Fishing Mortality 191 



sufficient records were available to furnish data on more than 100 pond- 

 seasons.* Some stocking of ponds was done during the period but the 

 numbers of fishes released were usually insignificant in relation to the 

 fishing pressures and ^ ields and no measurable effect of stocking could 

 be demonstrated in the rate of catch. 



Data on rates of catch for various fishing pressures on the Busch ponds 

 and se\'eral other Missouri impoundments were combined witli similar 

 information from some lakes and ponds in central and southern Il- 

 linois.^' -^ All of the ponds contained largemouth bass and bluegills and 

 sometimes, in addition, red-ear sunfish, green sunfish, bullheads, and 

 channel catfish. These pond-season records were plotted in Figure 7.2 ^- 

 as symbols and a line drawn by inspection, representing the average 

 relationship between man-hours of fishing per acre and rate of catch in 

 pounds of fish per man-hour. 



Figure 7.2 shows that the seasonal rates of catch from 4000 man-hours 

 per acre to about 300 man-hours per acre were averaging about 0.10 

 pound per hour of fishing, and that within this range of pressures there 

 was no change with increasing man-hours per acre. Very few fishermen 

 will continue to fish if their catch rate does not exceed 0.10 pound per 

 hour unless a fishing trip is combined with picnicking or escape from an 

 unfavorable environment, such as might be produced by the heat and 

 noise of a big city. 



With decreasing fishing pressures from 300 down to 130 man-hours per 

 acre the rate of catch increased gradually and at a rather slow rate, i.e., 

 from 0.10 to 0.23 or 0.21 pound per man-hour. Below a seasonal pressure 

 of 130 man-hours per acre the rate of catch increased very rapidly until 

 in the best ponds at fishing pressures of 40 to 60 man-hours per acre the 

 rate of catch averaged 1.0 to 1.5 pounds per hour. These very high rates 

 of catch were attained only where populations contained a high per- 

 centage of fish of useful sizes. 



If it is assumed that the curve in Figure 7.2 represents a reasonably 

 accurate relationship between a building-up of fishing pressure and a 

 depreciating rate of catch for largemouth bass and bluegills (or other 

 sunfish), the curve can be used to estimate the hours of productive fish- 

 ing that a lake of a given surface area may furnish each season. Also, an 

 owner of a private lake might employ it in maintaining the proper level 

 of fishing pressure for a high catch rate. In reverse, it could be used to 

 figure the size of artificial impoundment needed to satisfy the fishing 

 pressure level of a fishing club of predetermined membership. 



For example, if the estimated total annual fishing pressure for the 

 members of a club approximated 8000 man-hours and they wished to 



* A pond-season is one pond fished for one season. 



