Biological Survey — Genesee Rrt^r 25 



1. Streams showing poorest conditions — pools generally shal- 

 low without shelter. 



2. Streams showing average conditions in which deep sheltered 

 pools are fairly numerous. 



3. Streams showing best conditions in which the pools are large, 

 frequent and well sheltered. 



Enemies, Effects of Angling. — Water snakes, green herons 

 and kingfishers are responsible for some of the losses in streams, 

 although we have no means of estimating how large they are. 

 One may be reasonably sure, however, that man is the principal 

 agency in removing the legal size trout. 



The few good trout streams of the Genesee watershed are all 

 heavily fished, and if w^e were to estimate that one-half of the legal 

 sized trout were removed each year, it would probably not be too 

 much. 



The relative losses of fingerlings and advanced fry is a matter 

 difficult to analyze. Hatchery experience tells us something about 

 it, but trout reared in a hatchery are subject to many diseases 

 which do not give trouble in wild waters. On the other hand, 

 hatchery trout are protected from the ordinary enemies that 

 operate in wild waters. To some extent one balances the other. 



In the calculations of the Genesee system, we have assumed that 

 95 per cent of the advanced fry and 50 per cent of the fingerlings 

 are lost before the legal size is reached. The number of survivors 

 in the two cases would be in the proportion of one advanced fry 

 to ten fingerlings. 



Productivity of a Unit Area. — A series of experiments was 

 undertaken in the Experimental Hatching Station of Cornell 

 University for the purpose of obtaining some definite information 

 in regard to the productiveness of a unit area of running water 

 under varying conditions of food supply. The lowest average 

 production under the condition of food scarcit}^ was equivalent 

 to about 75 pounds of trout per acre ; the highest obtained in races 

 in which food animals were very abundant approximated 300 

 pounds. These have been taken as the extreme and an interme- 

 diate value of 187 pounds has been assumed to approximate aver- 

 age conditions. 



A trout of 8 inches is not far from the average size occur- 

 ring in the streams of this section of New York, and according 

 to a series of weight-length measurements a w41d trout of 8 

 iiiches will average about one-fourth of a pound. An acre of 

 stream should therefore support about 1,200 8-inch trout if 

 rich in food, 750 if average conditions obtain and 300 when poor 

 in food. 



We have already estimated that about one-half of the trout are 

 caught by anglers and that about one-half of the fingerlings 

 planted disappear from one cause or another. Therefore, one 

 should plant double the number caught which is equal to the 

 total number supported by the stream. 



