Bulletin STATE OF ILLINOIS Adlai E. Stevenson, Governor DEPARTMENT OF REGISTRATION AND EDUCATION C. Hon ART Engi.e, Direilor NATURAL HISTORY' S U R \^ E ^' D I \' I S 1 O N Harlow B. Mills, Chief olumc 25 BULLETIN Article 4 Biology of the White Crappie in Illinois DONALD F. HANSEN Printed by Autliorily of l/ie Slate of Illinois URBANA, ILLINOIS August J 951 STATE OF ILLINOIS Adlai E. Stevenson, Governor DEPARTMENT OF REGISTRATION AND EDUCATION C. HoBART Engle, Director A. E. Emerson, Ph.D., Biolosy L. H. Tiffany, Ph.D., Forestry L. R. HowsoN, B.S.C.E., C.E., Engineering BOARD OF NATURAL RESOURCES AND CONSERVATION C. HoBART Engle, Chairman George D. Stoddard, Ph.D., Litt.D., L.H.D.,; LL.D., President oj the University of Illinois Walter H. Newhouse, Ph.D., Geology Roger Adams, Ph.D., D.Sc, Chemistry NATURAL HISTORY SURVEY DIVISION Urbana, Illinois Scientific and Technical Staff Harlow B. Mills, Ph.D., Chief Bessie B. East, M.S., Assistant to the Chief Section of Economic Entomology George C. Decker, Ph.D., Entomologist and Head J. H. Bigger, M.S., Entomologist L. L. English, Ph.D., Entomologist C. J. Weinman, Ph.D., Entomologist S. C. Chandler, B.S., Associate Entomologist Willis N. Bruce, M.A., Associate Entomologist John M. Wright, M.A., Assistant Entomologist W. H. Luckmann, M.S., Assistant Enloinologist H. B. Petty, M.A., Associate in Entomology Extension James M. Bann, B.S., Research Assistant Paul Suranyi, Ph.D., Laboratory Assistant Sue E. Watkins, Technical Assistant Section of Faunistic Surveys and Insect Identification H. H. Ross, Ph.D., Systematic Entomologist and Head Milton W. Sanderson, Ph.D., Associate Tax- onomist Lewis J. Stannard, Jr., M.S., Assistant Tax- onomist Leonora K. Gloyd, M.S., Laboratory Assistant Philip W. Smith, B.S., Laboratory Assistant William R. Richards, B.S., Laboratory Assistant Grace H. Hull, Technical Assistant Section of Publications and Public Rela- tions James S. Ayars, B.S., Technical Editor and Head Blanche P. Young, B.A., Assistant Technical Editor William E. Clark, Assistant Technical Pho- tographer James W. Curfman, B.S., Technical Assistant Section of Forestry WiLLET N. Wandell, M.F., Forester and Head Lawson B. Culver, B.S., Associate in Forestry Extension Ross J. Miller, M.S., Field Ecologist Charlotte Aschbacher, B.A., Technical Assist- ant Section of Applied Botany and Plant Pa- thology Leo R. Tehon, Ph.D., Botanist and Head J. Cedric Carter, Ph.D., Plant Pathologist J. L. Forsberg, M.S., Associate Plant Patholo gist G. H. Boewe, M.S., Assistant Plant Pathologis Robert A. Evers, M.S., Assistant Botanist E. a. Curl, M.S., Special Research Assistant Sylvia Wolcyrz, M.S., Special Research Assist ant Rovenia F. Fitz-Gerald, A.B., Technical As sistant Section of Aquatic Biology George W. Bennett, Ph.D., Aquatic Biologis and Head William C. Starrett, Ph.D., Associate Aqiialii Biologist Donald F. Hansen, Ph.D., Assistant Aqualit Biologist R. W. Larimore, Ph.D., Research Assistant Walter H. Hart, Field Assistant Leonard Durham, M.S., Technical Assistant* ' QuENTiN Pickering, M.A., Technical Assistant' William M. Bain, B.A., Technical Assistant' Section of Game Research and Manage- ment T. G. Scott, Ph.D., Game Specialist and Heac Ralph E. Yeatter, Ph.D., Game Specialist Frank C. Bellrose, B.S., Associate Game Spti cialist H. C. Hanson, M.S., Assistant Game Specialisu James S. Jordan, M.F., Assistant Game Tech:' nician George C. Arthur, B.S., Project Leader^ Lysle R. Pietsch, M.F., Project Leader\ John C. Calhoun, B.S., Assistant Project Leader] Technical Library Marguerite Simmons, M.A., M.S., Technica Librarian Ruth Warrick, B.S., Assistant Technical Libra rian Consultant in Herpetology: Hobart M. Smith, Ph.D., Assistant Professor of Zoology, University oJ Illinois. Employed by the Illinois Department of Conservation and assigned to the Natural History Survey for adminis- trative and technical supervision. tEmployed by the Illinois Department of Conservation under terms of the Federal Aid in Wildlife Restoration Acl and assigned to the Natural History Survey for administrative and technical supervision. This paper is a citntrihution from the Sectian of Aquatic Biology. (20-140—4M—12-50) CONTENTS .cknowledcmknts 211 Iethods and Techniques 212 Collections 212 Length Measurements 212 Weight Measurements 21,i iilentification of Sexes 214 Scale Collections 214 Scale Analyses 214 Sampling Procedure 214 Periods ot Study 215 Study Limitations 215 RAi'iME Distribution 215 (EscRii'Tiox OF Lake Decatur 216 PORT FlSHlNT, 219 ET Sampling 221 Seasonal Variations 222 Species Variations 222 OODS 225 IlCRATIONS 225 EACTioN TO Current 225 EPRODUCTION 226 Sexual Maturity 226 Breeding Coloration 226 Spawning Season 227 Changes in Ovary Size 227 Nesting H abits 228 Sex Ratios 2.?0 •ISEASK 234 RNORMAI.ITIKS 234 Color and Structure 234 Excessive Sliminess 235 ONDiTiON OR Plumpness 235 Seasonal Changes in K Values 235 Possible Reasons for K Loss 243 OE AND Growth 244 Age Determination 244 Size and Age Distribution 247 Annual Growth Perio' Dr. George W. Bennett, Dr. Elizabeth B. Chase, and James S. Avars, and parts were read by Agnes C Hansen and Dr. William C. Starrett. Each offered valu- able criticism. I am especially indebted to Dr. Ben- nett and Dr. Thompson for what they have contributed through discussion. METHODS AND TECHNIQUES Because the white crappies used in this study were taken from a number of dif- ferent waters, by different collectors, and over a considerable period of time, several methods of collection and techniques of study are represented. Collections With the exception of two collections from hook-and-line catches, all of the fish taken from Lake Decatur for this study were trapped in 1 -inch-mesh hoop nets, that is, fykes or wing nets, each having a pot or rear compartment of 1-inch mesh (square measure). Most of the fish from other waters also were taken with 1-inch mesh hoop nets, but some fish were taken with hoop nets and seines of other mesh sizes, with hook and line, with rotenone poison, and by draining lakes. The methods of capture are specified through- out the paper in connection with discus- sion of the data. The 1 -inch-mesh hoop nets retain white crappies as small as 4 inches total length. The fish of this length arc usually a little over a year old. No effort was made at Lake Decatur to sample fish of lengths less than 4 inches. Hoop nets of the type used at Decatur and at most other collecting stations are made of netting stretched over a series of wooden hoops to form a cylinder 10 or 12 feet long and usually 31/? to 412 feet in diameter. Each net is divided into two compartments. A funnel-shaped entrance leads fish into a front compartment ; a second funnel leads them into a rear com- partment or pot. A "fingerthroat" is used at the inner funnel opening to help pre- vent reverse movement, that is, prevent escape of fish from the pot. Wings 10 feet long are attached on either side of the hoop at the open end and serve to guide Hsh into the trap. Ordinarily a separate lead net, 40 to 60 feet long, is used with each hoop net. Two poles, one at the outer end of each of the wings, and a third, at the end of the pot, are pushed into the lake or stream bottom to hold the net in the "set" position. The lead net is secured in a similar manner. The mesh of the lead, wings, and front compartment of the hoop net is 1 J/^ inches square, while the mesh of the rear compartment, or pot, is 1 inch square. Designations of mesh size of hoop nets mentioned in this paper refer to the mesh of the pot. At Lake Decatur and elsewhere, the hoop nets were set usually with a few inches of net standing out of water. For example, a 3 1/^ -foot-diameter net was set where the water was about 3 feet deep. The period between setting the nets and emptying them varied ordinarily from 1 to 3 days. Two winter hoop-net collections were made at Lake Decatur after the forma- tion of heavy ice over most of the lake. In January, 1938, nets were set in a place that was kept open by warm water from the A. E. Staley plant. This water, which flowed into the lake from a ditch just above Nelson Park, fig. I, originally was pumped from the lake into a cooling sys- tem within the plant, where in the cool- ing operation it was warmed ; it was then returned to the lake. In January, 1939, the nets were set in an open area between the old and new Illinois Terminal Rail- road bridges, three-fourths of a mile below Faries Park, fig. 1, on the upper west side of Lake Decatur. Neither at Lake De- catur nor elsewhere were nets operated under the ice. Length Measurements Most white crappies included in this study were measured in inches, to the nearest tenth of an inch, on calibrated measuring boards. The 1933 collection of crappies from Senachwine Lake was meas- ured in millimeters. Standard length was the basis of measurement before January, 1939, and total length after that date. Total length was measured from the tip of the lower jaw to the end of the longest ray of the tail with the mouth of the fish closed and August, 1951 7 V̂,, Hansen: Bioi.ogv of tiil \V'hit[; Crai'IMe '\u '^^^:Mi Fij. 1.—Lake Decatur and connecting streams, from the U.S. Coast and Geodetic Survey Decatur Quadrangle. with the rays of the tail laid parallel rather than fanned. Standard length was measured from the tip of the lower jaw to the crease at the base of the tail. This crease marks the anterior end of caudal rays and is a little forward of the last scales on the tail. The standard-length measurements were converted into total lengths for this paper, except that stand- ard lengths were used in computing coeffi- cients of condition and in discussing length-weight relationships. Length classes are designated in this paper by class center. Three different class intervals were used: one-half inch, 1 inch, and 1 '/> inches. Fish were assigned to length classes as illustrated by the fol- lowing examples from the class intervals: One-half-inch class interval: 5-inch class (4.8-5.2 inches) ; 5i/-inch class (5.3-5.7 inches). 1-inch class interval: 5-inch class (4.6- 5.5 inches) ; 6-inch class (5.6-6.5 inches). 1 1 >-inch class interval : 6-inch class (5.3-6.7 inches); 7ij-inch class (6.S- 8.2 inches). Weight Measurements Lake Decatur crappies were weighed on a Chatillon dietetic spring balance of 1,000 grams capacity. The dial of the scale was marked at 4-gram intervals, and readings were made to the nearest 4-grani mark. 214 Illinois Natural History Survey Bulletin Vol. 25, Art. A The fish were iced if necessary to prevent their spoiling when more than a day was required to handle large collections. The 1933 Senachwine Lake crappies 2 inches or more in length were weighed to the nearest one-tenth gram ; those less than 2 inches long were weighed to the nearest one-hundredth gram. The crappies from Horseshoe Lake and Craborchard Lake were weighed to the nearest one-hun- dredth pound. The Senachwine Lake crappies were carefully wiped to remove excess water before being weighed. This practice was not followed elsewhere. During the first several hours after death it is possible that fish, if kept in water, gain slightly in weight. Repeated weighings of a white crappie that before death had a total length of 8.5 inches and a weight of 148 grams showed after death a weight increase of 2 grams in 4 hours and 6 grams in 7 hours. This fish was kept in ice water between weighings. There may also be a slight decrease in body length after death which, together with the increase in dead weight over live weight, would tend to give a dead fish a higher coefficient of condition than a live one. Whether this weight change is typi- cal or not, it probably had only a minor efifect on the conclusions reached from the length-weight study of the Lake Decatur fish, since measuring and weighing usually were completed within 4 to 5 hours after the fish were removed from the nets. Identification of Sexes Differences in breeding coloration were not usually relied upon as a method of distinguishing sex. This method was used for a single collection (June 2-5, 1947) at Lake Decatur, and was also used by Dr. David H. Thompson for his observa- tions on sex in the Illinois River valley in 1942. As shown by tests, however, this method is not entirely reliable, and the rule at Lake Decatur was to dissect a fish when neither eggs nor sperm could be squeezed from the genital opening. Scale Collections Thirty to 50 scales were removed from the left side of each fish in the region between the dorsal spines and the lateral line. At Lake Decatur, to avoid the acci- dental mixing of scale samples, scaling tools were rinsed after scales had been taken from each fish. Scale Analyses Fish ages were determined by counting the number of annual rings on the scales. About half the scale examinations were made with a low-power, binocular, dis- secting microscope on uncleaned, un- mounted, dry scales. The other examina- tions were made from the projected images of cleaned scales mounted on slides in glycerine jelly or Farrant's medium. Interpretation of the growth rings is discussed in the section that deals with age and growth. Age readings were made on practically all white crappie scale material collected in Illinois for the Natural His- tory Survey up to January, 1939, and on some material collected later. With the following exceptions, age de- terminations are those of the author : Lynn Hutchens read the scales collected at North Lake, November, 1931, Lake Chau- tauqua, November, 1936, and Weldon Springs Lake, July, 1936; William Hoycr (National Youth Administration) read the scales collected at Senachwine Lake, August-November, 1933. Hutchens read the Lake Decatur scales collected in March-August, 1937; most of the June -August collections of that year were re- examined by the author. Sampling Procedure At Lake Decatur, and usually else- where, data from hoop nets were obtained from entire catches ; no attempt was made to select fish of any particular size. How- ever, about one-third of the scale mate- rial from the rest of the state was col- lected during a Natural History Survey tagging experiment in which only speci- mens longer than 6 inches were used. Also, some of the fish which the Survey tagged were caught by commercial fishermen, and field notes did not always show whether these fishermen had furnished their entire catches or not. It can be assumed that anglers, from whom some of the data were obtained, did not in all cases keep all of their small fish. Aiifiust, 1951 Hansen: Biology of the White Crappie 215 Periods of Stud\' The over-all period co\ ered by the Lake Decatur collections was late November, 1935, to earl\ December, 1939. Lengtii measurements and scale samples were ob- tained from all Lake Decatur collections. Weighing was begun in early April, 1936, and continued through 1939. Sex, whether male or female, was recorded at two pe- riods, late May, 1936. through July, 1^)37, and November, 1938, through December, l')39; records were kept of ripe fisii taken at spawning time in 1936, 1937, and 1''39. Age readings and the stud\- of length- weight relationships were terminated with the collection of January 9, 1939. The later 1939 collections were used in the study of size distribution, sex ratio, and seasonal variations in rate of hoop-net capture. Study Limitations In certain phases of the Lake Decatur study, analyses were made on the basis of broods. Fish hatched in the same calendar year constituted a brood. Because the brood assignments in collections made in ALi\ and June, 1936, at the time of an- nulus formation were thought to be par- ticularlv open to question, the collections taken during those months were not used in making certain analyses. In general, the study of broods was limited to those from which fish were taken in greatest abundance over the longest periods. The older broods, which disappeared from net catches shortly after the beginning of <)bser\ations (broods hatched in 1930- 1*532), were omitted from most ana'yses. Some entire collections, or parts of col- lections, were omitted from consideration when a breakdown of data into several categories resulted in poor representation. Two cc)llectio:i dates that appear in some of the tables, one in May, 1937, and one in May, 1939, were based on obser- vations of fish caught b\- anglers. These dates are, therefore, not represented in the tables showing rate of catch in hoop nets. CRAPPIE DISTRIBUTION Both the white crappie and the black crappie were reported by Forbes & Rich- ardson (1920) as occurring in lakes and streams throughout Illinois. The black crappie was reported as the more common species in the glacial lakes of northeastern Illinois, and the white crappie as the more common in the creeks of the state. Relative abundance of the two species tends to vary sharply in hoop-net sampling, which has provided most of the recent data on distribution of crappies in this state. Although no assurance can be given that net sampling has been adequate in all the localities sampled, it is believed that the relative abundance of the two species has been correctly represented for the various categories of lakes and streams discussed. In all Illinois water-supply reservoirs that ha\e been intensively studied, white crappies were found to be more abundant than blacks. The whites made up at least 95 per cent, and the blacks 5 per cent or less, of the large number of crappies caught with hoop nets in three reservoirs, Decatur, Craborchard, and Pana ; the whites were the only crappies caught in Lake Springfield. The hoop-net observa- tions at Lake SpringHeld and Lake Deca- tur were verified by observations of the hook-and-line catch in these reservoirs. The predominance of white crappies in these reservoirs may be due to one or sev- eral factors, three of which are suggested here: (1) a possibly greater suitability of the reservoir habitat for white crappies, (21 a probable predominance of white crappies in feeder streams, (3) a possibly heavier artificial stocking of white crap- pies. In most ponds studied by the Natural History Survey, white crappies were found to outnumber blacks. In a poison census of 22 ponds of 12 acres each or smaller (Bennett 1943), both species were found in 14 ponds, only whites were found in 3, and only blacks in 3. In the 14 ponds in which both species were found, whites predominated by weight in 10, blacks in 1 ; only traces of the two species were found in 3 ponds. One possible explanation of the pre- dominance of whites in most of the ponds ma\' be the more common occurrence of these fish in "creeks" ( Forbes & Rich- ardson 1920), the source of many of the fish used in stocking ponds. The green 216 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 Fig. 2.—Public bathing beach at Nelson Park, Lake Decatur, in July, iy43. (Photograph from Decatur Herald-Review.) sunfish, a typical creek species, was found in all but 1 of the 22 ponds censused by Bennett. Another possible explanation may be a predominance of whites in the natural stocking that takes place from feeder streams or from nearby streams that overflow in times of high water. Still another explanation may be a greater suitability of the pond habitat for the whites. In bottomland lakes bordering the Illi- nois River, the predominance of one species over the other is not striking. Both species seem to be abundant. Of the crap- pies taken in a 1942 hoop-net survey of the Illinois River and its bottomland lakes, 56 per cent of the total crappie catch from the lakes were blacks. In collections from most of these lakes, the blacks predom- inated. In collections from the only two bottomland lakes sampled along the Ohio River, the whites predominated. In the main channel of the Illinois River, the predominance of the blacks is more pronounced than in the bordering lakes. Of the crappies taken from the main channel in the 1942 survey mentioned above, 73 per cent were blacks. Of the crappies taken in 1944 and 1946 hoop-net surveys of Mississippi River navigation pools (pools 12-26) extending from Du- buque, Iowa, downstream to Winfield, Missouri, approximately two-thirds were whites. Data on the following rivers in which both species of crappies occur may not give a true picture of relative abundance, since, in spite of intensive netting opera- tions, rather small numbers of crappies were caught. Records show that more blacks than whites were taken in the Des Plaines River, but that more whites than blacks were caught in the Rock, Kaskas- kia (Luce 1933), and Ohio Rivers. Hubbs & Lagler (1947) stated that the black crappie is less common than the white crappie in silty waters. The rela- tion between siltiness and the predomi- nance of one species over the other is not clearly apparent in the Illinois waters studied. The black crappie, for instance, predominates in some of the silty waters of the Illinois River valley as well as in comparatively non-silty glacial lakes of the northeastern corner of the state. DESCRIPTION OF LAKE DECATUR Lake Decatur, fig. 1, is a city water supply reservoir made in 1922 by dam- ming the Sangamon River at Decatur, 75 miles below its source. While the lake was built primarily to meet the home and August, 1951 Hansen: Biology of the White Crappie 217 industrial water needs of a manufacturinj; center, recreational uses that include fish- ing, swimming, and boating are encour- aged by the city, figs. 2 and 3. The lake is 10.4 miles long and varies from one-fourth to three-fourths of a mile in width ; its original area was 2,805 acres. In 1*536 Glymph & Jones (1937) found a depth of 15 teet at the dam and a depth of 6 feet midway in the lake between upper and lower ends. Oxygen analyses made on July 29, i-i^. 3. — bail buaiiiig llerald-Revie^v.) ua Lake Decatur; the Alaha in Vii'). (Photograph from Decatur 218 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 1932, by D. J. O'Donnell, then of the Natural History Survey, indicated a fairly uniform distribution of dissolved ox>gen from surface to bottom. Ice covers most of the lake for about 2 or 2i/> months of the year. Some dates of 1936-1946. In The Story of a Lake, Walker (1949) has given a popular ac- count of the silting of Lake Decatur. The turbid condition of Lake Decatur probably accounted for the scarcity of aquatic plants at the time of this study. Table 1.—Species and numbers of fish caught in 1-inch mesh hoop nets at Lake Decatur during the period April, 1936, through September, 1937. Species* Shortnose gar, Lepisosleus platostomus Rafinesque Gizzard shad, Dorosoma cepedianum (Le Sueur) BufFalofishes, Megastomalohus cyprinella (Valenciennes), Ictiobus ««^fr {Rafinesque), /. bubalus (Rafinesque) Carpsucker, Carpiodes sp Spotted sucker, Minytrema melanops (Rafinesque) White sucker, Catostomus commersonnii (Lacepede) Redhorse, Moxosloma sp Carp, Cyprinus carpio Linnaeus Golden shiner, Nolemigoniis crysokucas (Mitchill) Channel catfish, Ictalurus lacuslris (Walbaum) Yellow bullhead, Ameiurus natalis (Le Sueur) Black bullhead, Ameiurus melas (Rafinesque) Flathead catfish, Pilodiclis o/ivaris (Rafinesque) Pike, Eiox lucius Linnaeus White crappie, Pomoxis annularis Rafinesque Black crappie, Pomoxis nigro-maculalus (Le Sueur) Warmouth, Chaenobrytlus coronarius (Bartram) Green sunfish, Lepomis cyanellus Rafinesque Bluegill, Lepomis macrochirus Rafinesque Pumpkinseed, Lepomis gihhosus (Linnaeus) . ^ Largemouth black bass, Micropterus salmoides (Lacepede) Yellow perch, Perca flatescens (Mitchill) Yellow bass, Morone inlerrupta Gill Freshwater drum, Aplodinotus grunniens Rafinesque ind Number of Fish Caught 6 614 268 292 1 3 119 141 3 150 1 160 4 2 2,531 123 1 3 97 8 29 22 880 391 * Common and scientific names from American Fisheries Society Special Publication No. 1 (Anonymous 1948). ice departure were February 23, 1936, February 28, 1939, and March 13, 1940. Glymph & Jones (1937) showed that during the first 14 years of impoundment, 1922-1936, sediment had been laid down on the bottom to a depth that averaged 1 foot near the dam and increased gradually to 2 feet in the upper portion of the lake. Deposits of sediment from 3 to 7 feet thick were measured in the old river channel in the main part of the lake. The river chan- nel above the lake had remained quite clear of deposits as a result of the scouring action of floods. The accumulation of sediment in Lake Decatur had resulted in a loss of 14 per cent of the original storage capacity of the reservoir, or 1 per cent per year. According to Brown, Stall, & De Turk (1947), the rate of loss increased to 1.2 per cent per year during the period While in some places there were extensive beds of water primrose {Jussiaea sp.), arrowhead {Sagittaria sp.), and cattail {Typha sp.), most of the shore line was bare of emergent aquatic plants. No plants of strictly underwater habit were re- corded, although they may have been present in some areas. The bottom fauna of this lake was studied by Gersbacher (1937) and the plankton by Eddy (1932). A list of the species of fish and numbers of each kind caught in Lake Decatur with hoop nets from April, 1936, through Sep- tember, 1937, is shown in table 1. The species composition of anglers' catches at Lake Decatur as obseryed in partial cen- suses is shown in two tables : table 2, rep- resenting counts by the writer of the catches of 71 fishermen who were using August, 1951 Hansen: Biology of the White Crapime 219 Table 2.—Species and numbers of fish caught with live minnows by 71 bank fisher- men at Lake Decatur, as shown by stringer counts in May. 1937, and May. 1939. I 220 lii.iNois Natural. History Survey Bulletin Vol. 25, Art. 4 Large crappies arc uccasionallj caught on bass plugs. Worms and artificial Hy- roii baits are chective at times. Larry Simand.e, who, while living at Canton, often fished for crappies with artificial baits at Lake ^^ hautauqua, recommended the following Hy-rod baits: Paulson's Pilk (weedless) with pork rind, Pflueger Pilot (lies, Pflueger Pippin Wobbler, and four patterns in trout Hies—white miller, red ibis, royal coachman, brown hackle. Robert Page Lincoln, outdoor writer, is credited with describing a trolling lure that he considered as good a crappie bait as a live minnow. This bait consisted of a strip of freshly caught fish measuring a little over an inch in length (with skin on one side) placed on a hook belpw a one-half to three-quarter inch gold-plated spinner ; a 4-foot gut leader was used between the spinner shaft and line. A few fishermen employed special methods and were successful in catching crappies at Lake Decatur throughout the summer. The method described by E. F. Zehnpfund involved wading near the bank where the water was 1 or 2 feet deep and slowly bobbing a minnow up and down near projecting sticks and brush. This fisherman emphasized that where obvious cover, such as brush, was scarce he did not overlook the most isolated projecting weed stalk as a possible place to catch a fish. Robert Witke used a different method for catching crappies in the summer : A stake was driven into the lake bottom with 2 or 3 feet left projecting above the water. A line with hook attached was fastened to the top of the stake so that a live minnow placed on the hook was able to swim only in a small area close to the surface. The crappies then came to the surface to take the bait. ^ Mr. and Mrs. O. D. Zook of Spring- field have fished for white crappies in Lake Springfield for many i,ears and have es- tablished for themselves a local reputation as expert crappie fishermen. While most fishermen at Lake Springfield, like those at Lake Decatur, have difficulty in catch- ing crappies in midsummer Mr. and Mrs. Zook have usually been able to catch these fish from early spring to late fall by varying their fishing methods with season of the year. Thev use artificial lures as well as minnows. Mr. Zook, who special- izes in artificial fly-rod baits, has had success with a small spinner and white fly combination and with various all-metal baits (Pflueger Pippin Wobbler, Arbogast Tin Liz, South Bend Irix Oreno) andi with homemade baits patterned after thei baits named. He is of the opinion that tiiese metal baits arc improved by replac- ing their metal "flippers" with a strip of thin white rubber, one-eighth inch wide by 1 inch long, tapered to a point. He has used artificial lures mainly in his spring and fall fishing. The Zooks fish with minnows in shal- low water in the spring but in deep water in the summer ; in early spring from a bank where the water is only 1 or 2 feet deep, and later, in May and June, from a boat dock where the water is 6 to 8 feet deep. When the weather becomes hot and they can no longer catch crappies from the boat dock, they fish with minnows from a boat in a submerged creek channel at a depth of 10 to 15 feet. These two fisher- men believe that locating concentrations of fish is one aspect of successful crappie fishing and making the crappies bite is another. Mrs. Zook has written as follows: "Sometimes a foot in depth or a foot to one side or the other makes a difference of an empty or full stringer. I bob the min- now up and down—move it sideways through the water—change spots if it is only a few inches. I keep the minnow mov- ing constantly. If the crappies don't hit almost as soon as the minnow is dropped in, you may as well move around and ag- gravate them until the\' do hit. I know it is possible to do that. In the spring I saw a 14-inch crappie in the boat house; it took me 25 minutes to catch him. If ever a crappie was aggravated, he was. I dan- gled a minnow all over him—it was in- teresting how he would knock the minnow out of his way." The Zooks believe that crappies like to stay in and around brush and snags, and that these fish sometimes show a preference for small minnows over large minnows. Two Peoria Lake fishermen were sure that large-size crappies, kind not men- tioned, preferred small minnows while medium-size crappies were not so partic- ular about the size of the minnows. In Lake Springfield, where most of the crappies are fmall, the Zooks usually made August. 1951 Hansen: Bioi.oov of the White Craimme 221 their best catches of large crappies during the first 3 weeks in May and continued to make good catches of small crappies for several weeks longer. Manv (ishermen keep quite small crap- pies when large ones are scarce. Of 32 stringers containing white crappies exam- ined at Lake Springfield. AIa> 22-25, 1041. 30 stringers contained white crap- pies that measured 7 inches or less, total length. A grouping of the 2^6 white crap- pies found on the 32 stringers into half- inch length classes showed that 66 per cent fell in the 5]/>- to 7-inch classes, 27 per cent in the 7i/>- and 8-inch classes, and 7 per cent in the 8) j-inch class or above. NET SAMPLING in hoop-net fishing for crappies, varia- tions have been found in the rates of capture at different seasons; also, in the Table 4.—Seasonal variation in rate of capture of wtiite crappies in l-incti-mes)i hoop nets in Lake Decatur. D.*TE OF CoLLECTlOiV I03S Nov. 22 1036 .\pT\\3 Mav4-6 May 29-June4 lune 22 julv 3-5 julv 31-.Aue. 3 Sept. 8-14.. Sept. 22 Oct. 24-27 Dec. 21 1937 March 1-4 .April 24 June 3-S June 24 Julv 10-1 h .Aug. 6-14 iSept. 22. Sov. 3 I93S Jan. 17-24 March 14 Mav 28 Julv 1-14 Aue. 25 fJet. 6 Ps after the date of tagging. REACTION TO CURRENT At Lake Springfield, Sangamon County, in May, 1941, white crappies were ob- served concentrated in front of an 8-by- 1 0-foot wire screen fastened to a culvert that delivered a large volume of water into the lake from an electric power plant. The water coming from the culvert entered the lake at the lake level, that is, there \vas no fall. The crappies could be caught 226 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 readily with a dip net. In 11 dips with a circular net measuring 2 feet across, 60 white crappies were taken. These meas- ured 5 to 9 inches in length, averaging ahout 6 inches. Positive reaction to strong currents is, of course, well known for a number of species of fishes. No tempera- ture readings were obtained at the culvert outlet. REPRODUCTION Biologists regard a knowledge of the facts of fish reproduction as of special im- portance in their efforts to bring about population increases in certain species of iish. Both kinds of crappies in Illinois waters show a strong tendency to repro- duce in adequate numbers, so that artifi- cial aids to reproduction have so far not seemed necessary. It is possible that a knowledge of the facts of crappie breeding may prove to be of use in the development of methods of limiting already over- crowded populations. Sexual Maturity Sexual maturity in Illinois white crap- pies is reached at the end of the second or third year, that is, at an age of about 24 or 36 months. There is no indication that white crappies in Illinois ever spawn when 1 year old, although spawning at 1 year has been observed in Texas black crappies (Harper 1938). Only about a third of the white crappies hatched at Lake Chautau- qua in the spring of 1938 appeared to be approaching maturity as 2-year-olds (ages determined by scales and by size distribu- tion) when specimens were examined in May, 1940. In a sample of 127 2-year-old females examined on May 16, dissections showed that the ovaries of only 40 con- tained well-developed (large) eggs. The ovaries of the other 87 females of that age group were still in an immature stage and it was believed that none of this group of 87 2-year-olds would reach maturity during the 1940 spawning season. The 40 mature females averaged 6.2 inches total length, while females in which the eggs were undeveloped averaged 5.8 inches. Fully mature, 2-year-old white crappies (ages determined by scales) were captured at Lake Decatur on June 3-5, 1937; in- cluded were ripe individuals of both sexes. These fish averaged approximately 2 inches longer than the ones from Lake Chautauqua that did not ;eem to be maturing as 2-year-olds. Among 2-year-old white crappies exam- ined by Eschmejer, Stroud, & Jones (1944) from one of the reservoirs of the Tennessee River, some were mature and others were not. The smallest ripe white crappie ob- served in Illinois was a female of 5.6 inches, total length, caught on May 20, 1941, at Lake Springfield. The scales of this fish did not show clearly whether iis age was 2 or 3 years. Breeding Coloration The coloring of male and female white crappies is identical except during and near the spawning season, when the breed- ing males typically turn darker, while the females typically remain unchanged in color. The darker coloring of the male, darker in some individuals than in others, is most noticeable on the sides of the head, chin, and breast, and to a lesser extent on the sides of the body. It begins to appear in April, reaches maximum intensity about the last of May, and is lost in most males by the last of June. The disappearance of the breeding color seems to take place gradually, and some males retain remnants of the breeding pigmentation well into July. The following tests were made to dis- cover the degree of error in using breeding color as a basis for sex recognition in spring collections of white crappies. The fish were first sorted as to sex on the basis of color ; then they were opened and their reproductive organs were examined. In these tests, it was found that sex was usually guessed correctly, but that errors were sometimes made in fish large enough to be sexually mature as well as in small fish which may have been immature. At Lake Decatur, 100 specimens were examined in the period May 17-20, 1939. Among 19 white crappies first judged to to be males by their dark pigmentation, dissection showed 18 males and 1 very darkly pigmented female. Among 81 judged to be females by the absence of dark pigmentation, dissection showed 2 August. 1951 Hansen: Bioi.oc.v of niii White Craim'ie 227 males and 7*5 females. The true ratio \\ as 20 males ami 80 tcmalcs, instead of 10 males and —• COCOCOCSCSOJCOCO Ol OO OO t— I .-< CO CO CO CO C-J ro -^ 1—' CO CO ' cy\ oo ' On 'J^ oo coc-icsr-ir-icocococo cOCOCOfNC-JCNC^COCO (NCSCNCSCOCOCOCOCO CO CN c-i cs c^i rJ Ol CN CN CM r-i cs cs CO n c-icscscocococscscs cs cs rJ c-i cs cs cs cN rj c^i cs cs cs r-i cs CSCSCSCOCSCSCSCSCM O CO cs rj c^i ri cs cs o cs r-J cs cs cs cs cs cs in cs cs cs CO cs cs I I i;^:r--r r- ^ ^ *o ^ cs cs cs cs cs CO —I vO oo On — CO c^i ^^ "t* r-1 ^ cs cs cs cs cs cs I I I i:r I I I I I I I I I I I I I I I I o ^H VD O *• oi r^ ?; "^ 1^ ?; rJ ~ < —,^n C/2 O Q ^^ "^ to I TtH A 1 f^' - i^ r >. U U ^ Kn *-- ^' ^«g B-*s a 3 3 3 oj^; 1 ^ < ^ H-,H-.^-i< 1/3 Z r-L ^ CO ^ vj-i ; I lITi -C C< 2 IN so "^^ August, 1951 Hansun: Biolocy of the Whitk Crapi'IE 237 M—NOUIQNOO JO XN3IDUJ30D 238 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 crappies. White crappies over 7 inches (standard length) may be regarded as mature and those under 5 inches as imma- ture. The seasonal changes may be sum- marized as follows: Large sizes, crappies 7 inches standard length and smaller: Condition values in- creased rapidly through middle and late summer, reached a yearly peak in late fall or early winter, remained at a high level through the cold months, dropped sharply during the spring, and reached the lowest point in early summer. Small sizes, crappies 5 inches standard length and smaller: Condition values in- creased from the middle of spring through early summer, reached a yearly peak in midsummer, fell off through late summer and fall, remained stationary through the cold months, and fell again through early spring. _ Condition changes of crappies in the 6-inch class were approximately inter- mediate between changes described for fish of the two size classes discussed above. Differences between large and small fish with respect to condition changes may be summarized as follows: The small crappies began to fatten earlier in the growing season than the large crappies, reached peak condition in midsummer rather than late fall or early winter, and lost condition in spring and again in late summer and fall, rather than only in the spring and early summer. In fish that were less than 5 inches long at the start of the growing season and that grew to a length greater than 7 inches, the fall and subsequent spring changes in condition followed those de- scribed for the larger fish. Increases in K values occurred only during the annual growing period. Upward and downward trends in large and small fish described above for various seasons of the year have, for the most part, been based on observations made during 2 calendar years. The evidence of winter-to-spring drop in condition in large fish rests mainly on observations in 1937 when large sizes were abundant ; winter observations were lacking for 1935-36, and large fish were scarce in the first half of 1938. Fish of given sizes did not always show the same K values in corresponding months of different years. The 8-inch and 9-inch classes showed more uniformity in this respect than the smaller fish. A tendency for large fish to have higher K values than small ones was observed in the smallmouth bass by Bennett (1938), in the largemouth bass by Thompson & Bennett (1939), and in the bluegill by , Bennett, Thompson, & Parr (1940). Such: a relationship was also found in the Lakei Decatur white crappies but was unappar-i ent or inconspicuous at certain times of the year—especially in June and July. The similarity of K values in all sizes of white crappies at that time of year may be ascribed to two things : ( 1 ) Late winter and early spring weight losses were rela- tively greatei in large fish than in small ones (compare the changes in K values in the 6-inch to 9-inch classes from March to June, 1937) and (2) summer gains in K values started earlier in small fish than in large ones. Adequate data on the spread of K values are not available for June and July, 1938, because no collecting was at- tempted in June, and the July collection included only a few large fish. A limited number of comparisons be- tween K values of males and females of various lengths, table 16, indicates that the seasonal changes in condition occur in both sexes and that throughout the year K values tend to be a little higher in males than in females. Stroud (1948) found no important difference in plumpness between the sexes of black crappies in Norris Reser- voir, Tennessee. In black crappie collections made at sev- eral different times of year, Stroud ( 1948) did not find important differences in plumpness among four age categories or among size groups ranging from 4 to 12 inches. The failure of his data to show im- portant differences is perhaps explained by the fact that most of his collecting was done in the spring, which, as indicated by observations at Lake Decatur, is a time of year when large and small crappies are of similar plumpness. Changes in the average K value for members of various broods taken in the nets between early April, 1936, and early January, 1939, may be seen in table 17 and fig. 8. Broods represented in the nets by only a few specimens have been omit- ted from the table and graph. The longest August, 1951 Hansen : Bioi.ouv of the White Crafpie 239 period of observation of any brood was about 2 vears. A certain amount of re- semblance may be seen between the curves in rigs. 7 and 8. In general, the seasonal Table 15.—Examples of the distribution of coefficient of condition (K) in white crappies of four size categories, 6-9 inches standard length, at Lake Decatur, March 1-4, and June 24, 1937. These dates were arbitrarily selected. K Value 240 Illinois Natural History Survfy Bulletin V'ol. 25, Art. 4 August, 1951 Hansen: Bioi.ocv of the White Crai-pie 241 riuctuations in condition summarized for small risli were similar to those occurring in young fish, and the fluctuations sum- marized tor large fish were similar to those occurring in old fish. Uififerences in condi- tion between adjoining broods were, as a rule, small, unless members of the adjoin- ing broods difiered considerably in length. Late-summer trends in condition were especially variable from year to year in second-year fish, fig. 8. A late-summer rise in condition was observed in broods mak- ing good or moderately good late-summer growth (iqJ5 brood in 1936, and 1937 brood in 19381, but a late-summer loss of L'ondition was observed in a brood whose late-summer growth was small (1936 brood in 1937). The amount of late-sum- mer growth can be seen from the average lengths of fish printed along the curves in rig. 8. \\"ith reference to the condition changes in the 1935 brood in late summer of l')3b and the 1937 brood in late sum- mer of 1^^)38, it is apparent that while each brood, taken as a whole, showed a rise in condition, fig. 8, the smaller (4-inch and 5-inch fish, fig. 7) were losing condition. Eschmeyer, Stroud, & Jones ( 1944) ob- ser\ed condition changes in white crappies which the\ refer to as 2-year-olds (appar- ently the 1940 brood) at Chickamauga Reservoir, Tennessee, from March to October, 1942. This brood of white crap- pies reached peak condition in June and showed little change in condition from June to October, thus following the trends obser\ed in Lake Decatur crappies of simi- lar age and making the same sort of poor late-summer gro\vth. Measurements of condition of white crappies in three other Illinois lakes may be seen in table 18. Generalh , fish frcjm Table 17.—Seasonal fluctuations in average coefHcient of condition (K) in several broods of Lake Decatur white crappies. Figures in parentheses represent numbers of specimens. Date of Collection 1936 April 3 Mav4-6 Mav 29-June4 Iulv3-5 Iulv31 Aus. 3 sept. 8-14 Sept. 22 :>:t. 24-27 Dec. 21 \937 March 1-4 April 24 May 16* lune 3-S June 24 lulv 10-16 Aug. 6-14 Sept. 22 Vov. 3 ms fan. 17-24 March 14 Mav 28 [ulv 1 lulv 14 Aui!.2S Jet. 6 Sov. 4 11 1939 [an. 9 1933 Brood 2.80(152) 2.73 ( 18) 2.71 ( 59) 3.01 ( 5) 3.05 ( 3.47 ( 3.28 ( 3 . 20 ( 3.18 ( 4) 2) 1) 17) 18) 3.21 ( 53) 3.10 ( 14) 3.02 ( 10) 2.79 ( 32) 2.78 ( 27) 2.65 ( 15) 2.99 ( 2) 3.00 ( 2) 1934 Brood 2.28 (168) 2.50 ( 44) 2.70 ( 24) 2.99 ( 36) 3,02 ( 27) 3.15 ( 11) 2,97 ( 11) 3,17 (139) 3,22 (107) 3.16 (220) 3,02 ( 67) 3,07 ( 39) 2,72 (116) 2.72 ( 73) 2.56 (37) 2.96 ( 8) 2,76 ( 2) 3.17 ( 2) 3,36 ( 3.22 ( 3.06 ( 3) 14) 8) 1935 Brood 2.90 ( 51) 2,99 ( 14) 2,97 ( 49) 2,93 ( 69) 3.14 (171) 2.95 ( 67) 2.79 ( 35) 2.93 ( 37) 2,66 ( 62) 2,71 ( 27) 2,69 ( 29) 2.77 ( 13) 2.80 ( 7) 2.92 ( 3) 3.15 ( 16) 3.05 ( 4) 2,74 ( 4) 3,12 ( 2) 1936 Brood 2.66 ( 6) 2.70 ( 45) 2,59 (206) 2.45 (165) 2,47 ( 12) 2 40 (181) 2.26 ( 84) 2,54 ( 24) 2.75 ( 19) 3.05 ( 9) 2.89 ( 17J 3.06 ( 71) 1937 Brood 2.58 (56) 2.68 (59) 2,67 (49) 2.70(77) • Sample obtained from anglers. 242 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 o X a O o 15 6 > E \A •^fa < o 00 g /Vugust, 1931 Hansen: Bioi.ocv of the White Crappie 24J these l.nkes show an increase in K with in- crease in length. An exception may be cited in the Horseshoe Lake data, where the K value of the 5-inch class was con- siderably hijrher than the K values for the b-inch and 7-inch classes. The condition values of 13 white crap- pies taken at Crahorchard Lake in ALirch, 1944, were much higher than the \alues observed in crappies of the same size else- where in Illinois. In these Craborchard specimens, high condition had accom- panied rapid growth. Craborchard Lake was new in \9i9. These large Craborchard specimens were observed to be deep bodied in proportion to their lengths and unu- sually plump in their abdominal regions. The body ca\ities of dissected specimens cortained exceptionally large deposits of fat. No such large deposits were seen in the white crappies of Lake Decatur. In the same Craborchard collections, fish of small sizes appeared to be much less plump than those of large sizes, but they were not weighed and their K values were not de- termined. While working for the Natural Histor\ Survey at Senachwine Lake on July 31, 1933, Lyle E. Bamber measured and weighed 16 white crappies which ranged from 35 to 49 mm. (1.4 to 2.0 inches) standard length. From their lengths and the absence of annuli on their scales, the>' were judged to be about 2 months old. They were the only young-of-the-year crappies studied. Their K values varied from 2.01 to 2.46 (average 2.20). Length and weight measurements were made with the degree of accuracy desir.able for such small fish, as described in the section "Methods and Techniques." Collections of 4- to 7-inch white crap- pies measured at Senachwine Lake during the period August 18 to October 13, 1933, showed changes in condition that approxi- mately corresponded with the autumn changes in condition in 4- to 7-inch crap- pies at I^ake Decatur; the 4-, 5-, and 6- inch classes showed a loss in condition and the 7-inch class a slight rise in condition from August to October, table 1 8. Possible Reasons for K Loss The fact that spring was a time of sharp decline in plumpness of Lake Decatur \vhite /jrappies suggests a possible connec- tion between weight loss and spawning. The major weight loss in mature white crappies occurred over a 2-month period preceding the nesting season. It appears likely that, in the years we are dealing \Aith, most of the nesting took place within the period May 15 to June 15. Russell ( 1914) suggested that a prespawning con- dition loss in the haddock was caused by diversion of food materials to the ripening sex organs. But since two other species, the sardine studied h\ Clark (1928) and the bluegill studied b\ Bennett, Thompson, 5c Parr (1940), showed a rise in con- dition just before spawning and also since there was a spring loss of condition in im- mature crappies, it is appropriate to look for other explanations than the one offered bv Russell. Clark (1928), Mottley (1938), and Bennett, Thompson. 5c Parr (19401 all observed a loss in condition after spawning. The condition losses in mature white crappies are too large to be accounted for by reduction in weight of the ovaries and testes after spawning. Weighing of the gonads of a few white crappies ranging from 6.5 to 10 inches standard length showed that just before the spawning sea- son the ovary weight amounted to 6 per cent of the total body weight, and the testes weight amounted to less than 1 per cent of the total body weight, while the averaj:e winter-to-spring weight loss of the entire fish amounted to about 1 5 per cent in both sexes. It was found, as already mentioned, that small white crappies underwent a loss in condition in late summer and fall when they were increasing slowly in length. The possibility can be disregarded that the spring condition loss of larger fish was brought about by growth in length of the crappies without sufficient gain in weight to maintain K values at a constant level. Annulus formation studies showed that onl) a few of the mature Lake Decatur white crappies had started their 1937 growth by early June, and that the major- ity delayed their 1937 growth until Jul\ or August. Thus, at the time of their spring loss in condition, the large crappies were not growing in length. Other possible reasons for spring con- dition loss among white crappies include 244 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 disease, seasonal scarcity of fattening foods (or food in general), and difficult feeding conditions resulting from high turbidity. Disease as a possible reason for weight loss is suggested by the apparent high summer mortality of Lake Decatur crappies, a mortality indicated by low net catches in summer, table 20. No data are available on seasonal variations in crappie foods at Lake Decatur. It is not known that high turbidity in spring seriously in- terfered with crappie feeding. On the con- trary, crappies caught in the spring of 1937 seemed to be having considerable success in capturing gizzard shad. The reason for late-summer loss of con- dition in small crappies remains as obscure as the reason for their condition loss in the spring. AGE AND GROWTH The uses to which growth data on fish may be put depends in large measure on the accuracy of age determinations. In many instances, annual rings on the scales of white crappies appear to give only ap- proximations of age, and the practical ap- plication of the scale method of age deter- mination in these fish has been limited in Illinois mainly to detection of stunted populations. Age Determination Evidence was obtained at Lake Decatur during studies on date of annulus forma- tion in white crappies that the age rings, fig. 9, are not invariably formed at the rate of one ring for each year of life nor at exactly the same time of j'ear. This evi- dence may be summarized as follows : \. In 1935 and 1937 some individuals failed to form annual rings because they did not grow in those years. While the observed cases of failure to form these rings appeared to include only a small proportion of the total population, there seemed to be a possibility that the percent- age of cases was high in certain broods. 2. In the collection of September, 1937, 65 per cent of the members of the 1'136 brood had two annuli, one of which was necessarily false. The false annulus, or the one thought to be false, while com- paratively inconspicuous in some individ- uals, was well defined in otiiers ; some an- nuli showed cutting-over similar to that shown in fig. 9 and in other respects bore a close resemblance to the rings ordinarily considered to be true year marks. 3. In many scales collected at Lake De- catur the first annulus was indistinct and in some scales it was missing. Commonly the first annulus was present on some scales but absent on other scales of the same fish. A similar variation in visibility of supposedly first rings was commonly ob-. served in collections from other Illinois i localities. 4. Annulus formation occurred in dif- ferent individuals at quite different times in the spring or summer from early May to late August, table 23. The over-all period in which different fish in the popu- lation were forming annuli lasted from 6 weeks in some years to 10 weeks or longer in other years. White crappies collected during the period of annulus formation cannot be aged accurately by scale reading unless, under rather unusual circumstances as at Lake Decatur, the fish can be assigned to broods on the basis of scale patterns, fig. 10. No method has yet been discovered for determining in all cases whether mar- ginal growth represents growth of the current season or of the previous season. W^hile absorption at the edge of the white crappie scale (in summer collections) ap- parently indicates that the new year's growth has been delayed (Hansen 1937), the lack of absorption may not mean that growth of the current year has already started. Absorption seems to be of irregular and unpredictable occurrence. Summer, then, is not the most favorable time for collecting scales for age studies. From the Lake Decatur collections it appears, in spite of many exceptions, that formation of one ring for each year of life is at least usual in white crappies. But the fact that many departures from a strictly annual rate were found, and the additional fact that the scale reader would not or- dinarily be in position to detect those de- partures, tends to limit the confidence which can properly be placed in any single reading. Adding greatly to the difficulty of scale reading is the imprecise manner in which many of the rings are formed. Age determination in the white crappie is not i August, 1951 Hansi-n : Hioi.ocv of thi; Wiini; (."k.M'I'h; 245 K^^ Fig. 9.—Scale from a white crappie that measured 10.1 inches when captured from the Rock River at Lyndon, Illinois, March 14, 1931. Cutting-over is unusually conspicuous in one of the lateral fields of annulus 3. The annulus or annual ring (five annuli are shown in the scale pic- lured) is a mark separating successive zones of annual growth. It makes its appearance on the scale when the fish begins a new season of growth rather than at the termination of a season of growth. The successive dark lines between the annuli represent ridges termed circuli. The dis- tances between adjacent annuli are approximately proportional to growth increments of the fish in the years represented. The fish from which this scale was taken was not of known age, but its age is estimated to have been about 5J4 years. Its age was greater than that of most crappies taken from Illinois waters. Relatively few crappies live longer than 3 or + years. 1933 Brood 1934 Brood 1935 Brood 1933 246 Illinois Natural History Survey Bulletin Vol. 25, Art. 4 4 5 6 7 8 9 10 II 12 13 14 TOTAL LENGTH IN INCHES Fig. 11.—Length-frequency distribution (by half-inch classes) of Lake Decatur white crap- pies collected during the period 1935-1940. (Data from table 19. Some seasons omitted from graph because of meager data.) '9 August, 1951 Hansen: Bioi.oov of the \Vhitk Craimmi; 247 tew cases of age approximation did the age read deviate from the true age by more than a \ear. Few scales were discarded for lack of their easy readability. If. on an individual scale, a ring was present that was believed to be false, the ring was omitted from the count. Conversely, a ring was sometimes counted, though imperfectly shown, or even entirely lacking, if supplementary in- formation, such as length of fish, indicated that it should have been present. How- ever, no addition was made to the count in the case of an unformed ring of the current >ear in a fish collected within the period of annulus formation. The lack of a thoroughgoing study of age reading in crappies of positi\ ely known ages means that it is not yet possible to judge the success with which ages usually have been puzzled out or to appraise the eftect of errors introduced either by faulty ring formation or faulty scale reading. The Lake Decatur white crappie scales studied intensiveh for se\eral vears were usuall.\' more easily understood and prob- ably read with a greater degree of ac- curacy than the scales from other places in the state. Favoring accurate determina- tions in the Lake Decatur scales uerc wide thictuations in annual growth, which pu>duced ring spacing patterns that were generally diagnostic for the various broods. Fig. 10 shows these patterns in three brt)ods. Two later broods were separated on a length basis. Size and Age Distribution The size distribution in net catches of white crappies at Lake Decatur changed considerably from year to year, table I'' and fig. 1 1. Catclies in some years included many large crappies ; in other years mostly small. Moderate to large sizes, 8 to 1 1 inches, were prevalent in the nets at two periods (in alternate years) during the 4 years of stud\ : from the fall of 1^)36 to the summer of I'^J? and from the fall of 1038 to the spring of 1939. Occasional Table 19.—Leniith distribution of white crappies caught in hoop nets at Lake Decatur; col- lections are grouped according to .Vmonth periods—spring: March, April, May; summer: June, July, August; fall: September, October, November; and winter: December, January, February. The same data expressed as percentages are plotted in fig. 11. TOTA L Length, Inches* b 4 4^... 5 SJ^... 6 6H... 7 VA . 8 m.. 9 10 II 12.. 12H . 13 13^... 14 Tola/ 2 9 8 11 18 12 7 3 3 3 78 3 17 78 65 29 S3 41 52 40 10 19 9 4 3 3 428 1 4 7 25 47 26 18 30 17 12 2 4 2 2 197 2 1 1 2 12 14 40 45 39 80 44 36 9 1 336 1 8 22 66 66 57 148 22 4 294 1 2 2 17 28 40 70 101 117 55 17 2 1 1 454 6 9 18 17 16 16 24 58 57 122 95 59 21 9 4 4 4 2 541 9 70 125 121 35 10 3 4 4 I 3 1 388 to t-- u. ro 18 1 I 1 22 79 67 51 25 14 8 3 7 II 7 9 320 ^0^ 3 12 21 22 20 16 9 3 2 2 116 1 3 5 19 23 18 15 10 12 11 11 1 8 4 2 143 UJ OO 153 1 6 12 15 13 21 44 77 106 93 67 45 25 7 7 15 16 7 2 579 W ON 1 33 135 225 54 43 33 20 21 24 7 5 4 I 1 2 6 4 619 3 2 1 27 83 90 39 7 3 3 4 2 \ 266 o U ON 1 1 3 58 260 298 102 40 11 11 17 7 4 4 817 ' Clajs center; for example, the 6-inch class includes fish of 5.8 thrniigrh 6.2 inches in length. 248 Illinois Natur.^^l History Survey Bulletin Vol. 25, Art. 4 observations of fishermen's stringers showed that nets were good indicators of the sizes likely to be caught by anglers. Changes in Size Distribution. — Three separate factors enter into the changes in size distribution in the net samples : ( 1 ) availability in summer of broods hatched in the previous year; (2) summer growth of individual fish; and (3) periodic large-scale, and somewhat sud- den, natural mortality of large fish, leav- ing for a time mainly fish of small sizes. The removal of large crappies by anglers is believed to have been a minor factor contributing to the periodic scarcity of large fish in the net samples. Conspicuous changes in size distribution ' in white crappie populations were ob- served by Thompson & Bennett (1938) in an Illinois lake and by VVickliff cl al. (1944, 1946) in severalOhio lakes. Size distribution changes in a black crappie population were observed by Thompson ( 1941 ). Thompson suggested that a single successful brood of black crappies hatched at Senachwine Lake in 1 year was able to consume most of the young crappies hatched for 3 or 4 years thereafter. When this first brood reached an age of 4 or 5 years, its members were sufficiently re- duced by mortality that another brood survived in abundance. There is no evi- Table 20.—Number of white crappies of various broods taken in hoop-net catches and number caught per net-day at Lake Decatur. August, 1951 Hansen: Biology of the White Crappie 249 dence that one brood dominated later broods in this manner at Lake Decatur, where strong broods were produced each year. Changes in Age Distribution.— The entry of \oung broods into the net samples and the droppin .7 - '^ - - oCo^::::' — . —.—.< V, —1^ • >. - ^ ^ ._,_', -, c . to ^ tl »^ ^ w t,SCO ^5 S fr •X c " SP 258 Illinois Natural History Survey Bulletin O •C August, 1951 Hansen: Biology of the White Crappie 259 Fig. 13.— Illinois localities represented by age determinations of fish included in table 28. 260 Illinois Natural History Survey Bulletin Vol. 25, Art. In Illinois waters other than Lake De- catur, study of growth in fish more than a year old was based on' scale samples from lakes or streams in 33 localities in widely scattered sections of the state, fig. 13. Lengths of fish having a like number of annual rings were averaged for each collecting period at each locality, table 28. Table 28 shows wide differences in sizes of fish having a like number of an- nual rings. Some of these averages are not subject to direct comparison, since small fish in the samples were not always adequately represented. Especially was this true in several samples collected in 1931 and before (footnote 3, table 28). Some collections were made during the active growing period of the fish collected, while others were made between grow- ing periods. In the case of summer col- lections, it was not known whether the outer ring on a scale was the ring of the current year or of the preceding year. Data on some of the outstanding ex- amples of white crappie populations con- taining fast-growing and slow-growing fish are recorded in table 29. Popula- tions containing slow-growing fish like those found in Weldon Springs, Lincoln, and Homewood lakes are termed "stunt- ed." Such populations contain only a small percentage of crappies over 8 inches in length even though a large percentage are 3 to 5 years old. Growth in these populations is not so abnormally slow dur- ing the first 2 years as during the third year and later. Of all Illinois waters sampled. Horse- shoe Lake, in Alexander County, con- tained the largest white crappies. In this lake, annual growth increments were es- pecially large among fish that had lived beyond the third year. Also, the rate of survival of fish beyond the fourth year ap- pears to have been exceptionally high. The Horseshoe Lake population has been analyzed previously by Thompson & Ben- nett (1938). Probably the good growth observed in this lake was due to the recent origin of the population. The lake was drained in 1930 and refilled and restocked in 193L Lake Decatur, where growth was rapid, and Homewood, where growth was slow, table 29, are in the same central Illinois locality ; Homewood Lake was formed by damming one of the small valle\s tribu tary to Lake Decatur. Growth Rates in Out-of-Stat{ Waters.—Growth of tiie white crappi( has been studied in three neighboring states : at Reelfoot Lake, Tennessee, In Schoffman ( 1 940 ) ; at Lake of thi Ozarks, Missouri, by Weyer (1940); ir Indiana lakes by Ricker & Lagler (1942) and Johnson (1945) ; and in three TVA reservoirs, two in Tennessee and one ir North Carolina, by Stroud (1949). Tlu growth rates observed in these bodies ol water fall approximately in the range ob served in Illinois waters. Eschmeyer & Jones (1941) found that in the early years of impoundment ol Norris Reservoir, the black crappies there grew at a much faster rate than has yel been observed in Illinois white crappies The first brood of black crappies hatchec in Norris Reservoir (in 1937) averaged 11.5 inches (total length) when they hat completed two summers of growth. (Thi best recorded growth for an adequate sample of Illinois white crappies with tw( completed summers was found at Lake De- catur in the winter collections of 1936-37 The fish of these collections averaged B.t inches in length.) The third brood ot black crappies hatched at Norris Reser voir (in 1939) grew at about the same rate in their first summer as Illinois white crappies of the same age, but the rate of growth in their second year, when the\ reached 8.9 inches, was faster than the best average for Lake Decatur. Eschmeyer & Jones (1941) attributed the good growth in the early years at Norris Reservoir to abnormal richness oi the lake in basic food elements and lack of severe competition. SUMMARY This paper is based primarily on an intensive study of the white crappie in Lake Decatur, Macon County, Illinois, where sampling was carried on at 1- to 2- month intervals the year round from late 1935 to late 1939. It is based in part on, additional information obtained from var- ious fisheries investigations carried on by members of the aquatic biology staff of the Natural History Survey during an 18-year period beginning in 1927. ugust, 1951 Hanskn: Biology of the White Crai'pie 261 The white crappie and the black crap- ie, both important as sport rislics in lUi- ois. are abundant throughout the state. "he white crappie generally outnumbers le black in small streams or creeks and 1 artificial lakes of all sizes. The black •nds to be the more common species in le deep glacial lakes of northeastern Illi- i)is. In the larger ri\ers and in the bot- >mland lakes preponderance of one )ecies over the other varies from lake to ike and from one part of the channel to lother. At the time of this study, fishermen used irious methods of angling, some uncom- lon, and various kinds of baits in fishing )r white crappies in Illinois. At Lake )ecatur they caught white crappies prin- pall\ from .March 1 to June 1. In year-round hoop-net fishing at Lake •ecatur, the poorest catches were made 1 the summer. White crappies require 2 years or, )metimes, 3 years to reach sexual matu- ty. The smallest ripe female obser\ed I Illinois measured 5.6 inches total •ngth. Dark breeding coloration was lund in most males of breeding size from ipril to June (or July I and was seen in ne female. Ripe females (with mature ;gs) were found in Illinois as early as lay 6 and as late as July 13; ripe males > early as May 16 and as late as June +. The height of the Illinois spawning •ason is probably late May or early June. t appears that only a portion of the eggs 1 ripe females are laid and that perhaps considerable number of unlaid eggs are Jsorbed. Crappies spawn under a variety of jnditions of bottom, water depth, and roximity to vegetation, embankments, nd wooden structures. They seem to low a preference for depositing their eggs n plant material, but they do not require luatic plants for that purpose. Net samples showed a predominance f males among young white crappies, a redominance of feinales among older hite crappies. They showed a temporary rarcity of males in late spring and early imnier. Lymphocystis. the most common disease bserved in white crappies. was found in ^5 per cent of the white crappies in one Kalitv. Comparisons in the rclati\e plumpness of the members of different length classes and broods were based on the coefficient of condition, K. Small fish usually began their annual growth before large fish and showed earlier summer gains in condition. Large fish reached peak condition in late fall or earl\ winter ; small fish reached peak condition in midsummer. Small fish showed condition losses in late summer and ad- ditional losses in early spring. Large fish suffered condition losses mainly in spring and early summer. At most times of the year the K \ alucs were higher in large white crappies than in small ones. Differences in K values were least apparent in June and July when the large fish were at the low point in the condition cycle and the small fish were nearing the top of the cycle. K values were approximately the same in males and females of the same size cate- gories, irrespective of time of year. Evidence obtained at Lake Decatur in- dicates that the annual rings on the scales of white crappies are not invariably formed at the rate of one ring for each year of life and that the rings are not formed at exactly the same time of year. The sizes of white crappies caught in the nets at Lake Decatur fluctuated strongly from year to year. Large sizes were abundant only in alternate years. Disappearance of large sizes is believed to have been due to large-scale summer mortality (heavier some summers than others). Lake Decatur crappie broods were generally short lived. Broods were usualK not conspicuous in net catches beyond the second or third year of life. One brood disappeared completely at the age of 3 \ears and 3 months; another brood at 4 years and 4 months. Dates of annulus formation were ob- tained for 4 consecutive years at Lake Decatur. Start of growth ranged from earh' May in some fish to late August or later in others. The annual growth period at Lake Decatur varied for most individual fish from about 2 to 6 months. Some individ- uals failed to grow at all in 1935 and 1937. The axerage observed lengths of white crappies falling into various annual ring classes were recorded for Lake Decatur 262 Illinois Natural History Survey Bulletin Vol. 25, Art. and a otiier Illinois localities. The an- nual growth increments of the white crap- pies at Lake Decatur varied widely from year to year. This was true particularly of fish in the second and third years of life, which grew exceptionalh well in 1936 bu made little or no growth in 1935 and 193/ Only small differences in the growt rates of males and females were foun among the white crappies of Lake Decatui LITERATURE CITED .lonymous 1919. Crappie spawn in Washington Aquariiiiii. A0. Harper, D. C. 1938. Crappie and calico bass culture in Texas. Prog. Fish Cult. 38:12-4. Hile. Ralph 1931. The rate of grovvth of fishes of Indiana. Ind. Dept. Cons. Dtv. Fish and Game. Invesi Ind. Lakes 1(2): 8-55. Hubbs, Carl L., and Gerald P. Cooper 1935. Age and growth of the long-eared and the green sunfishes in Michigan. Mich. Acad Sci., Arts and Letters, Papers 20:669-96. Hubbs, Carl L., and Karl F. Lagler 1947. Fishes of the Great Lakes region. Cranbrook Inst. Sci. Bui. 26. li;6 pp. James, Marian F. 1946. Histology of gonadal changes in the bluegill, Lepomis macroclilrus Rafinesque, and xh largemouth bass. Hum salmoides (Lacepede). Jour. Morph. 79(1): 63-86. Johnson, Wendell L. 1945. Age and growth of the black and white crappies of Greenwood Lake, Indiana. Ind Dept. Cons. Div. Fish and Game and Ind. Univ. Dept. Zool. Invest. Ind. Lakes am Streams 2(15) :297-324. Jones, Alden M. 1941. The length of the growing season of largemouth and smallmouth black bass in Norri Reservoir, Tennessee. Am. Fisheries Soc. Trans. 70:183—7. Luce, Wilbur M. 1933. A survey of the fishery of the Kaskaskia River. 111. Nat. Hist. Surv. Bui. 20(2) : 71-12.1 Miller, Lawrence F., and Paul Bryan 1947. The harvesting of crappie and white bass in Wheeler Reservoir, Alabama. Tenn. Acad Sci. Jour. 22(1) : 62-9. Mottley, Charles McC. 1938. [ 03S of weight by rainbow trout at spawning lime. Am. Fisheries Soc. Trans. 67:207-10 Nelson, T. F. 1941. Fertilizing bass ponds. Prog. Fish Cult. 56:28-9. Nigrelli, Ross F., and G. M. Smith 1939. Studies on lymphocystis disease in the orange filefish, Ceratitcnnllius sclioepfii (Wal baum), from Sandy Hook Bay, N. J. Zoologica 24(2) :255-64. Pearse, A. S. 1919. Habits of the black crappie in inland lakes of Wisconsin. IT. S. Commr. Fisheries Kepi for 1918 (.-Vpp. 3). Bur. Fisheries Doc. 867. 16 pp. Richardson, R. E. 1913. Observations on the breeding habits of fishes at Havana, Illinois, 1910 and 1911. Ill State Lab. Nat. Hist. Bui. 9:405-16. k Ricker, William E., and Karl F. Lajjler 1942. The growth of spiny-rayed fishes in Foots Pond. Ind. Dept. Cons. Div. Fish and GanK and Ind. Univ. Dept. Zool. Invest. Ind. Lakes and Streams 2(5) : 85—97. Russell, E. S. 1914. Report on market measurements in relation to the English haddock fishery during th( years 1909-1911. ( CJt. Brit.) Min. Ag. and Fisheries Fishery Invest. Ser. 2, S(l):l-76 Schoffman, Robert J. 1938. .'Vge and growth of the blue-gills and the largemouth black bass in Reelfoot Lake. Reel foot Lake Biol. Sta. Rep. 2:5-27. 1939. Age and growth of the red-eared sunfish in Reelfoot Lake. Reelfoot Lake Biol. Sta Rep. 3:61-71. 1940. Age and growth of the black and white crappie, the warmouth bass, and the yello« bass in Reelfoot Lake. Reelfoot Lake Biol. Sta. Rep. 4:22-42. i\ugust, 1951 Hansen: Biology of the Wihth C'raimmk 265 ttroud, Richard H. IMS. Circiwih of the basses and black ciappie in Noiris Reservoir, Tennessee. Tenn. Acail. Sci. Jour. 23(1) :31-99. 1949. Rate of growth ami condition of game and pan tish in Cherokee anVeyer, Albert E. 1940. The Lake of the Ozarks. A problem in fishery management. Prog. Fish Cult. 51:1-1(1. A'ickliff, E. L., Mark White, Georije Messerly, Jack Kodehautih, Lee Roach, Elwood Seaman, , and C. S. .\laclntire 1944. Ten year summary of (ish management activities for (he Muskingum watersheil con- servancy district lakes. Ohio Div. Cons. Bui. 171. 50 pp. 1946. 1945 Supplement to the ten year summary of fish management aclivities for the Mus- kingiuii watershed conservancy ilistrict lakes. Ohio Div, Cons. Supplement to Hul. 171. 6 pp. Recent Publications ^ A.—ILLINOIS NATURAL HISTORY SURVEY BULLETIN. Volume 22, Article 1.—The Plant Bugs, or Miridae, of Illinois. By Harry H. September, 1941. 234 pp., frontis. + 181 figs., bibliog., index. $1.25. Volume 22, Article 2.—Studies of North American Plecoptera, with special reference the fauna of Illinois. By T. H. Prison. September, 1942. 122 pp., frontis. + 126 fig bibliog., index. $1.00. Volume 23, Article 1.—The Caddis Flies, or Trichoptera, of Illinois. By Herbert Ross. August, 1944. 326 pp., frontis. + 961 figs., bibliog., index. $1.50. Volume 23, Article 3.—Overfishing in a Small Artificial Lake: Onized Lake near Alton, Illinois, By George W. Bennett. May, 1945. 34 pp., frontis. + IS figs., bibliog. Volume 24, Article 1.—^The Mosquitoes of Illinois (Diptera, Culicidae). By Herbert H. Ross. August, 1947. 96 pp., frontis. + 184 figs., bibliog. 50 cents. Volume 24, Article 2.—^The Leafhoppers, or Cicadellidae, of Illinois (Eurymelinae- Balcluthinae). By D. M. DeLong. June, 1948. 280 pp., frontis. + 514 figs., bibliog., index. $1.25. Volume 24, Article 3.—The Bass-Bluegill Combination in a Small Artificial Lake. By George W. Bennett. December, 1948. 36 pp., frontis. + 10 figs. Volume 24, Article 4.—The Pseudoscorpions of Illinois. By C. Clayton Hoff. June, 1949. 86 pp., frontis. + 51 figs., bibliog., index. 50 cents. Volume 25, Article 1.—Characteristics of Residual Insecticides Toxic to the House Fly. By Willis N. Bruce. July, 1949. 32 pp., frontis. + 14 figs., bibliog. Volume 25, Article 2.—Effect of Permanent Flooding in a River-Bottom Timber Area. By Lee E. Yeager. August, 1949. 32 pp., frontis. + 21 figs., bibliog. Volume 25, Article 3.—Canada Geese of the Mississippi Flyway, with special reference to an Illinois flock. By Harold C. Hanson and Robert H. Smith. March, 1950. 144 pp., frontis. + 82 figs., bibliog. B.—ILLINOIS NATURAL HISTORY SURVEY CIRCULAR. 36.—Planting and Care of Shade Trees. By J. E. Davis. September, 1947, (Third a printing, with additions.) 28 pp., frontis. + 20 figs. 38.—^Windbreaks for Illinois Farmsteads. By J. E. Davis. April, 1951. (Fourth printing, with revisions by L. B. Culver.) 33 pp., frontis. + 27 figs. 39.—How to Collect and Preserve Insects. By H. H. Ross. July, 1949. 59 pp., frontii., + 65 figs. 41.—How to Recognize and Control Termites in Illinois. By B. G. Berger, February, 1947. (Reprinted without text revision, April, 1950.) 44 pp., frontis. + 32 figs. 42.—Bird Dogs in Sport and Conservation. By Ralph E. Yeatter. December, 1948. 64 pp., frontis. + 40 figs. 43.—Peach Insects of Illinois and Their Control. By Stewart C. Chandler. December, 1950. 63 pp., frontis. + 39 figs. 44.—The Drug Plants of Illinois. By Leo R. Tehon. July, 1951. 122 pp., frontis. + 262 figs., index. C—ILLINOIS NATURAL HISTORY SURVEY MANUAL, 2.—Fieldbook of Illinois Land Snails. By Frank Collins Baker. August, 1939. 166 pp., color frontis. + 170 figs., 8 pis. $1.00. 3.—Fieldbook of Native Illinois Shrubs. By Leo R. Tehon. December, 1942. 307 pp., 4 color pis. + 72 figs., glossary, index. $1.25. List of available publications, about 400 titles, mailed on request. Single copies of Illinois Natural History Survey publications for which no price is listed will be furnished free of charge to individuals until the Bupply becomes low, after which a nominal charge may be made. More than one copy of any free publication may be obtained without cost by educational institutions and official organizationi within the State of Illinoit; prices to others on quantity orders of these publications will be quoted upon request. Address orders and correspondence to the Chief IixiNOis Natural History Survey Natural Resources Building, Urbana, Illinois Payment preferably io the form of U.S. Post Office money order made out to State Treasurer of Illinois, SpringGeld, Illinois, must accompany requests for publications on which a pric« is let.