PKOGRESS IN BIOLOGICAL INQUIEIES, 1921. 



21 



awarded a prize by the American Fisheries Society as the most 

 important contribution in the application of biological science to the 

 advancement of fish culture. A series of practical experiments based 

 upon these results was conducted during the winter at one of the 

 fish-cultural stations of the Bureau. Just before the close of the 

 year they were transferred to another station where more adequate 

 facilities were available, and it is planned to continue them during 

 the coming fiscal year that definite results may be obtained. 



i^ITNNOW^S IN RELATION TO FISH CULTURE. 



The smaller members of the minnow family are important to fish 

 culture since they represent a primary source of food for more than 

 20 of the larger food and game fishes. The success of the introduc- 

 tion of game fish into streams or ponds necessarily depends to no 

 small extent upon the suitability of the stream or pond for the sup- 

 port of minnows. Hence the budget of knowledge requisite for 

 efficient fish culture includes information regarding the food and 

 other requirements of minnows. Therefore, while the study of min- 

 nows by C. M. Breder and D. R. CraAvford, scientific assistants, was 

 conducted almost entirely outside of office hours and represents a by- 

 product as it were, the results gained are of practical value. 



They studied six common species in the ^dcinity of the District of 

 Columbia ; chub minnow, Seiiiotilus huUaHs; red-bellied dace, Leucis- 

 cus V andor sails ; Notropis procne; shiner or red fin, Notropis cor- 

 nutus; black-nosed dace, Rhinichthys atronasus; cutlip, Exoglossuui 

 maxillingua. All were found to be predominantly carnivorous, in- 

 sects forixdng the bulk of the food taken, although two species, 

 Notropis procne and Exoglossum maxiUingua^ consumed much vege- 

 table matter. Various worms, filamentous algse, and diatoms entered 

 into the food in considerable quantities. These minnows are, there- 

 fore, in direct competition with the young of important game fish 

 and may even prey upon the fry of them. It is suggested, therefore, 

 that if minnows are introduced into ponds as food for game fish, 

 discretion should be exercised regurding the use of larger and more 

 rapidly growing minnows, such as the chub minnow and red fin, which 

 may outstrip young trout in growth and under some circumstances 

 become a menace rather than a benefit. 



In all cases the suitability of the introduction depends both upon 

 the species of minnow and upon the species of fish which is to be 

 fostered, as well as upon other conditions prevailing in the water and 

 upon the degree to which the various factors are under the control 

 of the fish culturist. Minnows seem to thrive best in streams or 

 ponds where the banks bear overhanging vegetation that supports 

 an abundance of insect life. Where this condition prevails there is 

 probably less likelihood that the minnows will prey upon the eggs 

 or young of other fishes. 



A NEW FORM OF POND OUTLET. 



Practical success in fish culture depends in no little measure upon 

 economy in construction and operation of the pond and upon the 

 convenience with which it can be drained for removal of brood stock 

 or young, elimination of enemies, cleaning the bottom, or removing 

 obnoxious plants. The concrete- box outlets commonly used are not 



