118 REPORT OF THE SECRETARY OF COMMERCE 



an accurate measure of the abundance of certain species, studying the 

 effect of various types of gear in commercial use, and supplying tech- 

 nical advice to aid State officials in the framing of commercial 

 fisheries regulations. 



An investigation was conducted on Lake Erie to determine the 

 relation between the mesh size of gill nets and both the volume of 

 the catch and the size of individual fish taken. On the basis of these 

 and earlier gill-net studies, the Bureau will recommend a definite 

 mesh size for gill nets used for all species commonly taken in small- 

 meshed nets, and will recommend also an upward revision of present 

 legal size limits for blue pike-perch and saugers in order to provide 

 better protection for spawning females. 



Because of the legal provision that net mesh must measure full size 

 at all times, an investigation was carried out to determine the allow- 

 ance that should be made for shrinkage. The differences among 

 various methods of measuring gill-net meshes are also being deter- 

 mined experimentally. These two investigations will provide for 

 more effective operation of the fundamental conservation measure of 

 net regulation. 



During the year a survey was made to determine the effect of com- 

 mercial fishing on the game fishes of the Potasannissing Bay area. 

 The findings will be made the basis of recommendations for the 

 regulation of the fisheries. 



Progress was made in compiling and analyzing the extensive col- 

 lections of data from earlier years. These included a complete analy- 

 sis of statistics of commercial fisheries of Great Lakes waters under 

 jurisdiction of the State of Michigan, providing records of fluctu- 

 ations in fishing intensity, yield, and abundance of important com- 

 mercial species over an 8-year period; a study of the whitefish 

 fisheries of Lake Michigan and Lake Huron; and a comprehensive 

 report on the investigation of Lake Champlain fisheries conducted by 

 the international fact-finding commission in 1930 and 1931. 



Life history studies of the yellow perch and Lake Erie whitefish 

 were resumed and studies of the competitive food habits of lake trout 

 and lawyers were completed, the conclusion being reached that both 

 species are predators of the commerciall}^ important whitefish family, 

 and that the lawyer through its consumption of invertebrates is also 

 a food competitor of the whitefish. 



Important advances made during the year in State administration 

 of the fisheries were the adoption of the flexible rule method of measur- 

 ing gill-net meshes by four Great Lakes States and the Province of 

 Ontario, and the passage of a discretionary power act by the Wisconsin 

 Legislatiu'e, empowering State conservation officials to enact commer- 

 cial fisheries regulations by decree. 



AQUICULTURAL IN\'ESTIGATIONS 



Although the yearly output of fresh-water game fishes by State 

 and Federal hatclieries amounts to several billion young fish, it is 

 generally recognized that a commensurate return is not being realized 

 by the several million anglers who seek sport in the Nation's streams. 

 The conclusion is inescapable that some, at least, of the hatchery output 

 is being wasted by being planted under conditions which do not favor 

 survival. Scientific investigations beino; conducted in the field of 



