220 U. S. BUREAU OF FISHERIES 



of each species, changes in age and sex composition of the daily 

 catches, the groAvth rates by_ species and sex, age and size at sexual 

 niatiiiit_y, and the percentage of immature fish in the commercial 

 catch, in addition to these data, precise records are obtained of the 

 total weight, number, and average size of legal and illegal or under- 

 sized fish in each net. and the percentage abundance of illegal fish 

 and game fish. From this it may be seen that an attempt is being 

 made to obtain critical data on the destructiveness of trap nets, bull 

 nets, shallow gill nets, and seines to commercial and game species; 

 on the effectiveness of the present laws on size limits to protect imma- 

 ture fisli ; and on the size of mesh in gill nets and trap nets that is 

 most desirable for commercial fishing — that is, a mesh that will re- 

 tain the greatest number of legal-sized fish with the least destruction 

 to the others. It is hoped that the experiments on the selectivity of 

 me-;hes of various sizes and the work on the size of fish at sexual 

 maturitj^ may form the basis for uniform laws on Lake Erie. 



The State of Ohio is cooperating with the bureau by carrying on a 

 'series of biological studies on the condition of fish life in the lake, 

 making determinations of temperatures, dissolved oxygen, carbon 

 dioxide, nitrogen, hydrogen-ion concentration, plankton, and bottom 

 fauna. In addition, much work was done on the external and internal 

 parasites and on the stomach content (food) of the more important 

 commercial species. As little opportunity has been afforded so far 

 to work up the vast number of data obtained, it is not safe at present 

 to draw any definite conclusions, but rapid progress is being made 

 in the analyses. 



AVISCOXSIX LAKES 



The investigations of the Wisconsin geological and natural history 

 surve^^ on the lakes of northern Wisconsin for the past three years 

 have made possible a study of the growth rates of fishes in relation 

 to the physical, chemical, and biological conditions in the lakes. 

 During the summer of 1927 about 1,800 fish were taken from five 

 lakes that were selected on the basis of limnological diversity. The 

 growth rates of these fish are being studied by the scale method by 

 Stillman Wright, temporary assistant. The food of certain of the 

 species will be studied later. Perch and white suckers make up the 

 bulk of the collection, but the indications at the present are that the 

 Centrarchidse Avill serve better for the purpose of this investigation. 

 Further collecting, particularly of the small fish, will be necessary 

 before the data can be considered adequate. It is hoped that results 

 will be obtained finally that will have a bearing on the problem of 

 planting fish in inland lakes. 



INVESTIGATIONS OF SHELLFISH AND TEREAPIN 



SURVEYS OF OYSTER BOTTOMS 



At the request of the commissioner of the department of game and 

 fisheries of Alabama, a survey of oyster bottoms in Mobile Bay was 

 made in April, 1927, by Dr. P. S. Galtsoff. Oyster-])roducing bot- 

 toms in Alabama are confined to the lower part of Mobile Bay and 

 the eastern part of Mississippi Sound. Because of the different 



