Biological Survey — Oswego Watershed 65 



torn of the thermocline in most of the lakes and, in general, marks 

 the division between warm and cool water during the summer when 

 the feeding and general life activities are at the maximum. We 

 believe that bass and pickerel confine their attention mostly to 

 water shallower than 50 feet but the perch, which is the commonest 

 and most generally distributed shallow water fish in the lakes, was 

 taken in considerable numbers at depths from 40 to 55 feet. The 

 150 lake trout captured by our fishermen were taken at an average 

 depth of 85 feet. 



In all the lakes excepting Otisco the supply of oxygen and the 

 scarcity of carbon dioxide is such that they are fit for fish habita- 

 tion to their remotest depths, so far as the gaseous content of the 

 water is concerned. 



In Canandaigua, Owasco and Skaneateles the absence of the 

 common scud (Gammarus) is associated with a comparative scarcity 

 of large yellow perch. 



The presence of plankton Crustacea in the Finger lakes in 

 quantities assumed to be adequate* furnishes the most important 

 clue for an improvement of the fish supply. These minute Crusta- 

 cea are utilized directly as food only by the young fry and finger- 

 ling of our important food fishes. But the plankton sifters like 

 the alewif e, whitefish at certain seasons and smelt utilize this boun- 

 tiful food supply and, in turn, are devoured by the lake trout, 

 whitefish, perch and bass. The greatest hope, therefore, for the 

 improvement of fishing in these three lakes lies in the introduction 

 of ale wives (sawbellies) or some equally good plankton feeders. 

 Alewives can be taken by the thousand in Seneca lake and imme- 

 diately transported in trucks to the other lakes. The objection to 

 the alewife that it sometimes dies in great numbers, when it be- 

 comes unduly abundant, seems a question of minor importance. 

 No complaints against this fish were heard on Keuka lake where 

 it has been common for fifty years. On Seneca lake there have 

 been complaints early in the summer of the odor of decaying ale- 

 wives about once in five to seven years. But some of the more 

 intelligent cottagers have maintained that this apparent nuisance 

 is really a blessing because when they gathered the dead alewives 

 from the beaches and buried them in the garden, they found them 

 to be a very valuable fertilizer even as our Puritan forefathers 

 found them at Plymouth. During the summer of 1927 there was 

 no mortality noticeable in the alewife population. 



In connection with the general problem of utilizing the plankton 

 in these lakes, it must be borne in mind that these immense vol- 

 umes of water, amounting to many billions and even trillions of 

 cubic meters in some of the lakes, support a vast amount of 

 plankton Crustacea f which can be turned into nourishment for our 

 larger food fishes only through the agency of such plankton sifters 

 as the alewife, smelt and cisco. 



* See Birge and Juclay (loc. cit. ) . 



t See Charts 1-8, p. 144; chart 9, p. 154. 



