190 Fishing and Natural Mortality 



exceeded 1400 man-hours per acre; the catch amounted to 350 pounds 

 per acre for the first year and then dropped to 142 pounds per acre the 

 second. This drop in yield suggested overfishing. When the pond was 

 completely censused in June of the third year (after a spring catch of 

 71 pounds per acre had been taken by a fishing pressure of 634 man-hours 

 per acre ) , it contained 9171 fish ( exclusive of the young of the year which 

 were largely lost or eaten by larger fish), but only 481 of the larger fishes 

 were of desirable * sizes. The lake contained largemouth bass, black 

 crappies, bluegills, green sunfish, yellow bass, black and yellow bull- 

 heads, golden shiners, and a few fishes of several other kinds. Of the 

 important fishes in the hook-and-line catch for the preceding two years, 

 the black crappies had been reduced to 22 fish, the yellow bass to 4, and 

 the black bullheads to 2 fish. There were 275 bass, of which 12 fish ranged 

 from 3 to 6 pounds each. At the time of the census there were 23 bass of 

 at least 10 inches in length per acre. Bluegills were represented by 6545 

 fish, warmouths by 1638, green sunfish by 245, yellow bullheads by 347, 

 and golden shiners by 90. Fishes grew at moderately slow rates until they 

 reached desirable sizes and then, very rapidly because of population 

 thinning through angling. If fishing had been continued at this rate for 

 another season, the populations of black crappies, yellow bass, and black 

 bullheads might have disappeared entirely. However, the census gave 

 evidence that largemouth bass, bluegills, warmouths, green sunfish, yellow 

 bullheads, and golden shiners might be able to maintain populations in- 

 definitely, either because of high reproductive success with high survival 

 of young or because of increased resistance to capture, or for both of 

 these reasons. One season with reduced fishing pressure would have al- 

 lowed the population to expand to approach the carrying capacity of the 

 pond and obscure all evidence of overfishing. 



Fishing Pressure versus Yield 



In 1950 and 1951, Barnickol and Campbell ^ studied the fish yields of 

 many small impoundments located on the August A. Busch Memorial 

 Wildlife Area near St. Louis, Missouri. These ponds were fished at rates 

 ranging from about 300 to 4000 man-hours per acre per season, and yields 

 varied from as low as 20 to as high as about 300 pounds of fish per acre. 

 In 1959, Gilbert F. Weiss, Fishery Biologist for Missouri, furnished addi- 

 tional data on fishing pressures and yields from the Busch ponds as well 

 as from several other Missouri lakes that were fished less heavily. 



The 26 impoundments of one to 20 acres on the Busch Memorial Wild- 

 life Area were not all in use during all years between 1949 and 1959, but 



* Desirable sizes were arbitrarily set as follows: at least 10 inches for largemouth 

 bass (legal limit); 8 inches for crappies; 7 inches for yellow bass, bullheads, and 

 golden shiners; and 6 inches for bluegills, warmouths, and green sunfish. 



