If, again, we assume that the usual

ratio of adjacent dead-timber acreage to the total acreage of lakes and
backwaters at gage 8 feet, Havana, is about the same as in Thompson
Lake (around 30%, estimated), and weight the Class I—IV average

(285 lbs.) and the Class V average (187 lbs., dead timber and brush

areas) with "per cent." acreage figures on this basis, we obtain a gen-

eral average of bottom fauna for the two years, for all classes of lakes

and backwaters, all depths, of 2§§ lbs. per acre, or almost exactly the

general river average for 180.5 miles below Chillicothe (261 lbs.), but

only about one third of the all-zone river average for the 59.3 miles be-

tween Copperas Creek and Lagrange dams (705 lbs.).



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427

i. Composition of the Bottom Fauna

The proportion of ^Mollusca to associated animals in the lake col-

lections of lUl-1—1913 did not run so uniformly high as in the river

series of 1915. The MoUusca percentages are highest in the open water

of the deeper lakes of Classes I and II, where they run from 84 to 96%.
In the weedy zones (1—6 feet) of the deeper lakes the Mollusca per-

centages were noticeably lower (7?%). In the shallower weedy lakes

of Classes III and IV the insects and small Crustacea are much more
abundant relatively, and the Mollusca ratios drop to 36 and 50%.

Per Cent. Mollusca by Weight (to Total Weight of Collections),

Lakes, 1914—1915

Zone over
6 feet

open water

1—6 ft.,

no vegetation
1—6 ft.,

vegetation

Class I

Class II

Class III

Class IV
Class V

84.1

96.8

77.8

77.5

50.7

36,4

79.7

The snail fauna of the lakes, like the insect fauna, presents in the

average somewhat greater variety than that of the river. \'iviparidae

made up the largest percentage of the Mollusca totals in the deeper lakes

of Classes I and II. In the shallower weedy lakes and in the dead timber

areas the ratios of Viviparidae were lower. The smaller snail fauna

(smaller Gastropoda, Sphaeriidae) less rarely than in the river consisted

almost exclusively of Sphaeriidae—the \'alvatidae and Amnicolidae
being well 'represented in most of the lakes studied, and exceeding

Sphaeriidae in some cases, in the shallower weedier lakes, both in num-
bers and weight.

Further details of the composition of the lake bottom-fauna are

shown in the detail tables at the end.

Pep. Cent, of VniPAniDAE, by Weight, to Tot^u. Weight of all Mollusca,

Lakes, 1914—1915

Zone over
6 ft.

open water

1—6 ft.,

no vegetation

Class I

Class II

Class III

Class IV
Class V

56%
99%

85%

1—6 ft.,

vegetation

86%
88%
62%
61%
77%



428

Illinois Valley Lakes, 1914—1915, Bottom Fauna
pounds per acre

I. Deep Bottom-land Type. (Zone over 6 feet)

Lake



429

I. Deep Bottomland Type. (1—6-ft. Zone. Vegetation)

Clear—Mud, 1915



430

Illinois Valley Lakes, 1914—1915, Bottom Fauna
pounds pek acke

III. Shallow, tVeedy Type. (Depth 1—5 ft.)

Lake



431

The Weed-Fauna of the 1—4-foot Zone of the Illinois Valley

Lakes, and the Combined Bottom- and Weed-Fauna
Average, August—October, 1914

1. Weed Fauna of the Lakes near Havana-

In the autumn of 1914 a series of quantitative collections of the

small invertebrates attached to and scattered between the leaves and
stems of the denser growths of coarse vegetation about the margins of

the bottom-land lakes near Havana, in depths 1 to -iyi feet, were made
at seven stations. These collections were made by inclosing the tops of

the plants in a large bucket, lowered about them to a depth of about 9

inches, cutting off the stems a little below the !>-inch le\el, shaking them
out thoroughly in the water obtained by righting the bucket, and then

passing the water saved through a fine sieve. Though these collections

represent but a fraction of the total "weed fauna", omitting the small

insects and other animals occurring between the bottom and the lower
limit of the bucket hauls (a distance of 1 to 3 feet), the average valua-

tions obtained in this way were very much above the average bottom
valuations from the same lakes in any zone, with the single exception

of a few hauls from the bottom of the Quiver Lake "channel" in 1914.

The general average for the seven stations was in fact 2,118 lbs. per

acre, or more than eight times the general average of bottom fauna for

the five classes of lakes and backwaters between the head-of Clear Lake
and Beardstown studied by us in 1914 and 1915 (355 lbs.).

The smaller snails (Amnicolidae, Physidae, and Valvatidae, prin-

cipally) formed about 50% of the average total by weight. The ap-
proximate half of the collections made up of insects ( larvae and nymphs)
consisted principally of immature Odonata (Agrionidae and small Libel-

lulidae). The only large snails were a few adult Planorbis trk'ohns,

the great bulk of the material being of quite small size and easily avail-

able, in that respect, for use as food by young to half-grown as well as

adult fishes.

3. Combined Average Valuation of the Bottom- and Weed-Fauna
Stocks, and Total Stocks in the Acreage

For the purpose of calculating a general average, and also the total

stocks, both of the bottom and weed animals, for the entire lake and
other backwater acreage between Copperas Creek dam and Lagrange
(approximately 52,700 acres at 8 feet, Havana—the average gage in

July—October, 1910—1914), I have assigned the general bottom-fauna
average of the twelve lakes studied (355 lbs.) to the entire acreage, as

with no levees, and the weed-fauna average of the lakes in the imme-
diate neighborhood of Havana (2,118 lbs.) to the approximate 29.700
acres with depths under 4 feet in the district. An acreage-weighted
general average figured in this way stands at 1,447 lbs. per acre, or at



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more than twice the all-zone river average for bottom fauna only in the

same distance (TOS lbs.), and at more than SJ/ times the average

figures for bottom fauna only in the lakes and other backwaters be-

tween the two dams in 1914 and 1915 (255 lbs.)-

The total stocks in the entire 52,7'60 acres of lakes and ponds

(acreage as with no levees, substantially same as 1908 rather than

1914—1915, for purpose of comparison with fish yields of that year),

76,358,400 lbs. is more than 10 times the total stocks in the 59.3 miles

of river opposite (6,988,103 lbs. for 36,700 acres). Of the total, 13,-

453,800 lbs., or 17.6%, represents the bottom animals of the full acreage;

and 62,904,600 lbs., or 82.3%, represents the small weed animals of the

upper 9 inches only, in the rather more than 50% of the total acreage

within the 4- foot line.

Bottom- and Weed-Fauna Stocks, Lakes, Copperas Creek Dam to

Lagrange (59.3 miles)



434

scanty vegetation, or none at all, lying between the weedy shore zone

and the deep open water, part of it sometimes extending within the 7-

foot line.

Valuations considerably better than the average were obtained in

restricted areas with more nearly uniform bottom in four of the isolated

lakes, the average for clay bottom overlaid with fine decayed vegetation,

in Deep Lake being 320 lbs. ; for sand and clay, in Cedar Lake, 251 lbs.

;

for gravel and sand, in Deep Lake, 220 lbs. ; and for gravel and sand,

in Lake Zurich, 213 lbs.

In its composition the littoral bottom-fauna of these lakes differs

most strikingly from that of the Illinois Valley bottom-land lakes in the

relatively much lower percentages of Mollusca. Snails made up only

Lakes, Northeasteen Illinois, August—October, 1916, Bottom Fauna
pounds per acre

Littoral Zone, 1—7 feet. Some Vegetation

Lake



435

17.4% of the average weight of the hauls at 66 stations in the six iso-

lated lakes; and only 41.8% in the two lakes traversed by the Fox River

channel. The snails belonged almost entirely to the smaller-sized

species, the larger Pleurocendae and Viviparidae occurring only very

rarely and in small numbers in the hauls. The most abundant families

were the Sphaeriidae, Amnicolidae, Valvatidae, and Physidae. The most

important insects, measured by weight, were the Trichoptera (caddis-

flies j, Chironomidae, and large Ephemeridae (May-flies).

(A more complete report on these collections, including also the

dredgings in deep water, is being planned for publication later.)

2. Weed Fauna

In August, 1916, we found the shore vegetation of the isolated glacial

lakes so generally thin and sparse, as compared with the dense growths

of Potamogeton and Ceratophyllum in the Illinois River bottom-land

lakes, that it was practically impossible to employ the bucket method of

collecting the weed animals used at Havana in 1914. Along the north

shores of Pistakee and Nippersink lakes, however, beds of mixed
Potamogeton, Myriophyllum, and Ceratophyllum were not uncommon
that were fully as dense and that carried not far from as rich a fauna

as that of such lakes as Flag and Thompson. The average for the upper

9 inches at two stations in Pistakee and Nippersink lakes in August, 1916

(1,665 lbs. per acre), was only 26% less than the average of the seven

weed-fauna stations in the vicinity of Havana in 1914 (2,118 lbs.). Both
insects and moUusks constituted an almost insignificant part of the

totals, 85% of the weight in one case, and 95% in the other being made
up of a single small crustacean—the little fresh-water shrimp, Hyalclla

kiiickcrbockcri. (Table, p. 436.)

Comparison with Outside Bottom- and
Weed-Fauna Valuations

1. Bottom- and Weed-Fauna of Oneida Lake. (Baker, 1918)

In the Lower South Bay of Oneida Lake, New York, in 1916, Baker
found the richest bottom-fauna within the 6-foot contour. Averaged

by weight*, in pounds per acre, sand bottom showed the highest valua-

tions, 143 sixteen square-inch units examined, averaging 387 lbs. Gravel

bottom, with 207 lbs., clay bottom, with 188 lbs., and sand and clay,

with 210 lbs., were well under sand bottom in richness, but were all much
richer than the mud bottom over 6 feet. The mud bottom within the fi-

foot line averaged for 27 units 230 lbs. per acre. These valuations much

* Rough, approximate valuations, by present author, from Baker's figures
per unit of 16 square inches, on same general basis followed in valuation of Illinois
River and lake data, 1914—1916. Average adult size of some of the snails esti-

mated by Mr. Baker. Chironomidae and larvae of Trichoptera lumped and aver-
aged at a round valuation about the average of those of northeastern Illinois
glacial lakes.



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exceed the average figures obtained by us in 1916 in the same depth

zone in the isolated glacial lakes of northern Illinois (105 lbs.), but do
not average much if any better than the best littoral areas in Deep and
Cedar lakes ( Deep Lake, gravel bottom. 220 lbs., clay and rotten vegeta-

tion, 320 lbs.; Cedar Lake, sand and clay bottom, 231 lbs.). They com-
pare very well with the all-depth average (one to eleven feet) for the

Illinois Valley lakes of all classes in 1914 and 1915 (255 lbs. per acre),

but are exceeded by the general average of bottom fauna only in the 1—6-

foot zone of our Class I lakes in the Havana district (441 lbs.) ; and are

far surpassed by the figures for the 1—3- and 4—T-foot zones of the

Illinois River between Copperas Creek dam and Havana (1—3-foot

zone, 919 lbs.; 4—?-foot zone, 1,960 lbs.). The ratio of Mollusca to the

total weight of all animals averaged much higher (38^ to 64%) than
in the glacial lakes of northern Illinois, but was far under the ratios

found in the Illinois River and in the lakes near Havana.

Bottom Fauna of Oneida Lake, 1

—

6-foot Zone

pounds peb acre (oue valuations)



438

2. Bottom Fauna of Lake Mendota. (Muttkowski, 1918)

Average valuations in pounds per acre for the —1- and 1—3-meter

zones obtained by Muttkowski in Lake Mendota in 1914 and 1915 (60

and 64 lbs. respectively) are slightly higher than our averages of 1916

from the 1—6-foot zone of Fox and Pistakee lakes (54 lbs.), but are

well under the average for the six isolated glacial lakes (105 lbs.).

Mollusca formed only 4% of the total average weight in the —l-rrieter

areas, and 14% in the 1—3-meter zone. The most important groups of

animals as measured by weight were the larvae of Chironomidae and

Trichoptera.

Bottom fauna of Lake Mendota, Wisconsin. 1—3 meters
pounds per acre (our valuations)



439

Copperas Creek dam and Havana; The Mytilus taken by Petersen, as

shown by the photographed heaps as they fell out of the bottom sampler,

were lying upon each other on the sea bottom.

Marine Bottom Fauna Valuations (Pettebsen, 1911—1918)

averages, pounds per acre*, large areas



440

plankton also. The specimens that fall clearly into the group of plankton-

feeders represented a rather wide range of families, including Sphaeriidae
(as represented by Sphaerium striatinum)

;
young Unionidae, about one

year old; Bryozoa (Urnatella gracilis) ; Trichoptera (larvae of Hydrop-
syche species); Chironomidae (unidentified red larvae); and Planaria.

The stomachs of the Sphaeriidae and young Unionidae, though con-
taining principally settled limnetic plankton, held also small amounts of

fine dead detritus, as well as many living bacteria, apparently taken in

with the latter or with dead planktonts. The insect larvae (caddis and
Chironomidae) had enjoyed a clean feed of settled plankton, some of it

still alive when eaten. Some living bacteria were seen in the stomachs
of the caddis larvae. Species whose stomachs contained nothing but
dead detritus included a small Asellus and several tubificid worms. The
larger snails of the family Viviparidae (Cauipcloina snbsolidmn and
Vivipara contectoidcs) had eaten large quantities of loose detritus and
what appeared to be slime-clotted silt and organic detritus particles such
as is commonly found as a thin coating on the shells of the snails them-
selves and on other hard objects in the mud. Living bacteria, presumably
putrefactive or fermentative types, were exceedingly abundant in the ma-
terial in their stomachs. In small specimens of Vivipara and Campeloma,
on the other hand, diatoms and Chlorophyceae from the settling limnetic

plankton were not much if any less abundant than old dead detritus. At-
tached incrusting algae (Pleurococcus and Palmella types) were present

in the stomachs of all Viviparidae examined.

In going through samples of the loose bottom-ooze taken with the

mud-sucker (see Figure 6, page 372), I was struck with the fact that

limnetic plankton, principally diatoms and Chlorophyceae, was, next after

the flaky particles of decayed vegetable or animal matter that makes up
the dead organic detritus, the most abundant edible element in the ooze,

as far as could be determined, being decidedly more important in bulk

than normal bottom Protozoa and Rotifera. While bottom Ostracoda

were noted in the ooze they were relatively very rare, and limnetic

Copepoda, Cladocera, and Rotifera were represented only by fragments

or nearly whole carapaces or other chitinous parts.

The enormous numbers of bacteria seen swarming in and among
the flaky honeycombed particles of dead organic matter, and inside the

bodies of recently dead planktonts, suggest that these minute organisms

are themselves not an unimportant part of the food supply of both the

plankton- and detritus-eating bottom-animals. Both bacteria and minute

pale flagellates and ciliates were also very abundant in the interstices of

the slimfe-bound silt and detritus scum that envelops the upper surface of

the shells of a large portion of the living and dead snails. That this ma-
terial on their own backs is used as food by their fellows is apparently

proven by its presence in the stomachs as well as by the numerous
tracks of radulae identified in the mantle of scum on the backs of liv-

ing Vivipara and Campeloma examined.



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•144

The Nitrogen, Org-anic Carbon, and other Oxidizable Matter
in the Bottom Muds of the River and Lakes below

ChilUcothe, 1913—1914

1. Bottom Muds of the Illinois River Channel, 1913

Mud samples taken in the Illinois River channel between Chillicothe

and Kampsville in March and July—October, 1913, showed a rather wide
variation in the amounts of nitrogen present, as expressed in terms of

percentage of dry matter, but both in early spring and late summer
agreed in showing a higher average above than below Havana. In

percentage figures, as stated, five samples from above Havana, all

months taken together, averaged 0.30G% nitrogen, or 61% richer than

the five samples taken on approximately the same dates at stations be-

low Havana, which averaged 0.189%. A lesser actual diiTerence in

average nitrogen content is shown for the stations above and below Ha-
vana, when we take into account the specific gravity and the moisture

percentages of the samples and calculate average values of nitrogen by
weight for a given area to a depth (3 inches) supposed to approximate

the average depth of cut into the soft bottom by the dipper in taking

the samples. The average number of pounds of nitrogen to the acre,

figured in this way, was 1,918 for the stations above Havana; and only

36% less, or 1,417 lbs. per acre for the stations between Lagrange dam
and Kampsville, in which the specific gravity was visibly higher and the

moisture-content lower.

The organic carbon per acre figures out, both above and below Ha-
vana, at about 8 times the nitrogen, the averages standing at 14,111 lbs.

per acre for the stations above and 11,323 lbs. for the stations below
Havana. The total oxidizable matter (which includes both the nitrogen

and the organic carbon, as well as various other substances, some of

them of a mineral nature), figured in the same way, averaged 48,345 lbs.

per acre to a depth of 3 inches in the river channel above Havana, and
31,869 lbs. per acre below Havana.

Compared with the stocks of nitrogen and total oxidizable matter

(dry weight) in the muds either above or below Havana, the total acre-

poundages of dry matter or nitrogen represented by the bottom inverte-

brate population of July—October, 1913, are extremely small, however
liberally figured. Taking the average bottom-fauna stocks of the river

between Chillicothe and Havana (the richest section) as 555 lbs. per
acre (see table, page 412), and assuming a dry-matter content of

about 10% and a percentage of nitrogen to dry matter of 7%, the dry
weight of the average stock of bottom fauna on one acre would stand

at 55 pounds, or about 1/900 of the dry weight of the total oxidizable

matter per acre in the channel mud of that reach, and the contained
nitrogen at less than 4 pounds, or about 1/500 of the total nitrogen per

acre.



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2. Bottom Muds of the Lakes between Copperas Creek Dam
AND BeaRDSTOWN

Comparison of samples from the central portions of eleven lakes be-

tween the head of Clear Lake and Browning, May—October, 1914, on
the dry-weight percentage basis shows the shallow weedy lakes highest

in bottom nitrogen. The average of Flag, Seebs, and Stewart lakes

(Class III lakes) in terms of percentage of dry matter, was 0.39%, com-
pared with an average of 0.27% for seven of the deeper, more open lakes

of Classes I and II; and with 0.26% for Crane Lake—a lake of the very

shallow, very weedy type. The general average of all of the 19 mid-lake
samples from eleven lakes of 4 of the five classes (0.32%) was some-
what more than the average for the river channel stations above Havana
(0.306%) and nearly twice the river average below Havana (0.189%).
The general average of organic carbon in mid-lake samples was 3.89%,
comparing with 2.41% for the river channel above Havana, and with
1.51% for the channel below Havana. In organic carbon as in nitrogen,

the shallow weedy lakes of Classes HI and IV (with 4.30% and 5.19%)
averaged well above the deeper lakes of Classes I and II (with 3.67%
and 3.09%).

Both in Thompson and Quiver lakes, May—October 1914, the ni-

trogen and organic carbon figures were considerably highest in samples
from the shallower water, the percentages of average difference as be-

tween samples from under and over 6 feet in depth amounting in the

case of the nitrogen to over 30%, in both Thompson and Quiver lakes,

and in the case of the organic carbon to 15% in Thompson and to 52%
in Quiver.

Nitrogen and Obganic Cabbon in Muds, Thompson and Quiver Lakes,

May—October, 1914



447

Nitrogen, etc., in Mud of Illinois Valley Lakes, Mat—October, 1914

samples pkom middle, in deepest water
PEB cent, in TEatMS OF DRY MATTER



448

Nitrogen, etc., in Bottom Muds, 1913—1914,

Illinois Riveb Channel and Lakes in Vicinity or Havana



449

the average ratios found by Kofoid* to hold between silk-net and filter-

paper volumes in 1896—1899, show a figure for the twelve-month period

(200,477 tons) almost exactly treble the amount (67,750 tons) that was

carried in the average year just prior to 1900. Of the twelve months'

total about 89 per cent. (179,916 tons) was accounted for during the

four months of the spring season, March to June inclusive, during which

period 1.474 tons passed every twenty-four hours. The 14,025 tons that

passed during the five months July to November inclusive, made up only

6.9 per cent, of the total for the year, but this amounted to ninety-one

tons every twenty-four hours, and was enough if all settled to the bot-

tom to supply 1,698 pounds per acre for every acre in the river below

Copperas Creek dam at the average gage of that season and year (7.8

ft., Havana). The December—February plankton (6,536 tons) was less

than half that of July—Xovember, and only 3.2 per cent, of the total.

The full twelve months' total, over 400,000,000 pounds, amounted to

24,279 pounds per acre for each acre of the approximate acreage in the

river below Copperas Creek dam at recent under-bank-full stages (8 ft.,

Havana) ; or to nearly a hundred times the wet weight of the total

bottom-fauna stocks of July—October, 1915, shells deducted, between

Copperas Creek and Grafton (4,277,351 poimds). The dr\- weight of

this plankton at two to five per cent. (8.000,000 to 20,000,000 pounds)

was twenty to fifty times the estimated dry weight (at 10 per cent.) of

the total bottom stocks of 1915 below Copperas Creek (427,735 pounds).

Complete figures for the plankton stocks produced in the full 120

miles between Havana and Grafton would doubtless also include, in ad-

dition to the Havana figures, new stocks of no small size added on the

way down stream, Ijoth as a result of normal multiplication and lake and

other backwater contribution. I do not take the fact that all of our

down-stream plankton series between 1899 and 1910 showed a large de-

crease in volumes southward of Havana as ruling out the inference of

continued though hidden increase, at a rate merely slower than the rate

of decrease due to consumption and settling. The average time of pas-

-sage between Havana and Grafton was 6.7 days at the average gage of

Jujy—November, 1909 (7.81 ft., Havana), and was 4.82 days at the

average gage of March—June (Havana, 12.04 ft.). During upward
pulses, rates of increase in plankton volumes (c.c. per m^) were several

times recorded both by Kofoid and the writer for the river channel at

Havana and for Thompson Lake, both in spring and autumn months,

1896—1910, that amounted to over 25 per cent, in one day : while in ex-

treme cases the increases ran to 60 to 70 per cent, in a single day, or

400 to 500 per cent, in a week.

Bui. 111. state Lab. Nat. Hist,, Vol. VI.. Art. II., 1903, pp. 552-554.



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451

2. Stocks of Total Nitrogen and Nitrates in the River Channel
AT Chillicothe. 1914—1915

Comparison of the plankton figures obtained at Havana September,

1909—August, 1910, with the total nitrogen and nitrate figures for

Chilhcothe, March, 191-1—February, 1915, does not suggest that plank-

ton production in the river between Havana and Peoria has been at all

in danger of limitation by the nitrogen supply at any season during re-

cent years. The total nitrogen that passed Chillicothe in the twelve

months (67,722 tons) was sufficient, if all metabolized without loss, to

produce more than ninety times the actual stocks of plankton that

passed Havana in the year 1909—1910 (based on a dry-matter per cent.

= 5 ; nitrogen per cent, in dry matter ^ 7) ; while the stock of unused
nitrogen in the form of nitrates (22,345 tons) was capable of producing

under the same conditions more than twenty times the total plankton

that actually passed Havana in 1909—1910. At the dry matter and ni-

trogen ratios assumed, only about 1,431,983 pounds out of the total

of 35,444,859 pounds of nitrogen that passed Chillicothe in the year
1914—1915 would be accounted for as nitrogen in the form of living

matter in 400,000,000 pounds of plankton (the approximate amount that

passed Havana September, 1909—August, 1910).

If we could distribute the total nitrogen that passed Chillicothe

over a river acreage of 26,782 acres (the estimated acreage below Chilli-

cothe at about 8 ft., Havana, the average gage of July—November, 1910
—1914), we would have 2,442 pounds per acre in the March—June pe-

riod; 1,495 pounds per acre July—November; 1,119 pounds per acre De-
cember—February ; and a total of 5,057 pounds per acre for the year.

The nitrates, similarly distributed with correspondingly lesser poundages
for the separate seasons, would amount to 1,668 pounds per acre for the

twelve months on the same acreage.

The Peoria discharge data entering into the various tables following

are the rating-table figures of Jacob A. Harman, as published in the

special Report of the Illinois State Board of Health on Sanitary In-

vestigations of the Illinois River, 1901, and more recently used by Alvord
and Burdick in the Report of the Rivers and Lakes Commission on the

Illinois River and its Bottom-lands, 1915. These figures are consider-

ably higher than recent figures of the U. S. Geological Survey, which we
did not have at hand, except in fragmentary form, when the manu-
script for the present article was being prepared.



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455

3. Total Stocks of Oxidizable Matter in the River at
Chillicothe, 1914—1915

Not only the plankton, bul in addition all the other oxidizable matter

carried in the stream-flow, whether suspended or dissolved, may be re-

garded as potential detritus or as potential microorganisms, some portion

of which, in some form 'or other, may be useful as food to .the bottom
animals or to the organisms on which they themselves feed somewhere in

the course of the stream below the sampling point. If the total oxidiza-

ble matter at Chillicothe 1909—1914 was in about the same ratio to the

total nitrogen as in 1900—1902 (about ten times total nitrogen in the

winter and spring months, and seven to nine times the nitrogen figures

in midsummer and autumn), we would have had passing Chillicothe in

the entire year, March, 1914, to February 1915 a total of 617,137 tons, or

over 1,200,000,000 pounds total oxidizable matter, dry weight, or some
sixty to a hundred and fifty times the total dry weight of the plankton
that passed Havana in the twelve months September, 1909, to August,
1910 (eight million to twenty million pounds). If this enormous total

load could be settled out and apportioned equally to the approximate
26,780 acres of river between Chillicothe and Grafton at gage 8 ft., Ha-
vana, each acre would receive in the course of the year 46,086 pounds,
an average equal to more than seventeen hundred times the average dry
weight poundage (about 10 per cent.) of bottom animals per acre

(twenty-six pounds) found in the summer of 1915 between Chillicothe

and the river's mouth. The employment of vertical instead of surface
chemical samples for the determination of loss on ignition would with
little question, also, show still higher values of total oxidizable matter
than those here figured, particularly in seasons of recession from flood,

when the dead suspended organic matter increases heavily in concentra-
tion from the surface downward. (See table on p. 456.)

4. The Portion of the Plankton Settled out or Consumed

Basing the computations on percentage decreases in silk-plankton vol-

umes (c.c. per m.^) between Havana and Grafton in June and August
1910, and on rates of increase in discharge between Havana and the

mouth of the river in the spring and midsummer months, but taking no
account of normal multiplication, there is found for the nine-months

growing season, March—November, 1909—1910, a total loss of plank-

ton in the 120 miles below Havana of 243.503.139 lbs., or almost exactly

two thirds of the total stocks that passed Havana during the period

(387,883,000 lbs.). The dry weight of this lost plankton at 5% (12,-

175,156 lbs.) amounts to nearly 30 times the dry weight, estimated at

10%, of the bottom animals found in 1915 in approximately the same
reach of river in which the loss occurred (total bottom-fauna stocks

Copperas dam—Grafton, 1915, 4,277,350 lbs ; dry weight at 10%, 427,-

735 lbs.).



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457

That the greater part of the plankton lost, or all of it, was settled

out or consumed by larger organisms, rather than that it perished be-

cause of any failure of the food supply (particularly nitrogen), is forci-

bly suggested by two or three considerations : that the losses took place

at the greatest rate during the hot season, when the current was least and
settling easiest, the rate of loss in August 1910 being i)8%; and that in-

stead of there appearing any evidence that the losses were due to dim-
inution in food, both the total limnetic nitrogen and the nitrogen in the

form of nitrates increased down-stream both in the spring and midsum-
mer—autumn months in 1911, the nearest year for which we have nitro-

gen figures. I note here that inconi])lete studies on the succession of

Algae, Protozoa, Rotifera, and Entomostraca in some of our down-
stream series of plankton-catches suggest that a good part of the loss in

plankton below Havana in the spring months during rising pulses of En-
tomostraca may be due to internal consumption, within the plankton
population itself. In May, 1899, in fact, these four groups of micro-

organisms showed a progression in reaching their maximum abun-
dance, each at a station farther down stream. In the circumstances the

presumption seems strong that each pound of Cyclopidae or Rotifera

taken near the mouth of the river represents several pounds of smaller

plankton species eaten farther up stream. (See tables, pp. I-jS, 459.)

5. Coincidence of Richer and Poorer Plankton and Bottom-

Fauna Reaches in the River below Chillicothe

The fact that there are shown, on a basis of the plankton and bot-

tom-fauna figures (1899—1915), such close coincidences between the

location and extent of the richer and poorer plankton and bottom-fauna
reaches between Chillicothe and the mouth of the river is not, I think, to

be taken too qtiickly as in itself dependable evidence that the bottom
fauna is to any certain and large extent a simple function of the vol-

ume or weight of plankton above it. Not only, however, does it appear

that both in its bottom fauna and its plankton stocks the sixty odd miles

of low-sloped river channel between Chillicothe and Havana is far

richer on the average than the lower river reaches, but the decrease

down stream, on a broad scale, is in each ca^e found to be progressive,

and in fact in substantially similar ratios, if the comparison is made with
the midsummer plankton figures. (Table, page 460.) The finding, on the

contrary, in August 191.3, in a local section of low-sloped channel in the

lower river, of a rich plankton-consuming population of Sphaeriidae

that was apparently not far from as rich as the best found in 1915 in

the middle Illinois Valley district suggests that the very general lack

of a suitable substratum for small Mollusca in the channel of the Illi-

nois below Lagrange may have more to do with the decrease of the

bottom fauna in the lower river than the decrease in the stock of plank-

ton above it. Other influences that may have some bearing on the aver-

age very poor showing made by the bottom fauna in the lower river in

1915 will be taken up farther on.



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461

6. The Plankton of Thompson Lake, 1909—1910

As shown by volumes per cubic meter of silk plankton, based on
vertical samples, the middle of Thompson Lake and the river channel

at Havana averaged nearly the same in plankton content during the four

months March—June, 1910 (Thompson, 13.77 c.c. ; river, 13.98 c.c.)
;

while in the July—November period of five months Thompson Lake
(5.21 c.c.) averaged about six times as rich as the river (0.87 c.c).

Expressed in terms of pounds per acre to a depth of one meter, these

volumes of plankton amount to around 114 lbs. for the lake and 124 lbs.

for the river in the March—June period, and to 46 lbs. for the lake

and 8 lbs. for the river in July—November. If these quantities of silk

plankton are multiplied, both in the case of the river and the lake, by the

Kofoid silk-filter-paper ratios for river samples, 1897—1899, the pound-
ages for March—June would be about twice those just given, and
for July—November about four times those figures. On the other

hand, if depth is taken into account, and total amounts of plankton
standing over an acre in the river and the lake to the full average depth
at the collecting station are figured, the river acre in March—June will be
found to have more plankton standing over it at a given time than an equal

area in the central portion of Thompson Lake ; and in July—November,
about half as much, instead of only one sixth as much, as an acre in the

lake.

Pl.^nkton Thompson Lake and Ilunois Rr'er, Havana, 9 months.
]VlABCH NOTCSfBER, 1909—1910



462

General Comparison of the Illinois River and its Connecting

Lakes in the Food Resources of a Fishery and in

Fish Output

Bottom and Limnetic Nitrogen, Plankton, etc.

In the fact that the Ilhnois Valley lakes, only in a lesser degree than

the river itself, are in the spring or later flood-seasons of all but very ex-

ceptional years open to receive the sewage-laden water from the upper

Illinois River and the Chicago Sanitary Canal, they differ materially

from the isolated glacial type of lake and from ponds or other waters

which are closed throughout the year to outside sources of nutriment.

Such supplies as the river lakes receive, they are able to retain in great

measure when their outflow is reduced to little or nothing by the falling

of the water levels, but the acquired resources of the river are contin-

ually drained away by the current, these losses being especially heavy

when the bottom sediments are being stirred up and scoured out in times

of flood. Hence the river, as we have seen, is not able to accumulate

and hold, even in the reach of extremely low-slope between Copperas

Creek dam and Lagrange, surplus stocks of these substances and the resi-

dues from their decay as large as the stocks found in the lakes, whether

in their deeper open, or in their weedy littoral portions ; while in the

relatively swifter channel below the Lagrange dam the difference is still

further emphasized. So far as the plankton alone is concerned, the sur-

plus stocks on hand at a given time per cubic meter of water in Thomp-
son Lake in 1909—1910 exceeded those in the richest part of the river

at Havana, opposite, at whatever season, with the percentage of diiTer-

ence in favor of the lake largest during the more critical season of low

productivity, July—November.

That the central Illinois Valley lakes are also to a considerable ex-

tent their own furnishers, through the growth and decay of shore vege-

tation, of their permanent stocks or organic food-materials, is suggested

by the size of the annual crops or aquatic vegetation, some of which is

rooted, in their shallower zones ; as well as by the fact that the stocks of

nitrogen, organic carbon and other oxidizable substances in the upper

layer of bottom soil are appreciably larger in the weedy littoral than in the

deeper open water. The river, whether in the Havana district or above

or below, has as offset extremely little weedy shore, where rich stocks

of similar kind can originate and decay, or where permanent lodgment

can be furnished for settling suspended organic matters carried in from

points up stream.

Bottom and Shore Fauna

In the case both of the plankton and of the various other food sub-

stances directly or indirectly usable as food by the 'bottom and shore ani-

mals, our data, as far as they go. point clearly to the presence at all



463

times, both in the river and in the lakes, of surplus stocks of a size far

more than sufficient to supply the immediate needs even of vastly richer

bottom and shore populations than we found in 1914—1915. But though
the river, at least in the region of low slope between Chillicothe and Ha-
vana, could thus theoretically produce as large poundages of bottom and
shore fauna as the lakes, or even larger, the figures for stocks on hand
in the two years mentioned, as well as other evidence, tend rather to

prove that the lakes are over their average acreage the better producers,

and that their richest fauna is developed in the weedy littoral, where also

occur the largest deposits of nitrogen, organic carbon, and other oxidiza-

ble matters.

As the margin between the bottom and shore fauna stocks on hand
in 1914—1915, even in the most productive lake and river areas, and the

food requirements, in kind, of a normal fish population, as of 190S and
neighboring years, seems clearly to be very much smaller than that be-

tween the supplies and the needs of the bottom and shore fauna itself,

it may be supposed that figures for stocks on hand after four or five

months' feeding by fishes can not be accepted as they stand, quite as

confidently as plankton and nitrogen figures for use as an index of

actual total productivity. If this is the case, and if it is also true, as we
have reason to think, that the lakes rather than the river are not only

the favorite feeding-grounds of the greater part of the large bottom-
feeding fishes during the 9-months growing season but also the largest

producers of fish flesh, then we should expect that complete figures for

total annual yield of bottom and shore invertebrates for the river and
lake acreage iri the Havana district would show a yet greater difference

in favor of the lakes than is shown by the figures of stocks on hand as

of July—October, 1914—1915. A further point in favor of the lakes

is the fact that the very heavy bottom-fauna poundages of the river

channel just above Havana consist largely of heavy-shelled snails, which
we can not believe are easily made use of as food by any but the largest

bottom-feeding fishes. Looked at in this way. the richest river valua-

tions may represent accumulation in the presence of light feeding; while

the lower poundages of bottom animals in the lakes opposite may be

looked upon as residues from originally much larger stocks, fed down to

a closer point than the river stocks, in consequence both of a relatively

greater size-availability and of their location within the main-feeding
range.

Fish Yields

On a plain acreage basis the total river acreage, at a gage of 10 feet,

Beardstown*. between La Salle and Grafton, with equal productivity as-

sumed in both river and lakes, should in 190,St have supplied around
18% of the total fish yield of that year, and the lakes about 82%. In

* Gage selected by Alvord and Burdick as that prevailing on an average one
half of the year, 1900—1913.

t Last year for which we have full fl§rures for fish yields.



4G4

the same year the river between Copperas Creek dam and Lagrange dam,
where the lake acreage is largest rejatively to the total, should have
furnished about 10% of the total fish yield ; the river between La Salle

and Copperas Creek dam, about 17% ; and the river below Lagrange,
about 37%. That the river and lake yields of fish per acre are not equal,

however, is suggested with considerable force by more than one consid-
eration. The first of these is the fact that in all the recent years for

which we have records the largest poundages of fish per acre have been
taken in the reaches with the largest quotas of connecting lake-acreage.

Taking the year 1908 as an illustration, and using the figures for sep-

arate shipping points obtained by the Illinois Fish Commission in that

year, we find for the 59.3 miles of river and lakes between Copperas
Creek dam and Lagrange dam, with about 90% of its acreage consisting

of lakes and ponds, an average fish-yield per acre for water levels pre-

vailing half the year, of 178.4 pounds; for the. 87 miles from La Salle

to Copperas Creek dam, with about 83% lakes, 130.4 pounds; and for

the lower 77 miles, Lagrange to Grafton, with around 63% lakes, only
69.8 pounds.

If, again, we seek to reach conclusions concerning fish yields for

the central Illinois Valley district from the bottom- and shore-fauna

data of 1914—1915 we can only suppose that the average yield of the

river per acre in recent years between the Copperas Creek and Lagrange
dams (with 705 lbs. bottom fauna average) has amounted to less than

half the average yield of the lakes opposite (with 1,447 -|- lbs. bottom-
and weed-fauna average). Or, to put it another way, while the river's

quota of the total fish catch in this reach on a plain acreage basis in 1908

was 10%, its capacity on a basis of the bottom- and shore-fauna figures

of 1914—1915 uncorrected, stands at about 5% of the total.

That both the river and the lake yields of fish per acre have been
lower in recent years in the reach above Copperas Creek dam and in the

reach below Lagrange than in the district between, is suggested both by
our bottom-fauna data from the river and by such incomplete figures as

we have from Peoria Lake and Meredosia Bay (1913 and 1914), and
also by the fact that the diiiferences in fish yield per acre in 1908 between
those two reaches and the Havana section are much greater than the

difference in the ratios of lake to total acreage. That, however, the per

cent, decrease in fish-yield in the lakes in these two reaches is less than

the decrease in the river may perhaps be accepted as circumstantially

proven by the greater decrease in the river bottom-fauna figures than in

the figures of fish yield themselves.



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Fish Catch, Illinois River and Lakes, 1908

(III. Pish Comm.)

La Salle to Copperas Creek dam



468

ratios estimated by Otterstroni* and Kronheimj for trout fed on raw fish

or ".'mostly animal food". The rate of consumption of bottom (or shore)
invertebrates per month for the nine-months "year" works out at about
S3 pounds

:

150 X 5

= 83.3

9

Expressing the bottom- and shore-fauna valuations of 1915 in mul-
tiples of the average monthly consumption rate, we find that in July

—

October of that year there were 120 miles of the Illinois River below
Havana whose average supplies of free-living bottom-invertebrates were
sufficient to last at such a rate only 30 days or less beyond the date of
collection ; and ?7.5 miles below Lagrange dam in which there were
sufficient stocks to last only 3 days. The much richer stocks in the river

above Havana, in spite of the exceedingly low valuations in the lower
river, were sufficient to bring up the average supply for the entire 180.5

miles between Chillicothe and Grafton to a figure of 3.1 months—which
was also the average for the 60.5 miles between Chillicothe and Cop-
peras Creek dam. In the reach of 59.3 miles between Copperas Creek
and Lagrange, where an average supply sufficient for 8.5 months was
found, there was a short stretch of 16.8 miles (immediately above Ha-
vana) where the stocks were sufficient to last for over 30 months, but a
relatively much greater part of the bottom fauna in this locally very rich

section was made up of large heavy-shelled Mollusca than was the case

in any other part of the river.

In contrast with all of these river figures except those for the 16.8-

mile reach between Copperas Creek and Havana, the average stock of

twelve lakes between Copperas Creek and Lagrange in July—October,
1914—1915, included a three months' supply of bottom fauna only for

the whole acreage, a minimum^ of 25.5 months' supply of shore animals

living above the bottom in the weedy acreage within the -l-foot line, and
a combined average supply of bottom- and shore-animals sufficient for

IT.-l months. (See table, p. -169.)

Supplies of bottom animals that were well above the average of all

the lakes studied, were shown by the Class I and Class II lakes (of the

type of Thompson and Quiver respectively) : average of five deeper
bottom-land lakes, 4.2 months ; average of two deep, sand-beach lakes,

10.2 months. Thompson Lake in 1914 had in August to October a 6.5

months' supply of bottom invertebrates over its entire acreage, and a
^85. 7 months' supply of weed animals in the 1—4-foot zones—or a com-
bined average supply, on a rough acreage basis, sufficient for 20.8

months. The low rating of bottom-fauna stocks in the very shallow
weedy lakes, such as Flag, Duck, Dennis, (0.6 to 1.1 months' supply),

* Fiskerei beretning. 1911. pp. 244—254.
t Bibl. der Gesamten Landwlrtschaft. Bd. 34, 1907.
} "Weed fauna" catches cover the upper 9 inches only.



469

was of little importance by comparison with the very high weed-fauna
figures from these lakes, the combined bottom and weed fauna averages
(if Crane Lake be excepted) apparently including a supply sufficient for

not less than 35 to 30 months. (See table, p. 4T0.)

Bottom and Shore Fauna as Foon for Fishery
1. Illinois Rr'er, July—October, 1915

Italic flgures=months' supply, at 83 lbs. per month, for 9 months' growing
season for fish-weight-increment of 150 lbs. per acre, feeding ratio 5:1.



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472

The Reproductive Rate of the Bottom Animals

Petersen, writing of the bottom fauna of the Danish fishing grounds,
1911—1918, has expressed the opinion that the bottom animals at least

reproduce themselves in weight each year. This conclusion was based
by Petersen on the observed fact that from year to year, on the average,

similar quantities of bottom animals are found over the same areas, along

with similar populations of bottom-feeding fishes. It is perhaps true that

more regularity in this respect might be expected in sea-bottom than in

the bottom muds of our relatively shallow inland rivers and lakes, which
are subject to extremes of temperature ; to floods and consequent wash-
ing and filling; to disturbance by seining and artificial dredging for navi-

gation channels ; and to other unfavorable influences.

With more particular reference to growth rates in small bottom
Mollusca, I note that Petersen (1911) remarks that a small Sphaerium-
like form, Abra sp., reproduces its weight several times in a year ; and
that F. C. Baker recently observed of very young specimens of the genus

Ampullaria, from Ceylon, that they doubled in size in an aquarium in

3 months.

Body weights taken by us of a series of 3 to 63-month specimens of

one of the commonest snails from the Illinois River and its connecting

lakes, Vivipara contcctoides, all from late July collections, 1913—1914,

indicate an average increase in body weight in one year running from 63

to 100% for the diflferent age-groups studied.



473

Lake containing 100 specimens, ages 3 months and upwards, taken in

late July, 1913. Out of 32 specimens over 32 months old, which were
capaljle of 87 to 101% increase in body weight in the next 12 months,

30 carried advanced embryos (midsummer brood) totaling 460.

Figuring the average increase in body weight of young and adult

age-groups in the next 12 months at 82.2%, the total body weight of the

entire collection (without embryos), which was 72.286 grams at date

of collection, would be approximately 131.7 grams one year later. Twelve
months' growth in the 460 embryos, assuming that all lived, might be

expected to amount in the average individual to at least 4/5 of the aver-

age body-weight of 12 to 15-month specimens (see table), or 233.6 mg.
each, making the total weight-increment in the 460 embryos in 12 months
107.4 grams. Adding the increase in the embryos and that in the young
and adults to the original total body-weight of the collection (72.3 grams)
we have, 12 months after date of collection, without making any allow-

ance for increase from a spring brood, a hypothetical total weight of

239.1 grams, or 3.3 times the weight with which we started.

PO.SSIBILITIES OF GROWTH OF VlVIPAR.\ CONTECTOIDES

(based OX COLLECTION FROM SEEBS LAKE, JL'LY 25, 1913)

Age groups (estimated')
Av. rate increase in
body-weight next

12 months

Advanced embryos
(of midsummer brood)

32 specimens over 27 months

6 specimens, 24—27 mos.

22 specimens, 12—15 mos.

40 specimens, 3—4 mos.

87—101%

91%

63%

82%

460 (in 30 specimens)

Total, 100 specimens 82.2%

Gross weight of collection, 94.0 grams.

Body weight (corrected for loss in alcohol) 72.3 grams
Increase in bOLly-weight next 12 months, at 82,2% 59.4 "

Increase in weight of embryos, next 12 months, at 233.6 mg.* each 107.4 "

Total 239.1 grams
=3.3 X original weight.

• » Equals % of weight of 12—15-mo. specimens (preceding table).



- 474

Changes in the Quantity of the Bottom-Fauna Stocks

between 1913 and 1915

Various conditions or agencies besides any heretofore mentioned

are doubtless capable of effecting local or temporary changes in the com-

position and weight of the bottom and shore animals either in the river

or the lakes. Among those peculiar to the river may be mentioned the

occasional scouring effect of floods in the regions of steepest slope, re-

sultant natural filling at points farther down stream, and the cutting away
of the river floor by artificial dredging for channel improvement. In the

lakes in which the heaviest commercial fishing is carried on, injury may
be done to the bottom animals in the fall of the year by the heavy tackle

used. Either in the river or in the backwaters variations of importance

in the size of the bottom-fauna stocks may doubtless result from changes

in the size of the population of bottom-feeding fishes, these variations

being in the direction either of decrease or accumulation. Mortality

from other unknown causes no doubt occurs at times, as seemed to be

the case with the larger snails in Quiver Lake between July 1914 and

July 1915. Of water pollution I note that this was not anywhere an im-

portant cause of mortality in the river bottom-fauna below Chillicothe up
to and including 1915.

Comparison of such data as we have for the season of 1913 with

the more complete results obtained in 1915 indicates generally a quite

satisfactory correspondence both in average composition and size of the

bottom-fauna stocks in the longer reaches of river channel between
Chillicothe and the Kampsville dam, both series of collections bringing

out clearly the contrast between the more productive reaches of channel

above Havana and the decidedly poorer stretches below. The most
important single point of disagreement between the 1913 and 1915 river-

figures concerns the finding in 1913 in the lower 30 miles, where in 1915

the average channel stocks of bottom animals were no larger than any-

where else in the lower 75 to 100 miles, of a rich local fauna of Sphaerii-

dae which apparently compared very well with the best found in the

rich Havana district. The presence, only locally, of so rich a bottom
population seems to imply the existence in that part of the river of

an adequate food supply, and is doubtless sufficiently explained other-

wise by its occurrence in a region of less than average slope and velocity

and more favorable conditions for sedimentation than are found in most
of the lower 100 or more miles of channel. For its disappearance be-

tween 1913 and 1915 no certain explanation offers. I note, however, that

it is in this wider, and on the average swifter portion of the channel that

bar formation is most frequent in the Illinois and that dredging opera-

tions for channel maintenance are oftenest carried on. It is also in this

part of the river, where for more than 70 miles the far greater portion

of the bottom-land lakes had been leveed and drained before 1915, that

sudden depletion of sporadic bottom-animal populations might most



475

easily be accomplished by the waves of large carp and buffalo that ad-

vance up the river every spring, and that have in recent years been

practically confined within the bank limits of the river itself for feeding

range luitil they have reached a point near or above the Lagrange dam.
The last hypothesis as an explanation of this single circumstance, and,

as well, of the comparative poverty of the bottom fauna of the entire

lower 77 miles of the river, receives some support from the fact that

while in 1915 the bottom-fauna stocks between Lagrange and Grafton

dropped nearly to the vanishing point, both in the channel and shore

zones, between Lagrange and Havana, where there was still a large lake-

acreage open to the river, the important decrease in the bottom fauna
over Havana district figures was to be seen only in the channel valua-

tions and was apparently, for the most part, explained by the character

of the channel bottom.

Only two of the twelve lakes in the Havana district (Thompson and
Quiver) were examined both in 1914 and 1915 with sufficient complete-
ness to permit a fair comparison of their stocks of bottom animals as of

these two years. While there was an increase of 60% in the average
quantities (by weight) in the deeper open water of Thompson Lake from
1914 to 1915, the changes in the shallower zones, and in both the deeper
and shallower areas in Quiver Lake, were in the direction of decrease,

Bottom-Fauna Stocks, Illinois River Channel, 1913 and 1915,

( July—October)

Reach



476

the percentages ranging from about 30 to ?0%. In Quiver Lake the

principal part of the decrease resulted from a heavy falling ofif in the

small MoUusca, the unusual numbers of dead snails found everywhere
in the lake in 1915 seeming to point to some exceptional mortality from
unexplained causes.

Bottom Fauna Stocks, Lakes in Vicinity op Havana, 1914 and 1915,

( July—October)



477

DETAILED VALUATION TABLES

I. Bottom Fauna, Illinois River, 1915

1. Chillicothe to Foot of Peoria Lake

8 Channel Collections. July 26—27 and Aug. 19

Chillicothe to Opposite Mossville

Campeloma subsolidum
Lioplax subcarinatus

Vivipara contectoides
Pleurocera sp.

Number per square yard Pounds per acre

17.3

39.7

28.2

3.0

51.9

47.6

141.0

3.6

Amnicola emarginata



478

16 Collections, 4- to 7-ft. Zone, July 26—27, Aug. 17—19, 1915

Chbllicothe to Opposite Mossville

Number per square yard Pounds per acre

Campeloma subsolidum



479

CpIiECTIONS, 1- TO 3-FT. ZoNE, JULY 26 AND 27, 1915

Chillicothe to Opposme MossvnxE



480

3 Channel Collections, July 28 and Aug. 19, 1915

Peoria Narrows



481

4 Collections, 4- to 7-ft. Zone, July 26—27, 1915

LowEB Lake, Opposite Eagle Packet Landing



482

2. Foot of Peoria Lake (Wesley) to Pekin

4 CHANNEa:, CoLu;cTioNS, July 22 and Aug. 19, 1915

Wesley to Pekin



483

3. Pekin to Copperas Creek Dam

14 Channel Collections, July 22, 23, 28, and Aug. 19, 1915

Pekin to Copperas Greek Dam

Number per square yard Pounds per acre

Campeloma subsolidum
Lioplax subcarinatus

Vivipara subpurpurea
Pleurocera sp.

17.1

2.6

2.1

7.0

51.3

3.1

10.5

8.4

Musculium transversum

Young Unionidae



484

7 Collections, 1- to 3-ft. Zone, July 22, 23, 1915

Pekin to Copperas CSeek Dam



485

4 Collections, 4- to 7-ft. Zone, Aug. 19, 1915

COPPEKAS Creek Dam to one Mile abo^t: Lr^EBPOOL

Number per square yard Pounds per acre

Canipeloma subsolidum
Lioplax subcarinatus
Vivipara contectoides
Vivipara subpurpurea
Pleurocera sp.

160.5

60.7

50.0 302.2

2.0

29.0

446.7

72.8

250.0

10.0

34.8

Musculium transversum 606.2 606.2

I

Leeches (small spp.)
[

76.0

Chironomid larvae (small spp.) 20.7

12.9

2.8

Channel Collections, July 31 and Aug. 3, 4, 1915

One Mile above Liverpool to Havana



486

13 Collections, 4- to 7-ft. Zone, July 31 and Aug. 4, 1915

One Mile above Liverpool to Havana

Number per square yard Pounds per acre

Campeloma subsolidum
Lioplax subcarinatus

Vivipara contectokles
Pleurocera sp.

48.8

41.9

22.8

7.3

164.4

50.2

114.0

S.7

Planorbis trivolvis

Musculium transversum
Sphaerium stamineum



487

5. Havana to Lagrange Dam, 1915

16 Channel Coixections, Aug. 2, 4, 5, 6, 27, 1915

Havana to Lageange Dam (42.5 Miles)



488

22 Collections, 4- to 7-ft. Zone, Aug. 2, 5, 6, 27, 1915

Havana to Lagrange Dam (42.5 Miles)



489

2 Channel Collections, Atjg. 6, 1915

Foot of Grand Island to Browning

(9-MILE section of NARROW, DEEP CHANNEL)



490

4 Collections, 1- to 3-ft. Zone, Aug. 6, 1915

Foot op Grand Island to Browning

(9-Mn^ section of narrow, deep channel)



491

5 Channex, Collections, Aug. 10, 1915

Valley City to Kampsville



492

8 Collections, 1- to 3-ft. Zone, Aug. 10, 1915

Valley City to Kampsville



493

12 Collections, 4- to 7-ft. Zone, Aug. 12, 22, 23, 1915

Head of Diamond Island to Grafton

Number per square yard Pounds per acre

Musculium transversum

Young Unionidae

4.4

1.3

2.2

2.6

Chironomid larvae (small spp.)
Corethra larvae
Hexagenia, etc. (nymphs)

Hydropsyclie larvae
Gomphid nymphs
Oligochaetes (small spp.)

1.4

0.5

5.5

0.9

0.1

2.9

0.2

trace
4.9

0.2

0.1

0.1

12 Collections, 1- to 3-ft. Zone, Aug. 12, 22, 23, 1915

Head of Diamond Island to Grafton



494

II. Bottom Fauna of the Lakes of the Illinois Valley, Copperas

Creek Dam to Lagrange, 1914—1915

1. Deeper, Bottom-Land Type (Clear-Mud, Liverpool,

Thompson, Dogfish, Sangamon Bay)

Clelab Lake, Sept. 1, 1915. Bottom Fauna
8 Coij:.ections, Depth, 8 to 8.5 ft. No Vegetation



495

Liverpool Lake, Sept. 1, 1915. Bottom Fauna
6 CoiiECTioNS, Depth, 6.5 to 9.5 ft. No Vegetation



496

Thompson Lake. Aug. 12—20, 1914. Bottom Fauna
8 Collections,* Depth, 7 to 9 ft.

(No vegetation; all mud bottom)



497

Thompson Lake, Aug. 12—20, 1914. Bottom Fauna
12 Collections,* Depth, 1 to 6 ft. All in Vegetation

(Eleven collections, mud bottom; one collection, sandy)



498

Thompson Lake, Aug. 12—20, 1914. Bottom Fauna
3 Sand-Bottom Collections,* Depth, 1 to 5 ft.

(Some vegetation)



499

Thompson Lake, Aug. 28, 1915. Bottom Fauna
7 Collections,* Depth, 1 to 6 ft.

(No vegetation; all mud bottom)

Number per square yard Pounds per acre

Campeloma subsolidum
Lloplax subcarinatus
Vivlpara contectoides

32.7

19.5

97.8

150.0
98.1

23.4

489.0

Valvata spp.



500

Thompson Lake,* Aug. 28, 1915. Bottom Fauna
5 Collections, Depth, 2 to 6 ft. All in Vegetation



501

Dogfish Lake, Aug. 18, 1914. Bottom Fauna
Collections, Depth, 6.5 to 7 ft. No Vegetation



502

Dogfish Lake, Aug. 31, 1915. Bottom Fauna
12 Collections, DsaPTH, 7.5 to 8.5 ft. No Vegetation



503

Sangamon Bay, Sept. 8, 1915. Bottom Fauna
8 Collections, Depth, 6.5 to 7.5 ft. No Vegetation



504

2. Deep, Sand-Beach Type (Quiver, M.\tanzas)

Quiver Lake, Sept. 30 to October 12, 1914. Bottom Fauna
15 Collections, Depth, 7 to 12 ft. No Vegetation



505

QurvEB Lake, Sept. 30 to October 12, 1914. Bottom Fatjxa

17 Collections, Depth, 1 to 6 ft.

(Most in vegetation)

Number per square yard Pounds per acre

C'ampeloma subsolidum
Lioplax subcarinatus

Vivipara contectoid'es

Pleurocera sp.

24.7

11,1

74.1

13.3

241.0

1.3

Amnicola emarginata



506

Quiver Lake, Aug. 30, 1915. Bottom Fauna
14 Collections, Depth, 1 to 6 ft. Most with Vegetation



507

Matanzas Lake, Sept. 4, 1915. Bottom Fauna
6 Collections (in Ceratophtllum and Pot.\iiogetox), Depth 2 to 6 ft.

(Some vegetation at all stations)



508

Flag Lake, Aug. 27—30, 1915. Bottom Fauna
15 Collections, Depth, 3.5 to 5 ft. Little Living Vegetation

•



509

Seebs Lake, Sept. 4, 1915. Bottoii Fauna

8 Collections, Depth, 2 to 5.5 ft. Little Vegeiaiiox



•510

i. Very Shallow, very Weedy Type (Duck, Dennis, Crane)

Dtjck—Denkis Lake, Oct. 2, 1914. Bottom Fauna
5 Collections, Depth, 2.5 to 4 ft. All in Vegetation

Number per square yard Pounds per acre

Valvata spp.

Physa, small sp.

Amnicola limosa
A. emarginata
Plsidium sp.

188.0

6.0

8.0

12.0

2.0

10.3

1.3

0.4 12.4

0.4

trace

Small leeches



ni

5. Dead Timber and Brush Areas

Dead Timber and Brush Areas, Vicinity of Havaka,* Aug. 18 to Oct. 16, 1914

BoTTOJi Fauna
6 Collections, Depth, 1.5 to 4 ft. Some Vegetation

Number per square yard



512

III. Weed Fauna, 1- to 4-Foot Zone, Lakes and Backwaters
in Vicinity of Havana, 1914

Dead Timber Ridge between Flag anu Thompson Lakes, Oct. 6, 1914,

Opposite "Warner's Cut," in Ceratophyixum and Algae
Weed Fauna, Upper 9 Inches (Depth, 2 ft.)



513

Middle of Duck Lake, Oct. 2, 1914, in Potamogetox pectixatus

Weed Fauna, Uppee 9 Inches (Depth, 4 ft.)



514

Foot of Thompson Lake, East Side, Aug. 14, 1914, in Ceratophyllum,

Smartweed, and Algae
Weed Fauna, Upper 9 Inches (Depth, 2.5 ft.)



515

Foot of Thompson Lake, Middle, Aug. 14, 1914, in Potamogeton pectinatus
Weed Fauna, Upper 9 Inches (Depth, 4.5 ft.)



516

Cedar Lake, August—October, 1916. Bottom Fauna
24 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation



517

Lake Zueich, August—October, 1916. Bottom Fauna
13 Collections, Littoral Zone. 1 to 7 ft. Some Vegetation



.-)18

LoxG Lake. Arcu'sx

—

Octouei!. 1916. Bottoji Fauna
6 Collections, Littoral Zone. 1 to 7 ft. Sojle Vegetation



519

PiSTAKEE Lake, August—October, 1916. Bottom Fauna
29 Collections, IjIttoral Zone, 1 to 7 ft. Some Vegetation

Goniobasis sp.

Number per square yard Pounds per acre

Sphaerium sp.

Pisidium sp.

Amnicolidae
Valvatidae
Physa spp.

Planorbis spp.

Unionidae, young

5.9

53.7

260.9

38.5

4.4

0.6

2.2

10.82 10.82

2.9

2.1

14.3

2.1

0.2

trace
4.4

Oligochaeta (small spp.)



520

Fox Lake (Including Mineola Bat), August—October, 1916. Bottom Fauna
28 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation



5-31

2. \\'eed Fauxa

Head of Pistakee Lake. August 17, 1916, ix CERAXoPHTLLfM
Weed Fauna, Upper 9 Inches (Depth, 3.5 ft.)



BIBLIOGRAPHY

Alvord, John W., and Burdick, Chas. B.

'15. The Illinois River and its bottomlands. Rep. 111. Rivers and
Lakes Commission, p. 1—14L

Baker, F. C.

'16. The Relation of mollusks to fish in Oneida Lake. N. Y. State

Coll. Forestry, Syracuse Univ., Tech. Pub. No. 4, p. 15—366.

'18. The productivity of invertebrate fish food on the bottom of

Oneida Lake, with special reference to mollusks. N. Y. State

Coll. Forestry, Syracuse Univ., Tech. Pub. No. 9, p. 1—264.

Board of Officers 'of the Corps of Engineers, U. S. Army
'05. Report upon a survey for a navigable waterway from Lock-

port, 111., to the mouth of the Illinois River. House of Repre-

sentatives, Doc. No. 263, 59th Congr., 1st Session, p. 1—544,

and charts.

Forbes, Stephen A., and Richardson, R. E.

'13. Studies on the biology of the upper Illinois River. Bui. 111.

State Lab. Nat. Hist., 9 (Art. X) : 481—574.

'19. Some recent changes in Illinois River biology. Bui. 111. Nat.

Hist. Surv., 13 (Art. VI) : 139—156.

Legislative Investigating Committee
'11. Report on the submerged and shore lands. Published under

direction of House of Representatives, 47th General Assembly,
State of Illinois. Vol. I, p. 1—191.

Muttkowski, R. A.

'18. The fauna of Lake Mendota. A qualitative and quantitative

survey, with special reference to the insects. Trans. Wis. Acad.
Sci. Arts and Letters, 19 ( Pt. I): 374—482.

Petersen, C. G. Joh., and Jensen, P. Boysen

'11. Valuation of the sea. I. Animal life of the sea bottom, its

food and quantity. Rep. Danish Biol. Station, 20 (1911) : 1—76.

Petersen, C. G. Joh.

'14. Valuation of the sea. II. The animal communities of the sea

bottom and their importance for marine zoography. Rep. Dan-
ish Biol. Station, 21 (1913): 1—44.

'18. The sea bottom and its production of fish food. A survey of

the work done in connection with valuation of Danish waters

from 1883 to 1917. Rep. Danish Biol. Station, 25 (1918) : 1—62.





PROFILE OF A SECTION OF THE ILLINOIS RIVER

Profile of the Illinois River from Chillicothe to Lagrange dam, showing

elevations of water surface at low gage of 1901, channel depths, and general

character of upper layer of bottom soils and sediments. The profile marks out

clearly the three deep, fiat-sloped, mud-bottomed, natural pools in which the

richest accumulations of small bottom-animals were found both in 1913 and

1915, viz.: the Peoria Lake pool, lying behind the great bar thrown up by Farm
Creek; the Havana pool, behind the great natural wier formed by the wash

from Spoon River; and the Sangamon pool, lying behind the high bar thrown

up by the mouths of the Sangamon. The data here used (elevations, soundings,

and borings) are from the report of the U. S. Engineers' Survey for a deep

waterway, House Document No. 263, 59th Congress, 1st session, Washington,

1905.



s:
too ^.



^:il^;^fe:l::^^-;::^:^:l;::|^^feilii::|;:^;;::H::::l:::il:i^:l,:J:,,J;i 4^frrlM^fi u ;i|-^^l4H4tH^;-^^l+^/T'ri^m^i^-^^^lt^





INDEX SHEET to the following maps of Illinois River and bottomland lakes,

Chlllicothe to Grafton. (After U. S, Engineers' Survey, 1902-1905,

House Doc. 263, 59tli Congr., 1st Session, 1905.)



^

^S;>^<;i e^j-j^

For non-tecnnicax ry. aee pa.ec



1. Grafton sheet.



.,'^<AQ8^'5J5.»\s'5t-

for non-tecnnicai



2. Kampsville sheet.





3. Meredosia sheet.



uj'

Ci?>.'i>^ o'b'viR,:^^ aNi"^

For non-tecnnicai suinmai j,





For non-tecnnicai





t For non-tecnmcai



6. Liverpool sheet.



For non-technical summary, see y<tsc



7. Peoria sheet.



A aii^s,.

For non-technical summary, see pa



8. Chillicothe sheet.