Biological Survey — Erie-Niagara Watershed 



227 



be noted that of all the foods consumed. 43.34 per cent were ter- 

 restrial and 56.66 per cent were aquatic in origin. Since these 

 trout were taken during June, July and August, when land 

 insects are most numerous, it is surprising to note that more than 

 half of their diet (56.66 per cent by number) is composed of 

 aquatics. The reverse is true of the available drift foods, wherein 

 89.87 per cent was terrestrial in origin, while only 10.13 per cent 

 was aquatic. 



As has been noted above with certain classes of foods, a greater 

 per cent has been consumed than was available in the drift. This 

 is significant because it indicates that trout must feed off the 

 bottom. It also may indicate, as seems to be tlie case with the 

 larger sized food organisms such as grasshoppers, moths, worms, 

 etc., that the trout were eating them before they had a chance to 

 reach the drift net. Furthermore, the larger terrestrial foods 

 would probably not drift far in a stream on account of their size 

 and structures. 



Aquatic Foods, Consumed and Available. — By referring to 

 Table 5 the principal preferred foods are shown. 



Table 5. — Comparison of Foods Taken in the Drift Net with Foods Consumed 



BY Trout 



Table 6.* — Comparison of Available Aquatic Fish Foods in Stream Bottoms 

 AND Aquatic Foods Consumed by Trout 



ORDER 



Available aquatic 

 foods 



Number Per cent 



Consumed aquatic 

 foods 



Number Per cent 



Mayfly nymphs 



Caddisfly larvae and pupae. 



Stonefly nymphs 



Fly larvae and pupae 



Beetle larvae 



Crayfish and shrimps 



Miscellaneous 



2,316 



1,335 



921 



476 

 235 

 125 



Totals. 



6.277 



36.90 



21.27 



14.67 



13.84 



7.58 



3.74 



1.99 



99.98 



356 

 528 

 41 

 187 

 33 

 14 

 23 



1,182 



30.12 

 44.67 

 3.47 

 15.82 

 2.79 

 1.18 

 1.94 



99.99 



* Derived from Table 3, p. 197 of 1927 Oswego Survey and Table 4 of thii report. 



