. Bulletin. Natural history; Natural history. 'February, 1943 Bennett: Management of Artificial Lakes 369 inderfished, the total poundage of fish re- nains at or near the maximum carrying :apacity of the lake. The fish are living )n a subsistence basis and grow very slow- y, if they grow at all. Frequently fish middle of the third summer, the remain- ing fish were censused by poisoning the lake. A comparison of this census with the theoretical pyramid of numbers indi- cates that overfishing removes the top from. Fig. 4.âOnized Lake on the recreation grounds of the Owens-Illinois Glass Company
. Bulletin. Natural history; Natural history. 'February, 1943 Bennett: Management of Artificial Lakes 369 inderfished, the total poundage of fish re- nains at or near the maximum carrying :apacity of the lake. The fish are living )n a subsistence basis and grow very slow- y, if they grow at all. Frequently fish middle of the third summer, the remain- ing fish were censused by poisoning the lake. A comparison of this census with the theoretical pyramid of numbers indi- cates that overfishing removes the top from. Fig. 4.âOnized Lake on the recreation grounds of the Owens-Illinois Glass Company near \lton, 111. This lake, which produced a hook-and-line yield of nearly 350 pounds of fish per icre in 1939, represents the only overfished lake ever observed by the Illinois Natural History iurvev. hat are long enough to interest anglers ire so emaciated that they are not kept vhen caught. Commonly, fish in these rrowded lakes are about the same size as ish one-half their age in properly cropped vaters. Although we have records of a number )f lakes that have produced high fish â ields, in only one instance do we have a :omplete story of overfishing. In this case, Dnized Lake, fig. 4, the body of water *vas relatively small and the fishing in- ensity very heavy. During the 1939 fish- ng season the hook-and-line yield was al- nost 350 pounds per acre. The yield ;tudy covered a period of two seasons and 3art of a third. The yield was very high luring the first season, but lower and ower during the next two seasons. In the the pyramid, fig. 3. The census included a large number of fish, nearly all belong- ing to the three youngest age groups. Overfishing decreased the catch per man- hour as well as the average size of the fish caught, until few fish of desirable size were taken. The effect of overfishing on the growth rate of the population remaining at the time of poisoning is being deter- mined by scale studies. Apparently the young fish that had escaped the anglers were gr
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