Fishing Mortality 193 



maintain a catch rate of 0.50 pound per hour they would need to con- 

 struct a lake of about 107 acres: 



(1) Figure 7.2: For an average catch rate of 0.50 pound per lioiu- the 

 fishing pressure should be about 75 man-liours per acre per season. 



(2) 8000 ^ 75 = 106.6 acres. A lake of this size might cost $1000 to 

 $1500 per acre or $110,000 to $160,000. 



Types of Fishing Pressure 



The total hours of fishing and the fishing schedule vary greatly from 

 lake to lake. For example, a lake open to the public may be fished at a 

 high rate during May and June and then chiefly on weekends during 

 July, August, and early September. Where both boat and bank fishing 

 are permitted, the daily pressure may be very high— as much as 50 man- 

 hours per acre per day if the fishing is good. But at this level of fishing, 

 the rate of catch will drop off very markedly in 4 days or less. 



At Ridge Lake (Illinois) where bank fishing was not permitted and 

 only 7 boats were a\ ailable on 18 acres of water, the approximate rate of 

 accumulation of fishing hours was 9 or 10 per acre per day. As the lake 

 was open 5 days per week, we can estimate a fishing pressure of about 25 

 to 50 man-hours per week during the first week; later in the season the 

 pressure was less.^ 



Many private lakes and farm ponds are fished in a leisurely manner: 

 On one day three fishermen fish for a total of 12 hours, but the pond is 

 not visited by fishermen again for several days or weeks. The accumulation 

 of fishing hours is so slow that only 50 hours per acre are logged for an 

 entire season. The same may be true for large reservoirs but for a dif- 

 ferent reason: some artificial reservoirs are so large that the fishing 

 pressure of all available fishermen builds up a seasonal pressure of only 

 a few dozen hours per acre. 



As fishes react in different ways to various levels of fishing, the schedule 

 and intensity of fishing affects the yield. The bass in Ridge Lake showed a 

 much reduced catch rate after the morning fishing period of the opening 

 day (Figure 7.3), and by the end of the third day, the rate had nearly 

 reached a low point for the summer— after only about 25 hours of fishing 

 pressure per acre.^ Creel censuses on three Kentucky lakes demonstrated 

 that 70 per cent of all largemouth bass caught during the first week were 

 taken in the first 30 hours of fishing. ^-^ 



Records of the largemouth bass catches from relatively infertile un- 

 managed waters in Virginia indicated that about 19 trips per acre re- 

 moved the "harvestable surplus" of these fish amounting to 3.6 bass per 

 acre averaging approximately a pound each."^^ According to Martin ^^ 

 there is an easily harvested segment of any bass population which can 

 be readily taken at a high rate of catch by light fishing pressure. After 



