PROGRESS IN BIOLOGICAL INQUIRIES, 1937 41 



portant in Green Bay in the spring; of the year (64 percent). The 

 lawyer food consisted of 74 })ercent by volume of fish and 26 percent 

 invertebrates. Dominant items Avere Cottidae (76 percent by volume) 

 in southern Lake Michioan, Coreoonidae (51 percent) and Pontopo- 

 re'/ai (37 percent) in northern Lake Michioan. and Percopsis (34 per- 

 cent) and Mysis (26 percent) in Green Bay. Data were also obtained 

 on the frequency of occurrence of the food items, variation of food 

 with the size of the predator, depth of water, season, and locality; 

 on the number of individual fish of each species destroyed by trout 

 and lawyers; and on the calculated volume of food preceding diges- 

 tion. The lake trout and lawyers are competitors for the same food, 

 and are both predators of the commercially important Coregonidae. 

 The lawyer through its consumption of invertebrates is also a food 

 competitor of the Coregonidae. 



The large number of Cottidae secured from the lake trout and 

 lawyer stomachs made possible a report on the distribution of three 

 species. Gottus cognatus^ Cottiis ricei, and Triglopsis thoinpsonii in 

 Lake Michigan. The number of records previously published from 

 Lake Michigan was surprisingly small because these species are only 

 rarely taken by commercial fishing gear. 



SPECIAL SURVEYS 



Potagannissmg Bay Investigation. — The repeated insistence by 

 sport fishing interests that commercial fishing operations should be 

 prohibited in the Potagannissing Bay area of northern Lake Huron 

 in order to protect game fish led to the passage of a resolution by the 

 Michigan State Senate requesting the Michigan Conservation Com- 

 mission and a representative of the United States Bureau of Fish- 

 eries to conduct an exhaustive survey of the fishery conditions in 

 that region. A preliminary survey was made by Dr. Van Obsten and 

 Fred Westerman of the Michigan Conservation Depai'tment from 

 May 28 to June 2. A program of weekly sampling was instituted 

 and was carried on by conservation officers, to determine the species 

 composition of commercial trap net catches and particularly to ascer- 

 tain how extensively game fish, especially black bass, occur in these 

 nets. Subsequent visits to check the progress of the investigation 

 and to amend the program were made by Bureau representatives dur- 

 ing the periods from July 16 to 21 and August 6 to 10. The investi- 

 gation will be continued' throughout the winter season. Following an 

 analysis of the data, recommendations for the regulation of the fish- 

 eries of the area will be formulated. 



Lake Erie gill net investigation. — In August 1936, the gill net fish- 

 ermen opei-ating in the State of Ohio waters of Lake Erie secured 

 a court injunction which restrained the Conservation Department 

 from enforcing the law regulating the size of mesh in small-mesh 

 nets. The fishermen held that their admittedly illegal nets were not 

 catching more illegal fish than the 10 percent permitted by law-. At 

 the request of the Ohio Conservation Department and the Ohio Gill 

 Netters Association an agreement was made on March 31, 1937, that 

 l^rovided for an investigation by the United States Bureau of Fish- 

 eries. Dr. Deason Avas in the field from April 7 to May 6 and from 

 October 21 to November 6 collecting data on the relationshij:) of the 

 size of blue pike-perch, yellow perch, and saugers and the volume of 



