Stocking 113 



reservoirs was an example of this type of stocking.^- McCaig, Miillan, and 

 Dodge ^'^ recorded that the introduction of smelt into Quabbin Reservoir 

 ( Massachusetts ) furnished an improved food supply for lake trout so that 

 the latter reached a length of 18 inches in their fourth year instead of the 

 fifth as they had done before the smelt were abundant. 



This type of stocking should be considered very carefully before it is 

 done because: (1) food chains of fishes are very complex and the intro- 

 duced species may not serve the purpose intended; moreover, (2) forage 

 fishes that are capable of expanding their populations in the face of 

 existing populations of predatory species already present may constitute a 

 danger from overpopulation as the gizzard shad has done in some waters. 



Invertebrates such as crayfish, scuds, and insect larvae are sometimes 

 stocked in new ponds and small lakes, and these stocking attempts are 

 frequently successful. 



Failures in Stocking Fish 



Biologists in various parts of the country have developed stocking 

 numbers and ratios of fishes intended to give satisfactory results in fish- 

 ing returns. However, these stocking recommendations sometimes result 

 in poor fishing or no fishing. There may be one or several reasons for 

 these unsatisfactory results: 



(1) Poor fishing in new impoundments may result from unauthorized 

 stocking prior to or after the lake or pond has been stocked with tested 

 ratios of kinds and numbers of desirable fish. Krumholz ^^ mentions the 

 problem of maintaining uncontaminated hybrid ponds in southern In- 

 diana. In Illinois, and probably in most states, there are fishermen who 

 spend a part of their time as amateur fish managers; one of their main 

 activities is the promiscuous stocking of small numbers of most of the 

 kinds of warm-water fishes to be caught on hook-and-line. If one finds 

 bluegills where red-ears were stocked or largemouth bass where there 

 should be smallmouth bass only, one may be observing the work of an 

 amateur fish manager. Many fishermen release left-over live minnows 

 into streams or lakes; the contamination from the minnows may be of 

 minor importance if none of them are goldfish, carp fingerlings, or suckers. 



(2) Some contamination takes place, usually in lakes or ponds near 

 large urban centers of population, through the release of aquarium fishes 

 when the owners tire of caring for them. Goldfish usually survive but 

 guppies and other tropical fishes cannot winter over except in the deep 

 south. 



New waters that have been contaminated with local warm-water fishes 

 soon become useless for fishing unless through accident a reasonable 

 number of bass are also present. As discussed previously, corrective stock- 



