Biological Survey — Oswego Watershed 55 



summer so that a very small proportion of the fry of fish which 

 run up the streams to spawn ever reach the lake successfully. 



(6) Obstructions in the outlets have also had an effect. An illus- 

 tration in the case is mentioned under the distribution of the eel. 

 When fish that were bred in the shallow lagoons of the Seneca 

 river could run up into Cayuga lake and into other lakes of the 

 chain from their outlets, there was a fresh invasion each spring 

 or summer from the streams which tended to maintain a vigorous 

 stock and restore the fish population of the lakes from the more 

 favorable breeding grounds downstream. These obstructions in 

 the outlets of all the lakes are now practically prohibiting migra- 

 tion of fish such as was possible 50 or 100 years ago. 



(7) Destructive enemies of the fish we believe are accountable 

 for a large part of the scarcity of lake trout in Canandaigua, 

 Cayuga and undoubtedly in the other lakes. But in Canandaigua 

 the burbot, which is found in the deep water, is a voracious fish 

 and feeds on any kind of fish it can capture. It is unquestionably 

 a scourge of the spawning grounds, devouring the fry and eggs of 

 the trout and so preventing to a large extent the natural repro- 

 duction of this fish. He is, of course, an equal enemy of the white- 

 fish and the cisco. 



In Seneca and Cayuga lakes the lamprey is a deadly enemy of 

 the trout and all soft scaled fishes. It even attacks carp and bow- 

 fin successfully. However the belief that whenever a lamprey 

 attacks a trout the trout is doomed, must be abandoned, for a large 

 proportion of the trout which we took during the survey bore from 

 one to seven lamprey scars which had healed over completely and 

 the trout was in vigorous condition. The lamprey, of course, sucks 

 the blood of the trout until he is satisfied and then drops from the 

 fish and the wound heals if the fish is sufficiently vigorous or if 

 the wound does not pierce the abdominal cavity. But in the case 

 of young trout, although we cannot prove it, we believe that the 

 attacks of the lamprey are generally fatal. We took no young 

 trout under 18 inches in length which showed a lamprey scar. A 

 further study of this situation is advisable. 



Besides the burbot and lamprey many fishes are destructive to 

 the young or the eggs of trout and other food fish. Perch have 

 been taken repeatedly near the spawning grounds of trout with 

 the stomach fully distended with trout eggs. Bullheads have the 

 same habit and, although they probably do not invade the trout 

 grounds to any extent, are destructive of the fishes which breed 

 in the shallows. The sculpin and the spot-tailed minnow are fre- 

 quently called "spawn eaters." Unfortunately most of our fishes 

 often destroy the spawn not only of other fishes but their own, 

 as has been conclusively proved of brook trout and other fish kept 

 in hatcheries. 



The softshell turtle (Amy da spinifer) which inhabits Keuka, 

 Seneca and Cayuga is a predacious species which frequently feeds 

 on fish. The same is true of the generally distributed snapping 



