EEPOKT OF THE COMMISSIONER OF FISHERIES. 19 



These studies have inchided the systematic rehxtionships of the 

 several species, their distribution, life histories, and habits, rate of 

 growth, ages at maturity, and maximum size, etc. Certain of these, 

 particularly the age at maturity, appear to be subject to local varia- 

 tion. It is expected that a report embracing facts of value to fish 

 culture and serving as a basis for rational conservation measures will 

 be practically completed during the next year. 



Owdng to the great importance of the fisheries of Cliesapeake Bay, 

 the decline in numbers of certain important food fishes, the ease 

 with which some of them can be intercepted and captured, and the 

 fact that the waters of the bay are under the jurisdiction of two 

 States that can not always reconcile their conflicting interests, it 

 appeared important to undertake an investigation of the fishes in 

 order to furnish information to those responsible for their conserva- 

 tion. The field work was begun near the end of the last fiscal year 

 and has now been brought practically to a close. The study of col- 

 lections and valuable notes and records accumulated has made some 

 progress. The fishermen have evinced appreciation of the practical 

 value of this work and have cooperated freely in supplying speci- 

 mens and information and in giving access to fishing records. 



Primarily as an incident to other duties, certain of the bureau's 

 workers have been able to make material additions to knowledge of 

 fresh-Avater fishes of economic value. In particular the information 

 obtained concerning the natural history of the rock sturgeon is of 

 importance in the formulation of measures to protect that valuable 

 fish, which is yearly becoming less abundant. 



Largely by volunteer cooperation with the faculty and graduate 

 students of the University of Wisconsin, useful studies have been 

 made of the food and feeding habits of certain fresh-water fishes. 



INVESTIGATIONS RELATING TO FISH CULTURE. 



The experiments in pond culture of the buffalofish that have been 

 ■conducted at Fairport (Iowa) station for several years have demon- 

 strated that while not entirely necessary it is definitely advantageous 

 to cause a rise in the water level of the pond at the spawning time, 

 thus simulating by the production of an "artificial flood" the con- 

 ditions that prevail at the annual rise of the streams of the Missis- 

 sippi Valley. In a pond used in the experiments the progeny of 

 eight fish at the end of the season numbered 98,000 fingerlings from 

 2 to 5 inches long, a product equivalent to a yield of about 1 ton of 

 fish to the acre. A paper on the pond culture of buffalofish, one of 

 the most important food fishes of the Mississippi, has been prepared 

 for the instruction of owners of ponds desiring to raise fish for home 

 or local consumption. 



The beneficent and maleficent, relations of aquatic insects to pond 

 culture w^as continued as a useful subject of investigation during 

 the year. The life histories of nine species of beetles and bugs were 

 worked out, and methods of control of the undesirable species have 

 been indicated. 



At the request of the Iowa State Game and Fish Commission an 

 examination was made of Clear Lake, Iowa, which resulted in recom- 

 mendations toward the development of a commercial fishery for 

 ^' rough " fish, the propagation of game fishes, and the general man- 

 agement of the water area in the interest of increased fish production. 



