REPORT OF THE COMMISSIONER OF FISHERIES. 19 



FISH-CULTURAL EXPERIMENT WORK. 



The experimental work in tlie interest of fish culture, both public 

 and privtite, which is pursued primarily in connection witii the 

 fisheries biological station at Fairport, Iowa, has been continued as 

 far as permitted by the available means and personnel. The in- 

 vestigations of previous years have yielded results which it has been 

 possible to apply in practice at several of the Bureau's fish-cultural 

 stations, and the advantages to accrue from a more aggressive pur- 

 suit of fish-cultural experiment work are undoubted. It is therefore 

 to be regretted that provision has not been made for the special per- 

 sonnel without which it is impossible to make adequate progress. 



The experiments at Fairport, which relate to the propagation of 

 bass, sunfish, catfish, and butFalofish in ponds, are supplemented by 

 investigations of the plants and lower animals which live in the 

 ponds and contribute directly or indirectly to the food supply of 

 fish and to the yield of fish from the ponds. Results of special 

 interest and value are regularly obtained, and if the observations 

 could be more widely extended the Bureau would rapidly gain in 

 ability to furnish just the sort of helpful information desired by the 

 amateur fish-culturists in all parts of the country w'ho are seeking 

 to improve the conditions of home life on the farm by developing 

 the fishpond as a source of food and a means of recreation. 



MOSQUITO CONTROL BY THE USE OF FISH. 



Previous reports have stressed the public service rendered by the 

 Bureau in conducting investigations and practical operations in the 

 employment of fish as a means of exterminating mosquito larvae 

 under conditions where other means of control are either imprac- 

 ticable or unnecessarily expensive. Renewed assurance of the value 

 of this work was gained during the past year when the Bureau of 

 Public Health Service urgently requested this Bureau to detail an 

 assistant for full time in advising with Federal, State, and local 

 health officers in the proper use of fish in the broad antimalaria cam- 

 paign in the Southern States. There have also been several freely 

 offered expressions of appreciation for the value of this service from 

 State health officials. 



The studies of fishes and other aquatic animals in relation to mos- 

 quito control have not been restricted to southern waters, but addi- 

 tional experiments have been conducted in Northern States, notably 

 in the Interstate Palisades Park of New York and New Jersey. 



STUDY OF FISH DISEASES. 



While the Bureau was without a regular fish pathologist during 

 the first half of the fiscal year, the study of the parasites and dis- 

 eases of fishes was continued during most of that period by the aid 

 of temporary employees. Diseases of fish in the St. Lawrence 

 River and in certain fish hatcheries were investigated, and appro- 

 priate remedies were suggested when practicable. Later in the year 

 systematic researches were directed at such special problems as' the 

 widely prevalent " white-spot " disease in salmonoid eggs and the 

 mortality of pike-perch eggs which substantially lowers the efficiency 

 of all pike-perch hatching operations. 



