Fishing Mortality 195 



weather conditions because fishermen know that rising waters, for ex- 

 ample, stimulate certain species of fish to move about and feed. Most 

 sight-feeding fishes become inactivated by rising waters because increased 

 turbidity limits their vision. 



Returns from angling effort directed toward species of warm-water 

 fishes other than largemouth bass indicate that intensive fishing pressure 

 also depresses the rate of catch but not so rapidly as with the largemouth. 

 Thus it is safe to state that a leisurely pattern of angling over a season 

 is more conducive to satisfactory fishing than is an alternation of relatively 

 intensive angling with periods of complete rest. 



Factors Related to Rate of Catch 



The exact relationship between the number of fish per acre or per 

 acre-foot of water and the rate of catch is usually obscured by one or 

 more factors, some of which have been discussed previously. Quite obvi- 

 ously there must be some relationship between numbers of fish available 

 and catch rate, but often the relationship is clear only when numbers of 

 fish are reduced to a very low figure.^- 



Stroud ^^ studied the recovery of marked "salvaged" fishes released in 

 Massachusetts lakes and ponds to gain information on the relationship 

 between available fishes and angling returns. He could only estimate 

 roughly the population density of the various marked species recovered. 

 Thus, he calculated an over-all harvest of 9 per cent ( from 10 ponds ) for 

 marked largemouth bass, with a somewhat higher return for smallmouth 

 bass; whereas marked chain pickerel ranged from 15 per cent to 59 per 

 cent. Recaptures of other warm-water pond fishes were usually between 

 those for bass and pickerel, although in some instances a large per cent 

 of the salvaged fishes did not survive. 



The presence of more pan fishes, such as bluegills, crappies, yellow 

 perch or bullheads, per unit of water, could conceivably mean better 

 fishing. One reason for poor fishing in unfertilized Alabama ponds given 

 by Swingle and Smith ^^ is that the "water is too poor to support many 

 legal-sized fish." However, Hansen et alr^ were unable to show that the 

 rate of catch in fertilized ponds (which contained somewhat higher 

 poundages of fish than the control ponds) was consistently better than 

 in the control ponds. 



Lux and Smith ^^ attempted to discover which of a number of physical, 

 chemical, and biological factors bore a relationship to seasonal changes in 

 the angler's catch in a Minnesota lake. They concluded that as the avail- 

 able food supply increased after the middle of June, the fishing became 

 progressively poorer. This may explain a seasonal cycle, but cannot be 

 used to explain trends extending over several seasons. 



Evidence shows that rate of growth of fishes and rate of biting are often 



