114 Reproduction, Competition, and Predation 



ing of a water area that already contains fish is largely useless; it is 

 better to kill all the fish and start again with correct numbers of selected 

 fish. 



(3) Poor results may be obtained because the fish stocked in new or 

 renovated ponds died after they were released "in good condition." Even 

 though the fish released were active and swam into deep water in a 

 normal manner, they may have sustained injuries through handling prior 

 to release that later resulted in their death. 



For example, Brown ^^ found the survival rate of bass fingerlings in 

 bass-bluegill stocking experiments ranged from 47.1 to 83.3 per cent. 

 Other investigators have obtained 69.2 to 100 per cent survival "^^ and a 

 75 per cent survival for one pond.^*" 



A striking example of this type of injury was observed by the author 

 while tracing the final dispensation of the original adult and yearling bass 

 released in Ridge Lake (Illinois) in 1941.^^ These bass consisted of 58 

 adults from Crab Orchard Lake near Carbondale, 42 adults from Lake 

 Chautauqua near Havana, and 335 yearlings from Lake Glendale near 

 Robbs. 



The 58 Crab-Orchard-Lake bass were caught and held in wing nets, 

 April 27-29 inclusive, moved into a tank truck supplied with an air 

 compressor, and transported to Ridge Lake, a distance of 150 miles by 

 road. The weather was unseasonably warm for April. Although the fish 

 appeared in good condition when released, 44 of these fish (75.8 per cent) 

 were believed to have died, soon after release, from injuries sustained in 

 capture and transportation. These 44 bass were not caught by anglers in 

 1941 and 1942 and were not present when the lake was drained in 1943. 



The 42 adult bass from Chautauqua Lake (also caught in wing nets) 

 were the survivors of a much larger number taken in March and April 

 and held indoors for several weeks in aerated holding tanks. Fish injured 

 in netting operations were removed and discarded. On May 1, bass re- 

 maining in the tanks were transported in the early morning to Ridge Lake, 

 a distance of 145 miles. Sixteen of the 42 bass disappeared without a trace 

 and probably died from injuries (38.1 per cent). 



The 335 Lake Glendale yearlings (5.0 to 7.0 inches) were seined on 

 June 17, held overnight in a holding net staked out in the lake, and then 

 were hauled in aerated tanks to Ridge Lake— a road distance of 180 miles. 

 The weather was hot, and a few of the fish died in transit, but those 

 released appeared to be in good shape. In this group, 317 of the 335 bass 

 (94.6 per cent) disappeared. Some may have been eaten by the larger 

 bass, but with only 100 of the larger bass released in 18 acres of water, 

 the fish were not crowded and predation probably was not heavy. The as- 

 sumption that these fish died from improper handling was further sub- 

 stantiated by the high survival rates of marked bass which were recorded 



