Biological Survey — Erie-Niagara Watershed 



223 



they are valuable in many other ways to trout than in merely food 

 production. 



Relation of Type of Bottom to Quantity of Food. — Table 3 

 gives a summary of the stream bottom types studied during the 

 past two summers with the relative amounts of food found in each. 

 While this year's results differ slightly from those obtained in 1927, 

 the same proportionate amounts of food were found in each type 

 of bottom. As is shown in Table 2,* silt produced an average of 

 4.29 grams per one sq. ft. in 1927 while this year an average of 

 3.46 grams was obtained. Likewise there was a slight decrease in 

 the amounts found in rubble, coarse gravel and fine gravel, this 

 year. The figures presented here in Tables 2 and 3 show clearly 

 that there is a yearly fluctuation in the productivity of streams 

 in bottom foods. 



Table 3. — Stream Bottom Types Showing Average Amount of Available Fish 

 Food Per One Sq. Ft. in Each 



Foods Consumed by Trout by Comparison with Available 

 Foods. — Last season the relative abundance of each class of 

 available drift and bottom food was determined without cor- 

 relating these findings with foods actually consumed by trout. 

 This year trout were taken in connection with the drift and bottom 

 studies to determine, if possible, what foods of those available are 

 most largely consumed by trout. 



In order to determine the foods which trout selected from those 

 floating in or on the water, trout w^re seined or caught with 

 hook and line during the same time that drift food was being 

 collected from the water by the drift net. The net was run for an 

 hour for each catch and an attempt was made to obtain six trout 

 stomachs within the time that the net was in the water. The 

 later stomach examinations of the trout showed what foods of those 

 available the trout had selected. 



At the end of the summer a total of 29 drift catches and 147 

 trout stomachs were studied and tabulated in the laboratory and 

 the general results are presented in Table 4. Of the 147 stomachs, 

 32 were from rainbow trout, 6 from brown trout and 109 from 

 brook trout. The average length of all the fish w^as 6V2 inches and 



• See Oiwego Survty, p. 106, Table 2. 



