BUEEAU OF FISHERIES XI 



State authorities for modifying the present laws. The successful 

 regulations now in effect on the Alaska beds are the result of similar 

 survej^s. 



INVESTIGATION OF INLAND FISHERIES 



After a general survey of the various problems confronting the 

 fishing industry of the Great Lakes, it was decided to concentrate all 

 activity on Lake Erie, working on a solution of the problem of 

 maintaining its dwindling fisli supply. By means of experiments 

 continued throughout the entire fishing season with both specially 

 constructed and standard commercial gear, particular data are being 

 obtained on their destructiveness to both commercial and game species, 

 on the effectiveness of the present laws on size limits in protecting 

 immature fish, and on the most desirable sizes of mesh to be recom- 

 mended for commercial use in both traps and gill nets. Further 

 observations are being made on the migrations of the fish, their rates 

 of growth, age at maturity, and similar facts in their life history. 

 In this undertaking the bureau is receiving excellent cooperation 

 from other agencies, particularly the State of Ohio. Plans for fur- 

 ther cooperation were made and an extensive program of investiga- 

 tion, with practical bearing on the fisheries, was undertaken before 

 the close of the fiscal year. 



For a number of years the bureau has cooperated with the Wis- 

 consin Geological and Natural History Survey in limnological studies 

 of certain lakes in northern Wisconsin, and in addition has under- 

 taken a study of the factors influencing the growth of fish in various 

 lakes of diverse character. 



Work at the Fairport (Iowa) laboratory is concerned chiefly with 

 the artificial propagation of fresh-water mussels, studies on the pond 

 culture of fresh-water food fishes, and the development of the fish 

 resources of the Upper Mississippi AVild-Life and Fish Refuge. The 

 extremely important experiments in rearing the larval fresh-water 

 mussels in nutrient solutions in the laboratory, thus eliminating the 

 parasitic stage in the life history of these animals, were continued 

 and perfected during the summer of 1927, and large-scale experiments 

 on the production of young mussels in ( ommercially s"o-nificant quan- 

 tities were undertaken during the summer of 1928. The program of 

 surveys of mussel-supporting areas has been continued and close 

 cooperation had with the conservation commissions of several States 

 in perfecting the regulations governing the taking of mussels. 

 Studies of the rate of growth are being made in order to determine 

 the most productive areas where mussel farming can be developed 

 and to judge the success of the system of areas closed to commercial 

 operations. 



A study is also being made of the aquatic resources of the Upper 

 Mississippi Wild-Life and Fish Refuge area to determine the amount 

 ancl character of life suitable for fish food and the kinds of fish with 

 which the refuge should be stocked for breeding purposes. 



OYSTER INVESTIGATIONS 



03^ster investigations covered four main lines of research, namely, 

 a study of oyster bottoms, study of factors controlling spawning and 



