Bulletin ILLINOIS URB~NA STATE OF ILLINOIS DWIGHT H. GREEN, Governor DEPARTMENT OF REGISTRATION AND EDUCATION FRANK G. THOMPSON, Director NATURAL HISTORY SURVEY DIVISION THEODORE H. FRISON, Chief Volume 22 BULLETIN Management of Small Artificial Lakes Article 3 A Summary of Fisheries Investigations, 1938 - 1942 GEORGE W. BENNETT -THE RAHY O FEB o 1 UNIVERSITY Of ILUNn Printed by Authority of the State of Illinois URBANA, ILLINOIS February 1943 STATE OF ILLINOIS Dw1c;11T H. GREEN, Go'l•tr11or DEP:\RT~IENT OF REGISTRATION AND EDUCATION FRANK G. T110:"11rsoN, DirNlor BOARD OF N,\TUR,\L RESOURCES AND CONSERVATION FR.\NK G. \\'11.u.u1 TRELEASE, D.Sc., LL.D., Biology TIIO:'IIPSO!II, Clwirman EzR.\ J. KRAUS, Ph.D., D.Sc., Forrstry L. R. llowso:-:, B.S.C.E., C.E., En11i11reri11g ROGER ,\D.\MS, Ph.D., ARTIIUR Currs \V1LI.,\RD, D.Eng., LL.D., Prnidenl of the Uni'l.•rrsity of Illinois EDsoi- S. BASTIN, Ph.D., Geology D.Sc., Chemistry NATURAL HISTORY SURVEY DIVISION Urbana, Illinois SCIENTIFIC AND TECHNICAL STAFF Ttt EOOORE H. FRISON, Ph.D., Chief Section of Economic Entomology \\'. P. FLINT, B.S., Chief Entomologist C. C. Co:'IIPTON, Ph.D., Associate Entomol­ ogist l\l. D. FARRAR, Ph.D., Resrarch E11tomolo­ gist J. H. BIGGER, l\f.S., ,1 ssociatr Entomologist S. C. CHA~'DLER, B.S., Soutlzeru Field Ento­ mologist ).\MES \\'. APPLE, l\l.S., Northern Field Entomologist H. G. BERGER, l\1.A., Assistant E11tomologist 1-1. B. PETTY, JR., B.A., Assista11t, Entomol­ ogy Extension C. J. \\ 'EIN !\1.-\N, Ph.D., Research Fellow in Entomology \\' 1L1.L\M H. HASSE, Entomological Assista11t Jo11N M. \\'RIGHT, B.A., Junior Entomolo­ gist ( V. S. B. E. P. Q. and Commodity Crrdit Corporation, cooprrating) Section of Insect Survey H. H. Ross, Ph.D., Systematic Entomologist C\RI, 0. Mo11R, Ph.D., A ssoriate Entomolo­ gist, Artist (on leave) B. D. BURKS, Ph.D., Assistant Entomologist (on leave) 1\hLTON \V. SA~'OERSON, Ph.D., Assistant Entomologist KATHRYN M. SOMMERMAN, M.S., ,1rtist, Entomological Assistant Section of Forestry )AMES E. DAVIS, M.F., Extension Forestrr LEE E. YEAGER, Ph.D., Forester Section of Aquatic Hiolo!!y DAVID H. THOMPSON, Ph.D., Zoologist GEORGE \V. BENKETT, Ph.D., Limnologist D. F. HANSEN, Ph.D., Assistant Zoologist Section of Game Research and ManaJ!ement R. E. YEATTER, Ph.D., Game Specialist Section of Wildlife Experimental Areas ARTHUR S. HAWKINS, M.S., Gamr Tech­ nician (on leave) F. C. BELi.ROSE, JR., R.S., Assistant Game Teclmician J. ~-. Low, Ph.D., • .Jssistant Game TNh­ TllC/an \\'. _H_. ELDER, Ph.D., Assista11t Game Tcrlz­ ll/Clan Cooperative Wildlife Restoration ProJ!ram (State Department of Consrrvatio11 a11d V. S. Fish and Wildlife Ser'l•ire) OTTO \V. TIEMEIER, M.A., Junior Biologist Section of Applied Botany and Plant PatholoJ!y L. R. TEHON, Ph.D., Botanist D. B. CREAGER, Ph.D., Rrsearc/1 Pathologist J. C. CARTER, Ph.D., A ssista11t Botauist G. H. BoEWE, M.S., Field Botanist Section of Publications JAMES S. AYARS, B.S., Teclrnical Editor Co~sULTA~-T: Herpetology, HOWARD K. GLOYD, Ph.D., Di rut or of the .Muse urn, Chicago Academy of Sciences Tl,i., JJOJn•r i.~ a contril,utio11 from tlic Section of Aquatic lliology. (34354-3.'.\I-11-42) ~2 OBJECTIVES OF FISH MAN AGEMENT EVALUATIO~ OF FISH SPECIES Largemouth Bass .. .... . Smallmouth Bass . White Crappie . ........ . Black Crappie. Bluegill .. ...... .. . \Varmouth Bass .... . Green Sunfish . ........... ..... . Pumpkinseed Sunfish .......... . . Orange-Spotted Sunfish ...... . Yellow Perch . . . . Yellow Bass ...... ... .... . Black Bullhead .... . .... ... . Yellow Bullhead ... . ..... ....... . Speckled Bullhead .. . ... . Carp ... .. ......... .... ... . Red mouth Buffalo . ........... . Mongrel Buffalo .. ........ . Smallmouth Buffalo ....... . Gizzard Shad . ........... . Golden Shiner ...... . Other Fish . ....... . CROPPING . ... . . .. .............. ... . COX TEXTS EXPERIMENTAL COMBINATIONS OF FISH ........... . SUMMARY LITERATURE CITED . ... ....... . Page 357 358 359 361 361 362 362 362 362 362 363 363 363 363 363 363 363 36+ 36+ 36+ 36+ 36+ 36+ 365 370 376 376 Above, Illinois Natural History Survey laboratory and instrument pier on Ridge Lake, Fox Ridge State Park, near Charleston, Ill. This new 18-acre artificial lake is an experimental area for limnology and fish management studies. The laboratory is equipped for many phases of lake work and also furnishes living quarters for Survey technicians. The instrument pier, in lake at left, houses recording instruments for air and water temperatures, a rain gage, a water level recorder, and wind direction and velocity indicators. Ridge Lake, which was stocked in the spring of 1941 with largemouth bass only, was opened to public fishing in 1942. Below, the dam and outlet tower at Ridge Lake, April, 1941, when the lake was beginning to fill. The tower was designed to take care of small rises of water. The water enters the tower at its base, and, when the lake level reaches a point about 3 feet from the top of the tower, the water spills over a partition in the tower and flows through a concrete tunnel to the other side of the dam. A surface spillway (not shown in illustration) carries off flood waters. A valve at the base of the tower allows the lake to be completely drained. The face of the earth dam is shown being rip-rapped with concrete blocks to prevent washing. ... Management of Small Artificial Lakes A Summary of Fisheries Investigations, 193 8-1942 GEORGEll~ BENNETT THE management of lakes for fish­ ing should not be confused with fish culture as generally practiced in the United States. Lake management may re­ quire the products of fish culture, but its concept is much broader in that it attempts to discover and apply fundamental biologi­ cal principles and relationships associated with fishes in natural or artificial waters, with the practical object of increasing fish yields and maintaining them. "\Vhile cur­ rent literature dealing with the physical, chemical and biological aspects of fish en­ vironment is voluminous, little is known concerning the ecological interrelationships of the fishes themselves, and this field offers a great deal of promise to those investi­ gators who are called upon to find a solu­ tion to the ever increasing fishing pressure of a recreation-minded public. Artificial lakes, although often lacking some of the scenic beauty of natural \\·aters, can be made attractive as centers of recreation throughout much of our country. From the standpoint of fish man­ agement, they have an advantage over natural waters in that they are usually smaller, and often can be drained or other­ wise rid of undesirable fish. However, large natural lakes as well as large arti­ ficial lakes are practically beyond the scope of the fish manager, once they become filled with undesirable fish. Large-scale netting operations on such waters may reduce the numbers of these undesirable species, but offer little assurance of perma­ nent improvement. The material in this paper includes information from several sources. That gathered by Dr. David H. Thompson, Illi- nois Natural History Survey Zoologist, and the author, from censusing the fish of 22 small artificial lakes in Illinois has been of great value in determining the kinds of fish suited to this type of habitat. It has also revealed some of the causes for poor fish yields, as well as information on the compatibility of various species. Angling records supplemented by hoopnet samples from several lakes provide a means of measuring the effects of underfishing and overfishing on fish populations. The case histories of many experimental lakes in which various combinations of fishes have been stocked suggest the degree of useful­ ness of the different combinations in fish management. Objectives of Fish Management The primary objective of fish manage­ ment is to produce and maintain "good fishing." A definition of "good fishing" should include the element of numbers of fish caught per unit of time or effort, as ,nll as that of size of individual fish. Numbers and sizes can hardh· he defined satisfactorily for all cases, bec;use of vari­ ation in the kinds of fish involved as well as in desires of the fishermen. However, the fish manager has need of some criterion useful (although not entirely satisfactory) in comparing the "goodness" of fishing waters. There is some agreement on the criterion of numbers place-cl at one fish per man-hour. In Illinois, where nearl r all catches are bass, crappies, sunfish ( cen­ trarchids) or catfish, \\·e ha,·e defined "de­ sirable size" for several common species ( Bennett, Thompson & Parr 19+0, p. 3). [ 357 J 358 I LLl;\OIS ~ .•\TL R.-\L H I STO RY S U R\"EY R ULI.ETI:-- /'al. 22, ,/rt . 3 Thi~ rrpre~ents :-ipproximately the mi ni­ mum ~izr for tahlr use. For e:x:-i mple, in the hlue!,!ill this minimum has been set at 6 inches total length or about 0.25 pou nd ; in the crappie. 8 inches or abou t 0.30 pound. A suggested definition of a good tishing lake is one which produces an anr­ a(l'e c:1tch of one fish of desirable size per 11~111-hour of effort during the fishing sea­ son. and one which will maintain this rate n-ar after ,·ear. Swingle & Smith ( 1938 ) in their J f111agr111r11/ of Farm Fish Ponds and in other puhlications (1939, 19+ 1, 194-2) say little about mainta in ing sus­ tained ,·ields, except through per iodic draining. and restocking. The fish manager should have some knowledge of the carrying capacit ies of his lakes, and the kinds of fish that are present . a, well as the intensi t r of fish ing pressure. He can assume thro~gh experience some reasonable poundage figu re ( based on nor­ mal increment of the fish and carrying capacity of the lake) for cropping each h:ke, to sen·e as a guide in the yearly har­ vest of fish. O nly by cont rolling the fish­ ing pressure within a mi nimum range around the actual optimum yield can he have any assurance of sustained good fish­ ing. ~ Ioreo\"er, he should have the ability not only to recognize, but to control , cer­ t:-iin outside influences which mar limit or upset his planned yield. For ex;mple, the introduction of rough fish, such as carp and huffalo, through use of ha it minnows ma,· in time so restrict the size and abun­ da~ce of hook-and-l ine species as greatly to reduce the yearh· catch. The import~nce ·of rough fish in limiting good fishing in art ificial lakes has often been underestimated or on rl ooked. \ Vhen carp or huffalo gain en t rance into these lakes, they greatly influence the success of more desirable kinds. A change in the status of the game-fish populat ion may come about through disturbance during the spawning period of the nest-huild ing fishes, or rough fish may cause ( through greatly increased turhidity) such a modifica t ion of the em·ironment that it hecomes unsuitable to the game and pan fish. Roilr art ificial lakes in Illinois invariabh· contai n manr rough fish or hullheads and small numhe;s of stunted crappies and sunfish. In la kes containing large populations of rough fish, additional stocking of centrarchids will not impro\·e fishing. \Vhen the rough fis h are enti reh removed, the lakes become clear, and there is a marked impro\"ement in size, condit ion and numbers of the game-fish population. In some waters poor fishing mar be due to an ab undance of so-called forage fish , those species that are popularly supposed to sen·e as fond for the desirahle game fish. H ow these limit the numbers of more de­ sirable fi sh is unknown , but crowding and food competition may be important factors. Popular misconceptions have led l llinois fish ermen or their organizations to insist upon th e introduction into artificial lakes of several species of valuable fishes that are not suited to this environment. The most common fi shes of this classification are the smallmouth bass and white bass. Other important fi shes somewhat less common}~ stocked are the walleyed-pike, northern pike, lake trout and muskellunge-the lake fishes of the north. The warm water and low oxygen concentrations seasonally char­ acteristic of artificial lakes insure the earh· death of such fish. In a few instances i;1 \\·hich they managed to survi\·e for a time, they were unable to reproduce successfully. There are , howe,·er , a few species of warm water fish apparently well suited to artificial lakes; these include largemouth bass, crappies, bluegills and bullheads. Up­ on these the l llinois lake fisherman must depend for angling. Yet problems arise " ·hen these fish are used, because of their great reproductive potential and the lack of natural predators. Stunting is the most common cause for poor fi shing in artificial lakes stocked with these species. Although the largemouth bass is the most predatory of these fish, it seems unable to control populations of bluegills and crappies with­ out the assistance of heavy hook-and-line fi shing. Evaluation of Species More than +O species of fish were found in 22 artificial lakes of Illinois in the course of censusing their fish populations. \Vhile most of these lakes furnished little or no fi shing for a time previous to renova­ tion, several represented average fishing waters, and a few were producing excel­ lent catches. Past yield and stocking records are vague for many of these lakes. Such information may be gathered from lake owners or fishermen, but at best it is F ebruary, 19./-3 BENNETT : ~ l ANAGE:\IENT OF ARTIFICIAL LAKES 359 some"·hat inaccurate. In a few instances the censuses correlated niceh · ,Yith verbal historical information. U su~ll \', however, the older waters had been stocked so many times , and from so many sources, th at it "·as impossible to determine the origi n of their fish. In a few instances this historical information indicated that u nfavorable changes in fishing had taken pl ace w ith in the past 5 or 6 years; earlier these lakes had produced good fishing, but grad ually had changed until they produced littl e or none. A perusal of fi sh censuses of the 22 lakes gives information not only as to what spe­ cies do well in artificial lakes but also something of their potential ,·alue in fish management. For example , if g reen sun ­ fish, L epomis C)'anellus Rafin esque, w ere found in nearly all lakes, but neve r of size-; large enough to interest fisherm en , it might be conceded that stocking thi s fi sh in other artificial lakes would offer little in return for the effort . \ Vith the purpose of mak­ ing a rough eval 11ation of common fi shes, the censuses were careful h · studied. Tables 1 and 2 present a par t ial sum­ mar\' of these lake censuses. Table 1 lists the lakes and ponds with the composition of their fi sh populations for more common species given as per cents of total weight of fish. Table 2 lists the same lakes and ponds with their locations, areas, types of basin s, transparencies in feet at th e time their fish populations "·ere removed, and the total poundage of fish removed per acre. The status of the more important species could have been expressed in tabl e 1 as per cents of the total populations by num­ bers instead of by weights, but it is felt that the use of weights rather than num­ bers gives a better indication of the im­ portance of indi vidual species. The designation of "old " and " new" under types of basins in table 2 is as fol­ lows : " I'\ ew" lakes and ponds a re less than 5 j·ears old , while "old " are from 5 to 50 years. The tran sparencies listed in the next column are only rel ati ve, as con­ siderable variation may · be fo und du ring any year. However , it may be seen that there is some correlation between lo,Y transparencies given in t able 2, and high percentages of carp , buffalo, bullheads and gizzard shad, listed in t abl e 1. The column "Total \Veight of Fish, P ounds per Acre," table 2, is the result of dividing the total poundage of fish taken from the lake by its surface area in acres. It will be noted that the older waters usually sup­ port the higher poundages of fish and that lakes containing large percentages of rough and forage fish show greater poundages than those containing mostlr desirable fish. In the following paragr~phs, important species are considered separateh· and on the basis of the census work ontli~ed in tables I and 2. The status of each species was dete rmined in each lake where it occurred, and each species was considered in relation to other species present. The arrangement of t hese fish in the fo ll owing paragraphs is not systemat ic. Largemouth Bass Huro salm oides (Lacepede) Con t rary to general belief, the large­ mouth bass does not require a habitat of large size. It was foun d in 18 of the 22 Illin ois lakes censused, and the hass popu­ lations averaged better in small than in large lakes, both in numbers and in size of individuals. P opul ation densities varied fr om a fractio n to 129 fish per acre of water. In five lakes, the bass population made up from I+ to 25 per cent of the w eight of the total fish population. Only one of th ese five lakes contained more than a very few rough fish. Forage fish were present in only one of the three lakes con­ tain ing the highest percentages of bass. Bass made up 25 per cent of the total population ( by weight) in a lake that was overfished. Here angl ing was restricted du ri ng the spawning season, hut intensi\·e at other t imes. In the 13 other lakes in which they were found, bass were less numerous. By weight they represented less than + per cent of the fish populations. All of these lakes contained large poundages of rough fish and forage fish ( gizzard shad, golden shiners and other minnows) and all hut three contained large populations of crap­ pies. ~lost of these lakes "·ere muddy throughout the year. . Successful largemouth bass populat1orb were found in clear water. Repeated stocking of bass in muddy lakes ~ont:1ini~1g large numbers of rough. fish did not Ill­ crease the bass populat10n permanently. Small bass populations are frequently asso- To hie 1.-Cornposition of the fish populations of the Jokes listed in tahle 2; for each important species of fish is reco rded its per cent hy wei~ht of 5:'. the total fish population of each hike. o B ODY OF \\ 0 ,\TER :c E-- :: ~"' t.i"' c.:; < ~ :c :c ... ..J ~"' ..I"' ..: < ==::i:: en t.i t.i ~ !-- c(, iu :;,.... ,,,. t.i c.. c.. ~ < u c(, ::jU 0:: ....l ..I G t.i ::, ..I 0:: :c ... ::, 0 :,i :; VJ c(, < .< :xi ::::: :c !" ~ ; (.,.., February, 1943 BENNETT: MANAGEMENT OF ARTIFICIAL LAKES 361 Table 2.-A summary of the fish censuses of 22 artificial lakes in Illinois, showing lake areas, types of basin, transparency of· water, and total poundages of fish collected per acre. ToTAL SURFACE Type TRANS PAR- WEIGHT BODY OF WATER LOCATION AREA, OF ENCY, OF FISH, ACRES BASIN IN FEET* PouNDs PER ACRE Weldon Springs Lake _ .. _ Near Clinton ____ 12 . 10 Old reservoir __ . - 409 Southside Country Club Lake . __ ._._._ ........ Near Decatur .... 8.40 Old reservoir. _ . - 719 Lower Twin Lake ... __ . _ Near Decatur .. __ 1.36 Old pond ...... 1.7 778 Homewood Lake .. _ . _ . _ . Decatur _ ........ 2 .83 Old pond __ . _ . _ 1.5 699 Fork Lake ._ .. _._ ..... _. Near Mount Zion 1.38 Old pond ...... 0 .6 539 Farmer City Golf Course Lake .. ____ ._._ .. ___ ._ Farmer City .. __ . o_ 75 Old pond ...... 1.2 455 Edwards Pond _ .... _ .... Near Kincaid _ ... 1.00 Old pond __ . _ . _ 1.0 398 Upper Twin Lake ___ . _ . _ Near Decatur _ ... 1.08 Old pond ...... 0 .5 392 Crystal Lake Club No. 1 Illinois, near Bur- Lake ... _ .. - - . - ..... - - lington, Iowa . .. 0 .75 Old pond ..... - 358 Black Jack Lake ___ ..... Illinois, near Bur- lington, Iowa_ .. 4.00 Old pond __ . _ . _ - 280 Delta Pond _ ............ Jonesboro ... _ ... 0 .80 New pond .. _ .. 4 .0 234 Kline's Lake .. _ .. ____ ... Near Le Roy . . _ .. 1.30 New pond ._ ... 2.0 230 Jack's Lake ._. ___ ....... Near Decatur .... 1.50 New pond ..... 2.3 221 Shell Lake .............. Near Clinton .... 1.50 Old pond ._ .... 0 .7 215 Onized Lake ............ Near Alton ...... 2 . 14 Old pond ... : .. 2 .5 206 W altonian Pond ___ .. _ ... Near Rudemont .. 1.10 New pond m forest land .. _ 3.0 71 Buck's Pond ............ Near Monticello .. 8 .60 Old oxbow . _ ... 0 .5 1,145 Crystal Lake .. __ ....... _ Urbana .......... 6 .30 Old oxbow __ ... 0 .8 658 Duck Pond, Pollywog Association ........... Near Oakwood .. 3 . 10 Old strip mine . 2 .2 673 Triangle Pond, Pollywog Association ........... Near Oakwood .• 2 .50 Old strip mine .. 2 .1 487 Duck Island Farm Lake . Near Banner ..... 4 .90 New gravel pit . 1.5 316 Sportsmen's Lake ....... Near Lincoln .... 3 .70 Old gravel pit .. 3.0 341 Average ..... . ...... ··············· .. 3 . 23 1. 73 446 .5 • Secchi disc transpa r ency at time of r enovation. ciated with large crappie populations and vice versa, as crappies seem to be the main competitors of bass. Smallmouth Bass Micropterus dolomieu Lacepede The smallmouth bass is not suited to artificial lakes that depend on surface drainage for water supply. It was present in only 3 of the 22 lakes censused, al­ though it had been stocked in others. One lake contained only two specimens, both of legal size. Another lake of 1.3 acres contained 21 of these fish, the largest weighing 1.25 pounds; a few small ones were collected, indicating partial spawn­ ing success. Associated with these small­ mouth bass in the 1.3-acre lake were small bullheads, green sunfish and more than 8,500 blunt-nosed minnows. The smallmouth is common in most Illinois streams and is frequently stocked in artificial lakes from this source. Almost without exception, the species of fish seined from small swift rivers are worthless for stocking lakes, either because they cannot tolerate lake conditions, or because they are of little value in angling. A few small­ mouth bass, as well as several spotted bass, were taken from a strip-mine pond in Ver­ milion County that had been flooded by an adjacent stream. White Crappie Pomoxis annularis Rafinesque The white crappie was present in 17 of the 22 lakes, and in one lake constituted 38 per cent of the total fish population. This species is well suited to artificial lakes and reproduces very successfully. In 13 362 l 1.1.1:-.01s :'\ ,, TU R.-\1. H1 s TORY SuR,·Ey Bu1.1.ET1:-. /"ol. 22 .• -/rt. J of the 1 7 lakes the white crappies were stun ted. Fou rteen of the lakes contained black crappies as well as white. 1 n all but two, the w hite cra ppies were more numer­ ous. In one la ke where the white crappies were of good size ( and amounted to 28 pt·r cen t of the weight of the population), thn \\·ere associated with largemouth bass, wa~mouth hass and bluegills. The most pronou nced stunting of white crappies oc­ curred in shallow mudd,· lakes, where the,· were associated with. large numbers ot ·rough fish. In general, white crappies do well with other centrarchids, but must he thinned at frequent intervals to prevent stunting. Black Crappie Pomoxis nigro-maculat us ( Le Sueur) Al though black crappies were present in 1 7 of the 22 lakes, ther were usually less numerous than the \\·hite and of larger a\'crage size. Stunting was common, due to overpopulation and to competition with rough fish. Reproduction in the black crappie seems to be somewhat less success­ ful than in the white. In the overfished lake mentioned in connection with the largemouth bass, the population of black crappies had been greatly reduced in num­ her lw two seasons of intensive hook-and­ line fi shing. In an underfished lake, a hadl r stunted population of black crappies made up nearly 25 per cent of the total population. Here they were associated w ith white crappies, bluegills, green sun­ fi sh and bullheads. In the lake containing the second largest population of black crappies, this species represented only about 6 per cent of the total weight of fish, and in other lakes it constituted onlr a small fraction of the total popula tion"s ( -J..-J. pe r cent or less) . Bluegill L eprJ mis macrochirus Rafinesque T he blu egill is the most common as well as one uf the best fi shes for artificial lakes. I t was present in 20 of the 22 lakes cen­ sused. Associated w ith other centrarchids, it sometimes makes up as much as half of the population . It stands up under heavy fishi ng better than any other fish and pro­ duces more fish of desirable size than other sunfish . Howe\'er , because it reproduces in such tremendous numbers, underfishing al­ lows it to become stunted in manr waters. In six lakes, bluegills made up fr~m 20 to 53 per cent of the weight. Smaller per­ centages of hi uegills were associated with large populations of rough fish, forage fish and bullheads. Stunting was common un­ der these conditions. \Yarmouth Bass Clwenobryttus gulosus (Cuvier) The warmouth, present in 13 of the 22 lakes, is much less desirable than the blue­ gill. By weight it never represented more than 11 per cent of any population and usually much less. This species shows a wide range of sizes among individuals he- . longing to a single brood, a peculiarity sim­ ilar to that found in the largemouth bass. In most lakes, only a small number of fish were large enough to interest fishermen, while the greater number were small. The ratio was about one or two large fish to several hundred small ones. For all prac­ tical purposes the warmouth bass adds little to the fish populations of artificial lakes in Illinois. Green Sunfish Lepomis cyanellus Rafinesque The green sunfish, found in 21 of the 22 lakes, is the species most frequently intro­ duced into lakes from small streams. l n lakes it multiplies very successfully, but seldom produces fish of desirable size. In four ne"·ly constructed and improperly stocked lakes, it made up from 5 to 57 per cent of the fish populations. The en­ tire populations of many lakes did not include any green sunfish large enough for angling. The green sunfish must he con­ sidered detrimental in artificial lakes, be­ cause it competes with more desirable fish and usually does not reach an attractive size itself. This voracious fish remains close to shore and makes bank fishing for more desirable kinds difficult. Pumpkinseed Sunfish Lepo mis gibbosus (Linnaeus) The pumpkinseed was found in only 5 of the 22 lakes. l t was nenr numerous and rarely of good size. Although some- February, 1943 BENNETT: MANAGEMENT OF ARTIFICIAL LAKES 363 what more desirable than the green sun-· fish, it is much less so than the bluegill. Orange-Spotted Sunfish Lepo mis humilis (Girard) Although present in 9 of the 22 lakes, the orange-spotted sunfish never grows to a desirable size and should never be stocked in artificial lakes. In one recorded in­ stance, fish of this species reached an esti­ mated population of 15,000 per acre and crowded out other centrarchids. Yellow Perch Pe1-ca flavescens (Mitchill) The yellow perch, common in artificial lakes of some western states, does poorly in Illinois. In 7 of the 22 lakes censused, it was represented by a few individuals of small size. It seems unable to spawn suc­ cessfully in Illinois lakes and adds little or nothing to fishing. Yellow Bass M orone interrupta Gill The yellow bass was found in 7 of the 22 lakes. In only one instance had it re­ produced successfully. The yellow bass populations were made up of a few indi­ viduals large enough to interest panfish anglers. Because of its inability to repro­ duce successfully, and its small average size, this fish is of little value in small arti­ ficial lakes in Illinois. Black Bullhead A meiurus me/as me/as ( Rafinesque) The black bullhead was found in 20 of the 22 lakes. It is a fish well suited to arti­ ficial lakes and of importance in lake man­ agement. Large populations of stunted fish are common and often necessitate artificial thinning in order to produce bullheads of good size. In 6 of the 20 lakes, popula­ tions of black bullheads made up from 39 to 73 per cent of the weight of fish present. Bullheads of large size were found in lakes containing small numbers of these fish. The bullhead is desirable not only because it reproduces succe5sfully, but because it bites readily and is easily taken by inex­ perienced fishermen. Although it tends to keep shallow lakes and ponds roily, it will survive under unfavorable conditions long­ er than most other Illinois fish. Yell ow Bullhead A meiurus natalis natalis ( Le Sueur) The yellow bullhead, less common than the black in artificial lakes, was present in 16 of the 22 lakes censused. Populations in this species are usually much smaller than in the black. In 5 lakes it made up from 0.4 to 8.4 per cent of the total fish population; only a few were present in the other 11 lakes. Black and yellow bull­ heads are often found together, but in most lakes the blacks are more numerous. The yellow bullhead seems less likely to become overnumerous and stunted than the black species, but it is somewhat less desirable as a pan fish. Speckled Bullhead A meiurus nebu/osus marmoratus ( Le Sueur) The speckled bullhead, common in the Illinois River and connecting bottomland lakes, was taken from only 2 of the 22 artificial lakes. One of these had been recently flooded by the Illinois River, and the other had received stock from that source. This fish ordinarily does not re­ produce successfully in artificial lakes, al­ though some young were found in one instance. It grows well, but cannot be counted upon to maintain its numbers. Carp Cyprinus carpio Linnaeus Carp were found in 17 of the 22 lakes, although no records could be found that any of these lakes had been stocked with this fish. In several lakes flooded occasion­ ally by rivers, they could have entered with flood waters. Young carp are sometimes introduced through the use of live bait; and the adults swim upstream and jump the spillways into many lakes during high water. In no lake was a large carp popu­ lation found with a good game-fish popu­ lation. Always where carp were numer­ ous, the hook-and-line fish were not only small in numbers, but were small in size and in poor condition. In several lakes a small number of large carp were present. This seems to indicate that young are not I 1.1.J~OIS ;\ \TL R.-\L H ISTOR'I SUR\'EY B ULLETIX /' ol. 22, A rt. 3 prllducetl e\ er) year. or if produced do not sun·in·. Carp and buffalo arc responsible for 1111ich uf the roil\· condition of the water in artificial lak~s. as their rcmoYal i, always followed by a pronounced in­ crea:-e in transparency. H.cJmouth Buffalo .ll ,·gasf() matohus r_rprinrl la ( \7 alcn­ cienncs) Eight of the 22 lakes contained red­ mouth buffalo, constituting from 2.5 to 7 3 per cent of their total populations. These and other kinds of buffalo enter lakes on flood waters. Sometimes, how­ c, er, lakes containing these fish were some distance from ri\'crs and it is impossible to say how they had entered, unless through irresponsible stocking. .\longrel Buffalo I ctiobus niger ( Rafinesque) Ten of the 22 lakes contained this spe­ cies, although it was rareh· as numerous as the redmouth. The 1~ongrel buffalo made up from O.+ to 12 per cent of the populations containing them. Smallmouth Buffalo lctiobus bubal us ( Rafinesque) Smallmouth buffaloes were present in 6 of the 22 lakes and "·ere usually large in size. Two fish from Upper 'l\\·in Lake averaged 25 pounds each; 2-t fish a\"Crag­ ing 12.1 pounds each made up 37 per cent of the fish population of Lo,\·er Twin L ake. This buffalo is usuallv less numer­ ous than the other two, but ;11 three often are found together. The h11ffaloes should he excluded from artificial lakes, as they are rarely caught on hook-and-line and, like the carp. are associated with roilv water and poor populations of game and pan fish. Gizzanl Sha a\'eragc size of the fi sh caught and the catch per man-hour from this lake. while it was o\'erfished, with catches from se\'cral underfished ,,·aters, a striking similarity was found. I II hoth, the catch per man-hour was lo,\". I 11 hoth, a \'Cry large per cent of the fish caught were small. 1 t is little w onder that the an·rage fisherman confuses under­ fishing \\'ith oYerfishing. The relation he­ tween size and age in fishes is the hcst c riterion for judging the status of a pop­ ulation. For example, scales from 6-inch hi uegills taken from an o\'erfishcd lake show that the fish were less than 2 ,·ears old. Scales from bluegills of the sam~ size taken from u ndcrfi shcd lakes typically show from four to six annual rings. Lay­ men can often distinguish between fish from an oYerpopu latcd lake and an under­ populated lake hy the fact that those from the former are usually thin bodied, have large heads and unusually prominent eyes. Experimental Combinations of Fish The meagerness of hook-and-line fishing furnished by many unmanaged artificial lakes lca\'cs little doubt as to the ncccssitv of proper management for the productio~ and maintenance of good fish yields. The more common causes for poor yields arc summarized as follows: 1. I ndiscriminatc stocking-the intro­ duction of fish physiologically unsuited to the artificial lake habitat or those of little or no angling Yaluc. 2. U ndcsirahlc populations - those in which rough fish or other species not use­ ful in fishing make up a large part of the populations and compete with the hook­ and-line species. 3. Overpopulation - as in lakes con­ taining only desirable fish hut so densely populated that stunting resul ts, which in turn means poor fishing. All of these causes mav he controlled in small artificial lakes, o~ in large lakes that can be drained. Lakes controlled hr fishi ng clubs some­ times produce good sustained yields of fish hut, although the yearly crop and the catch per man-hour remain at satisfacton· le\'cls, there arc great Auctuations in th·c abun­ dance of the Yarious species from year to year. To fishermen who ha\'c prcf erences in fishing. these Auctuations are perhaps an annoyance. The study made hy Thompson ( ms. unpublished) of the catch records of Rinakcr Lake near Carli11Yille illustrates the extent of these Yariations. In Rinakcr Lake, where complete catch records are a\'a ilahlc from 1932 to date, the important species arc largemouth bass, white crap­ pies, bluegills and bullheads. The catch of hlucgills remained most nearly constant throughout this period of years, at 1.25 to 2.25 pounds per fisherman-day. Good catches of bass were made from 1932 through I 936, and the crappie catch was poor for these years. In 1937 the catch of crappies reached an all-time high of 2.5 pounds per fisherman-day, and the catch of hass was very low (less than 0.25 pound per fisherman-day). Since 1937 the hass catch has been steadily improving and that of crappies decreasing. Bullheads have remained at a low population level throughout all years, but individuals caught are of exceptionally large size. The total hook-and-line vield for this lake has averaged about 4 pounds per fisherman­ day and I 00 pounds per acre per year during this period. A more or less constant yield of hlue­ gills, with large fluctuations in catches of crappies, bass and bullheads, seems to he typical of lakes containing these species. Usually, however, when crappies or hull­ heads reach their peak of abundance they are not taken in sufficient numbers to pre­ vent stunting and to give bass an oppor­ tunity to make a "comehack." Fluctua­ tions· of this kind make fishing for selected species uncertain. In lakes such as Rin­ aker, the fish manager should attempt to control the size of hroods of young fish produced each year, with the object of maintaining a more nearly uniform pro­ portion among the different species. The great seasonal variation in the suc­ cess of fishing for a selected species in lakes containing many kinds of fish has led to experimentation with single species and simple combinations of more important fish. In the stocking of many new ponds and several large reservoirs in Illinois, an attempt is being made to discover some means of maintaining good bass fishing. The comhination of largemouth bass and hi uegills has the following points in its favor: ., ,. February. 1943 BENNETT: MANAGEMENT OF ARTIFICIAL LAKES 371 1. Both species are well suited to the artificial lake habitat and are much sought by anglers. The largemouth bass is Illi­ nois' most important large game fish, and the bluegill is a favorite pan fish with fly fishermen. 2. The bluegill is very prolific and spawns throughout the summer. Enough young are produced to maintain an ade- hoopnets were fished for 1 week each month from March to November, in­ clusive, during 1939, 1940, 1941 and part of 1942, and all fish caught were removed from the lake. Hook-and-line fishing was more effective than hoopnets in removing largemouth bass. The total yields for these years are shown in table 4. As the lake was cropped, no attempt was Table 4.-Fish yields from Fork Lake, near Mount Zion, Ill., 1939, 1940, 1941 and 1942.• BLUEGILLS LARGEMOUTH BASS YEAR Total Average Total Average Number Weight, Weight, Number Weight, Weight, Pounds Pounds Pounds Pounds 1939 ................. 940 172 .4 0 . 183 349 51.0 0 .146 1940 ................. 778 146 .2 0 .188 217 52 .9 0 .224 1941 ................. 503 71.8 0 .145 185 57 .3 0 .309 1942* ................ 253 37 .5 0 . 148 40 22 .7 0 .568 - - -- - - - Total .............. 2, 474 427 .9 791 183 .9 Combined yield-3,265 fish, weighing 611.8 pounds. • Cropped from March through June , 1942. quate population for angling, as well as to furnish forage for bass. 3. There is little food competition be­ tween these two species. Bass feed upon young bluegills, crayfish, adult aquatic and terrestrial insects and the nymphs of drag­ onflies and damselflies; bluegills on ento­ mostraca, midge larvae and aquatic vegeta­ tion ( particularly algae). 4. The.use of these fish allows lakes to remain clear, thereby increasing their rec­ reational and aesthetic value. A yield study of the bass-bluegill com­ bination was made at Fork Lake, near Mount Zion, Ill. The area of this pond during the past 4 years has varied between 1.00 and 1.38 acres ; the maximum depth from 7 to 9 feet, depending on the water level. Two publications give in detail the results of investigations in 1938 and 1939 (Thompson & Bennett 1939; Bennett, Thompson & Parr 1940) . In 1938 the lake was poisoned because it contained many undesirable fish, and restocked with 270 stunted adult bluegills and 1,440 largemouth bass fry. No more fish have been placed in the lake since this restock­ ing in 1938. Intensive cropping was begun in 1939, use being made of both hoopnets and hook-and-line fishing. Six 1-inch-mesh made to protect either bass or bluegills during the spawning season, and the lower size limit of the fish taken was controlled ordinarily by the mesh of the nets used. On some net raises, however, very small fish were trapped when the meshes be­ came bunched. A small number of blue­ gills less than 2 inches long were caught in this manner. In 1941, the yield of blue­ gills was smaller than in previous years, although the bass yield was somewhat larger. This small yield of bluegills in 1941 was due in part to the poor survival of bluegill fry until late summer in 1939. During most of the bluegill spawning sea­ son in 1939, young bass 5 to 7 inches long fed upon bluegill fry before they left the nests. A field observation on this point was verified by stomach analyses of many bass. Further analyses of the fish yields for these years show that 39.2 per cent of the bluegills taken in 1939 were of desirable size or larger ( 6 or more inches) ; 60.6 per cent in 1940 and 38.4 per cent in 1941. Legal bass ( 10 inches or larger) made up 0.85 per cent of the catch in 1939; 8.8 per cent in 1940 and 29.5 per cent in 1941. The largest bluegill taken weighed 0.74 pound, and half-pound bluegills were fair- 372 lu.1:-.01s ~ATURAL H tsToRY S u R,'EY B uLLET IX Vo l. 22, .1rt. 3 h- numerous. The growth of bass was ;hout anrage for most l lli nois waters, fig. 5. The hook-and-line catch in F ork Lake was 2.8-1- fo,h per man-hour in 1939 ; 3.23 fish per man-hour in 19-1-0 and 2. 98 in 19-t-l. Thi-. catch was made up almost ex­ clusi\'eh· of hass, as art ificia l baits having hooks too large for bluegi lls w e re com­ monly used. T he figures on ca tch per man­ hour are hased on both illegal and legal hass, as all were kept. The maximum catch was made in Ap ril , 19-1-0 , when 27 small hass were taken in 2 man-hours of fishing. P re\"ious to the remornl of rough fish and hullheacl s in 1938. Fork Lake ,vas \"err muddy and devoid of aquatic vege­ tation. \ \'hen th ese fish were remoYed and replaced by bass and bluegills, the water cleared and rema ined clear, and after a few weeks the wate r weed , Potnmogetou f o/irm15 Rafi nesque, appeared. This weed spread duri ng 1939, 19-1-0 and 19-1-1, until it formed dense mats in all shallow water up to 5 fee t in depth. These dense tangles of coarse vegetation offered excellent pro­ tection for young bluegills, but nry little food. During the summer of 19-1-1 when th is vegetation was most abundant, small bluegills and bass of all sizes grew slowly because large numbers of young bluegills swarmed in the plant mats, but found little nourishment , and the hass were unahle to use them for food. Howe\'Cr, in August the weed practically disappeared within a few weeks and almost concurrentlr the bass bec:une verr fat, prohahly th~ough assimilation of the o,·erahundant small bluegills. Higher aquatic plants arc a detriment to small artificial lakes in that they pro­ mote the survival of too many young fish, fig. 6, and during their growing season they take up nutrient materials and light that would otherwise produce algae, the basic food of the aquatic environment. On July 8, 19-1-2, the Fork Lake experi­ ment was suddenly terminated hy abnor­ mal precipitation. On this date, a rain of approximately -+ inches caused the dam to hreak near the center, and a part of the 1:i~. 5.-Largemouth bass and bluegill!> from Fork Lake, near Mount Zion, III. , April, 19-H , showing 1938 brood bass and 1938, 1939 and 19-rn brood bluegills. Fdn·uary, 19-13 BENNETT : i\lANAGE\IENT OF ARTIFICIAL LAKES 373 fish population was washed across a corn­ field and into a small creek below. B,· chance Mr. Gernon P. Hesselschwerlt and the author arrived at the lake when about two-thirds of the water had passed out of the basin. The larger fish remain­ ing in the lake at that time were captured pounds. These hass had hecome so "edu­ cated" that fe"· of them would enter hoop­ nets or bite on artificial haits. About 30 large bluegills, belonging to the 1938 brood ( + years old; weight be­ tween 0.50 and 0. 7 5 pound each) " ·ere taken, but most of the bluegills caught in Fig. 6.-Aquatic vegetation planted by the U. S. Soil Conservation Service around a farm pond in Adams County, Ill. This type of vegetation, while useful in controlling soil erosion, promotes the survival of too many young fish and often becomes so dense that bank fishing is nearly impossible. by placing a section of hoopnet lead across the break. As it was impossible to estimate the numbers of bass and bluegills that had been washed out of the lake, particular attention was directed to the remnants of the original stock of fish. Thirty-four of the original bass, averaging 1. 7 6 pounds each, were caught in the net and 32 "·ere left stranded in the lake basin. Apparently the initial rush of water through the broken levee was considerable, as corn stalks were flattened over a wide area in the field below the lake. Any fish near the point of break must have been washed out shortly after the dam gave way. It there­ fore does not seem unreasonable to assume that nearly 100 of the original bass may have been present. The bass population, including the original stock, 19+0, 19+ 1 and 19+2 broods, probably numbered sev­ eral thousand. The total weight of those observed was estimated at about 200 the net were 1939 and 19+0 brood fish and averaged 6 inches long. Thousands of young hluegills of the 19-+2 brood were left stranded in heds of Pota111ogeto11 foli­ osus. None of the original bluegills were taken. Fish technicians and sportsmen have long been interested in returns from fish stocked in various waters, but little con­ crete information is available, except from trout stream investigations. The recognition of the original stock of hass and bluegills recaptured from Fork Lake was possible because scale samples were taken from all fish. lVIoreover, as the adult bluegills were 2 or more years old when placed in the lake, they were easily separated from the younger fish. Large­ mouth bass were stocked as frr in 1938, and no you ng were spawned t~ntil 19+0. Thus no difficultr was encountered in distinguishing the~ from the 19+0 and 3H l1.1.1~01s :--. .,TURAL H1 sTORY .. UR \ ' EY B uu.ETI~ f'ol. 22. Art. 3 19-t- I brood~ of bass. Table 5 gives the numbers of these lish recaptured in four fishing seasons since the bass and hh1egills \\'ere placl'd in Fork Lake. These returns must be considered nearly " optimum" because the lake contained no other fish when the bass an d bluegills were introduced, and food competition was kept at a minimum b,· constan t cropping. The original bluegill~ could ha\'e suffered no predation from the hass as they were al- poor in crayfish , the ba::-s-bluegill combina­ tion might be improYed by introducing crustaceans of species locally abundant. 5. Bass and bluegills will maintain their numbers under intensin fishing. It i-. estimated that Fork Lake was cropped to the extent of about one-half of its car­ rying capacity for these species during the -t- years covered by the study. 6. In some lakes where the fishing pressure is light, it may he necessary to Table 5.-Heturns from the original planting of 2i0 adult bluegills and 1,440 largemouth bass fry in Fork Luke, June, 1938. B LUEGILLS L ARGEMOUTH BA SS YEAR Per Cent of Per Cent of ::--.'umber Original ::--.'umber Original Stock Stock 1939 ............. .. ... . ... 162 60 .0 349 24.2 1940 . ............. . ....... 27 10 .0 217 15. 1 1941 . ................. . ... 2 0.7 74 5 .1 1942 .. .................... 0 0.0 66* 4.6* - -- - -- Total ................. 191 70 . i 706 49 .0 • Collections from :\larch through .June plus fish sal\·agetl from \\·ashout. ways too large to be taken. · Smaller re­ turns from the hass are undoubtedly the result of cannibalism during 1938 and 1939. Fourteen other lakes have been stocked with hass and hluegills and followed as carefulh· as time would allow. The infor­ mation ·from Fork Lake , and other lakes containing bass and bluegills, suggests the following points of interest in regard to the use uf this combi nation: I. There is a marked improvement in fishing, especially for bass, over that fur­ nished by mixe