Predation 115 



in later years when the lake was drained in March, the fish censused, and 

 the marked fish returned immediately to the refilling lake basin. One of 

 the Chautauqua Lake fish that survived the original road trip and stock- 

 ing in 1941 later survived 4 lake drainings and fish censuses and was 

 caught by a fisherman in 1949. 



Stroud "^^ tagged fish released in Massachusetts ponds in order to 

 measure the recovery from angling of largemouth and smallmouth bass, 

 pickerel, bullheads, white perch, and yellow perch. He recorded several 

 instances of high mortality shortly after stocking, presumably from injury 

 during handling prior to release. 



Fingerlings or fry may be more or less sensitive to rough handling and 

 poor water conditions during transportation and stocking than yearling 

 or adult fish. However, stocking ratios of bass and other fish mean little 

 if the stocking mortahty is abnormally high. A 10 per cent loss of bass or 

 bluegills in a specific stocking ratio might mean little, but a 75 per cent 

 loss of the bass (or bluegills) through unsuspected injury during trans- 

 portation and stocking would certainly influence the future dynamics of 

 a bass-bluegill population. 



Most hatchery men and biologists recognize the need for extreme care 

 in the handling of fish to be stocked. The problem is largely related to 

 the shortness of the season for moving fish (late fall and to a lesser 

 extent early spring ) and the magnitude of the operation. Often, inexperi- 

 enced help must be used in the handling and moving of fish which con- 

 sequently become overheated or exposed to other unfavorable conditions 

 before their final release in new locations. 



Some hatchery ponds are too badly silted for fish to be removed without 

 having to hold them in silt-filled water for comparatively long periods. 

 The danger here lies in the high-oxygen demand and the products of 

 anaerobic decay in this silt. Thus, unless an outside source of clear water 

 is directed into the pond to reach the fish concentrated in the seines, high 

 mortality is almost certain to follow. 



PREDATION 



The Role of Predation in Fish Management 



At the beginning of this chapter we noted that the fishes have inhabited 

 the earth for more than 350 million years and during this period have 

 been relatively successful. Part of their success was due to die develop- 

 ment of a high reproductive potential tliat allowed them to out-strip the 

 predators that evolved to feed upon them. As each higher class of verte- 

 brates appeared, certain members became predators of fishes, so that in 

 a modern fresh-water environment, fish predators are represented by a 

 variety of vertebrates each modified for predation activity in or on the 



