1923 ENTOMOLOGICAL SOCIETY. 27 



deduction, therefore, that the insects of Lake Nipigon as food for whitefish were 

 worth half this amount, namely $81,000. The Chironomids would contribute 

 $56,000. 



If the whitefish in all lakes feed upon insects in like proportions, then we 

 have these figures for the Province of Ontario in 1919: 



Total catch whitefish 6,625,304 lbs. 



Value at 10c. per lb $662,530.00 



Value of the insects as food $330,000.00 



Value of the Chironomids .' $230,000.00 



These calculations appear to be reasonable and are not essentially different 

 from those used by stockmen. Cattle are fed certain feeds in definite ratios 

 and later are sold at a certain amount per pound. The feeds have been worth 

 to the stockman the amount which he obtains, from his sale of steers. There 

 is this difference between the two cases, however, in that the food crop for the 

 fish has cost the fisherman absolutely nothing, whereas the food-stuffs, for the 

 cattle have cost the stockman a considerable sum. Some day. when aquiculture 

 has advanced along lines similar to those of agriculture the fisherman may 

 pay more attention to his crops of food-stuffs. 



Do the results of our investigation of the occurrence of the food animals 

 on the bottom of Lake Nipigon correspond with the results of the examination 

 of the stomach contents of the whitefish? During the summer of 1921, Messrs 

 Adamstone and Harkness operated a small Ekman dredge and obtained bottom 

 samples in various parts of the lake in depths from two to 275 feet.* The area 

 of bottom brought up was 81 square inches, and the animals in this area were 

 sifted out, classified and counted. They found the following average number 

 -of animals per square yard, irrespective of depth: 



Chironomidag Shrimps Pontoporeia Snails, etc. Mayflies 



256 144 128 16 



At this rate there would be for the whole lake in the neighbourhood of 

 1200 billion Chironomid larvae, which on the basis of calculations used by 

 Richardsonf for the Illinois river, would amount to about 100 million pounds 

 or about 100 pounds per acre of bottom. Further, using the ratio of five pounds 

 of food to one pound of fish as developed by certain European investigators, 

 whose publications the writer has not seen but which are referred to by Richard- 

 son (loc. cit.), it is evident that the Chironomids alone occur in numbers suffi- 

 cient to support a very large fish population. 



The bottom inhabiting insects form one of the most important sources 

 of food supply for bottom-feeding fish such as the whitefish. Here is a crop 

 which grows without cost of money, time or labour on the part of man and of 

 which very few people, very few fisherman especially, have any appreciation. 

 In our investigation we are trying to get at all the facts concerning this crop, 

 especially the factors which have to do with its development, and some day we 

 may be able to develop methods for exerting some measure of control. It is 

 apparent from the data already at hand, that the crop should be very carefully 

 protected from destructive industrial wastes and from any smothering materials. 



*For complete account see forthcoming report by Messrs. Adamstone and Harkness, in 

 University of Toronto Studies, Publications Ont. Fish Research Laboratory. 



fRichardson, Robert E. The Small Bottom and Shore Fauna of the Middle and Lower 

 Illinois River and its connecting Lakes, Chillicothe to Grafton, its Valuation, its Sources of 

 Food Supply and its Relation to the Fishery. Bull. Nat. Hist. Survey Illinois, vol. XIII, 

 article XV. 



