192 Conservation Department 



IX. A QUANTITATIVE STUDY OF THE FISH FOOD 

 SUPPLY IN SELECTED AREAS 



By P. R. Needham, 

 Instructor in Limnology and Ecology, Cornell University 



The immediate purpose of these studies was to determine, as far 

 as possible, the relative amounts of fish food available in different 

 types of stream conditions, an important consideration in the de- 

 velopment of a stocking policy. Further, it was desirable to be- 

 gin research work on a few main problems in trout culture under 

 wild conditions which could be carried on from year to year, 

 the results, as obtained, being applied toward improvement of 

 fishing conditions. 



The following problems were selected for study: 



1. Relation of width of stream to quantity of primary food 

 organisms. 



2. Relation of types of bottom to quantities of food. 



3. Amounts of terrestrial food animals which fall into the 

 water and probably serve as food for trout. 



4. Comparison of quantities of available food found in 

 various types of submerged plant beds. 



By designating the animals found in streams as "available" 

 food, it is meant that while some of the animals may not actually 

 be eaten by trout, nevertheless they are present in streams and 

 represent possible or potential foods which could be eaten if the 

 trout desired. In quantitative studies, in order to establish aver- 

 ages with a low probable error, much data must be available as a 

 working basis. In these studies, with limited time, insufficient 

 figures were obtained with which to calculate true averages and 

 hence the probable error is doubtless greater than if more figures 

 had been available. Therefore it seems, desirable to consider these 

 results as tentative until further work can be done and to con- 

 sider this in the nature of a progress report.* The summer sea- 

 son of three months from June 15 to September 15 was devoted 

 to the study of these problems. 



These results having entirely to do with potential or available 

 food as it is found in the streams in this vicinity, should in future 

 studies be correlated with the actual food of trout under these same 

 conditions to determine what foods are actually turned into fish 

 flesh and the proportionate amounts of each. Once this knowledge is 

 gained, it will be possible to work towards increase of natural 

 foods under wild conditions. 



* Lack of space did not permit insertion of full proof of all statements and 

 description of apparatus and methods used. This can be found in the files 

 of the N. Y. State Conservation Department and in the Limnological Labora- 

 tory of Cornell University. 



Mr. Deleon Walsh worked with the writer during the entire period both in 

 the field and in the laboratory. 



