Biological Survey — Erie-Niagara Watershed 



221 



shore line to the middle of the channel. The findings shown in 

 Table 1 are based upon streams above and below 18 feet in width. 

 The dividing point at eighteen feet was selected because this 

 seemed to be the width of stream found in this vicinity where 

 bottom foods are quite evenly distributed over the entire floor of 

 the stream. 



Table 1. — Distribution of Available Fish Food in Streams Above and Below 



18 Feet in Width 



The average weight of nutritive elements per sq. ft. found at 

 the sides of streams was 0.92 grams (Table 1) in streams above 

 18 feet in width. The average for centers of streams of the same 

 width was 0.81 grams, a decrease of 11.95 per cent or approxi- 

 mately, one-eighth. On the other hand, in streams below 18 feet 

 the average weight of the nutritive elements at the sides was 1.44 

 grams; centers, 1.64 grams, giving an increase of 12.19 per cent 

 or approximately one-eighth, from shore line to mid-channel. Thus 

 it is seen that in streams below 18 feet in width more food is found 

 in their centers, and they are proportionately much richer at 

 both sides and centers than streams above eighteen feet in width. 

 Also these figures show that there is a slight decrease in the amount 

 of food present in the middle of streams over 18 feet in width, as 

 contrasted with the amount contained at the sides of streams of 

 this width but this decrease is so slight that we may consider it to 

 be negligible. 



This is not in agreement with the findings of Leger. However, 

 the figures given here are the averages derived from 91 unit area 

 bottom studies taken in many types of trout streams under varying 

 conditions as they are found in the vicinity of Ithaca, N. Y., and 

 while these results may be true for streams in this vicinity, very 

 dissimilar conditions might be found in the streams of France in 

 which Leger w^orked. 



Multiplicity of Factors. — Table 1,* p. 195 of last year's report 

 on this problem shows that the individual unit area bottom studies 

 varied tremendously in the weights of available fish food present. 



Loc. cit. 



