PROGRESS IN" BIOLOGICAL INQUIRIES, 1931 467 



DEEP TRAP NETS OF LAKES HURON AND MICHIGAN 



A new cooperative investigation, separate from that on the chub 

 net, was started with the States of Michigan and Wisconsin on the 

 deep trap nets. In June, 1929, the deep trap net was introduced in 

 Lake Huron at Port Hope, Mich., primarily for the purpose of tak- 

 ing whitefish. During the past two years this type of gear has 

 spread very rapidly throughout Lake Huron and upper Lake Michi- 

 gan, including Green Bay. A deep trap net is virtually a submerged 

 pound net, since it has lead, a heart, a tunnel, and a pot or crib. 

 The crib where the fish are finally captured is entirely inclosed so 

 that the entire net can be completely submerged. The crib varies 

 from 18 to 35 feet in depth, 30 to 40 feet in length, and in width 

 usually tapers from 24 feet at the front to 20 feet at the back, and 

 the lead varies in depth from 25 to 45 feet. This net is usually 

 fished at depths varying from 60 to 125 feet, although it can be 

 fished at greater depths. 



The principal criticisms heard regarding deep trap nets are that 

 they take too many adult whitefish, thereby depleting the stock in 

 the lake and glutting the market, and that they destroy too many 

 undersized fish. The States of Michigan and Wisconsin and the 

 fishermen are deeply concerned about the rapid spread of these nets 

 throughout the Great Lakes and have therefore urged the bureau to 

 make a study of their action upon the fish stock. The patrol boats 

 of the conservation departments of both States were placed at the 

 bureau's disposal in the preliminary surveys. 



The survey in AVisconsin waters was completed during the period 

 July 6 to 16, 1931, and a repoi't, including a set of recommendations, 

 was submitted by the joint commission. The survey in Michigan 

 waters was carried on from July 24 to October 21, 1931, out of the 

 following ports: Bay Port, East Tawas, Oscoda, Ossineke, Alpena, 

 Rogers City, Cheboygan, Epoufette, Naubinway, Manistique, and 

 Fairport. The Conservation Department of Michigan furnished one 

 assistant for this work and all transportation. In view of the great 

 importance of the study and of the many complications involved, 

 it has been deemed advisable to continue the investigation another 

 year before drawing up final recommendations. 



STUDIES IN LAKE ERIE 



Fishery investigations. — The spring of 1931 saw the completion 

 of our experimental fishing with trap nets on Lake Erie begun in 

 the fall of 1927. The report for 1930 referred to the study of the 

 fishing characteristics of one of our experimental trap nets. This 

 particular study was carried on at Lorain, Ohio, in 1930 for various 

 species of fish, excluding the sauger, a species relatively unimpor- 

 tant in the commercial catch at Lorain. Since the only remaining 

 principal objection of the commercial fishermen to the introduction 

 of our experimental trap net for commercial fishing on Lake Erie 

 was that too many legal saugers would be released by it (it is asserted 

 that the sauger is the most active of the Great Lakes commercial 

 species of fish and would escape from a net which would retain other 

 less active species), it was deemed desirable to resume the experi- 



