KEPORT OF THE COMMISSIONER OF FISHERIES. 85 



gether probable that this most higlily esteemed of all catfishes can 

 be propagated successfully in a practical way, by providing a suitable 

 environment and proper nesting conditions, and by the exercise of 

 care to separate the adults from the eggs or young at the proper time. 

 The fry which hatched in the ponds and those which were hatcned from 

 eggs in jars in the experimental battery grew rapidly, attaining n 

 length of 3 inches in a few weeks. 



Other experiments in the propagation and rearing of the large- 

 mouth bass and several species of sunfishes have also been in progress. 



In experiments in the rearing of fishes attention has been given to 

 the study of the food of the developing fishes at aU stages, and to 

 collateral observations of the available food supply. Experiments 

 have also been undertaken in the artificial feeding ot fishes in ponds. 



During the fiscal year a careful biological and fish-cultural survey 

 of certain waters of western North Carolina, including the Mount 

 Pisgah National Forest Reserve, was made and information was 

 gained that will be of material value in guiding the Government's 

 activities in the propagation and protection of fishes in the reserva- 

 tion. 



The fish capacity of artificial ponds or of natural lakes is deter- 

 mined by physical, chemical, and biological conditions, and success 

 in the rearing of fishes or the conservation of fishes will be greater it 

 guided by a proper knowledge of these interrelated conditions. The 

 subject is one of much complexity and knowledge grows only by slow 

 stages and patient apphcation. The Bureau has been glad, therefore, 

 to continue its cooperation with the State Geological and Natural 

 History Survey of Wisconsin, in those fruitful studies of the biological 

 and physical conditions in Wisconsin lakes which have a general 

 application. 



In the study of the fishes in relation to the extermination of mos- 

 quitoes and to public health, as supplemental to the broader investi- 

 gations and activities of the Public Health Service and the Bureau of 

 Entomology, a satisfactory degree of progress has been made and 

 further experiments are undertaken in promoting a growth of desira- 

 ble species of fish in impounded waters. 



WATER-POWER DEVELOPMENT IN RELATION TO FISH LIFE. 



With progress in water-power developments and a steady increase 

 in the number of dams in the course of rivers frequented by migratory 

 fishes, it is unfortunate that there is not more adequate information 

 as to the conditions under which fishways are necessary and practi- 

 cable and the types of fishways adapted for particular species of fish 

 and conditions of stream and dam environment. As much attention 

 as possible has been given to the matter during the fiscal year and a 

 report on the subject was issued. Plans are in contemplation for 

 more extended field studies during the fiscal year 1918. 



The peculiar problems of fish protection in arid regions arise from 

 the fact that large portions of the flow of streams may be diverted 

 into irrigation canals, and, if the fish are permitted to pass freely 

 through the canals and into the laterals, they must eventually be 

 stranded in the fields or otherwise lost. An investigation of the con- 

 ditions in irrigation projects was begun last winter, and a preliminary 

 report on the subject has been made. The investigation has been 

 interrupted for a time by the pressure of other matters. 



