PROGRESS IN BIOLOGICAL INQUIRIES, 1923. 



25 



will continue to be held, however, in anticipation that at some future 

 time they may ripen and spawn. This species is of particular value 

 commercially, and its perpetuation is a matter of concern in view of 

 the gvent decrease in its numbers in recent years. Experiments in 

 the culture of the channel catfish have been continued. Considerable 

 light has been thrown on the natural history and essential factors for 

 success in the pond culture of this species, and several ponds have 

 been set aside for a practical demonstration of these experiments. 

 At the close of the fiscal year quite a number of nests were observed, 

 and it seems quite possible that the pond culture of this fish may be 

 taken up on a practical basis next year. An effort at the pond cul- 

 ture of the hackleback sturgeon was made at the Fairport station 

 and a large mass of data was collected, on which it is hoped to base 

 recommendations for protective legislation for the species. The 

 fishery for this species is of value and one that is carried on inten- 

 sively l)ecause of the high prices paid for both the flesh and the eggs. 

 Observations on the production of the " farm pond " at Fairport 

 have been continued Avith significant results. The purpose of the 

 study of this j^ond production has been to obtain useful data regard- 

 ing the possible value of small ponds on farms or large estates. With 

 this end in view the pond has been handled just as one would be 

 managed in practice; that is, the fish have not been fed but have 

 depended on the natural " fish food," the small animals and plants 

 that normally form the diet of food fishes and that are naturally 

 produced in the pond. 



Tlie production of the pond has been obtained by computing the 

 difference between the weight of the fish at the time of their intro- 

 duction into the pond in spring and the weight of the same fish and 

 their offspring as occasionally caught out during the summer or 

 when removed from the pond at the autumn inventory. This method 

 of computation gives the increased weight of fish in the pond due 

 to the " turnover " of small plants and animals. The fish used (the 

 bluegill) feeds primarily on insect larvae, cladocerans, copepods, and 

 plants. This annual net " turnover " of food organisms of the pond 

 into fish flesh is here tabulated. The table includes also the weight 

 of the fish of edible size taken from the pond. 



The annual production of fish of edible size in 1919 and 1920 was 

 based on the weight of fish removed from the pond by hook and line 

 during the summer. In 1921 and 1922 line fishing was not carried 

 on in the pond and the data on the production of edible-sized fish were 

 collected when the fall inventory was made. The use of the fall 

 measurements for this computation necessarily tends to hold down 

 the total possible "turnover" and the total possible production of 

 fish of edible size. The computation, however, as made for 1921 

 and 1922, can not be far from accurate, though the total net " turn- 



