86 BEPORT OF THE SECRETARY OF COMMERCE 



FISHERY INVESTIGATIONS IN INTERIOR WATERS 



Investigations have been conducted on Lakes Michigan and Huron! 

 in the interest of overcoming wasteful and destructive practices of 

 the commercial fisheries, which are responsible to a large degree for 

 the depletion of the more valuable food fishes. An investigation, 

 conducted from a number of Michigan ports on the effects of deep 

 trap nets was completed early in the fiscal year, indicating a con- 

 siderable increase in the use of these nets for catching whitefish, and 

 a wholesale transfer of these nets from certain fishing grounds long 

 famous for their whitefish production to new grounds on account 

 of the depletion of the supply on the former grounds. Illegal-sized 

 fish are most numerous in deep water, hence recommendations have 

 been offered limiting these nets to waters less than 80 feet deep and 

 requiring an increase in the meshes of the lifting pots to permit the 

 escape of undersized fish. 



In Lake Michigan special attention has been given to the effect 

 of chub nets fished on grounds where small lake trout are numerous. 

 It was found that chubs and trout were more abundant in Michi- 

 gan waters where gill nets with larger meshes are employed than 

 in Wisconsin waters. Kecommendations were proposed therefore- 

 for legislation to prohibit or curb the sale of immature lake trout and 

 to provide for an increase in the mesh of nets to protect undersized 

 chubs from unnecessary destruction. The Bureau also cooperated 

 with the Wisconsin Geological and Natural History Survey in a 

 series of limnological and fishery studies in the smaller lakes of 

 northeastern Wisconsin. 



At the close of the fiscal year a manuscript was completed on 

 limnological investigations in western Lake Erie, which were con- 

 ducted during the years 1926 to 1930 in cooperation with various 

 State conservation departments and scientific institutions. This re- 

 port correlates the technical studies of a number of collaborators and 

 presents for the first time in assembled form a great mass of bio- 

 logical and physical data of fundamental importance to the con- 

 servation of the fisheries of the lake. It concludes that pollution, 

 long suspected of adversely affecting the fisheries, is not responsible 

 for the continued decline of the more important species. 



FISHERY INVESTIGATIONS OF THE PACIFIC COAST AND ALASKA 



The Bureau's investigators continued biological observations on 

 the runs of red salmon in Bristol Bay and the Karluk, Copper, and 

 Chignik Rivers in Alaska, in order to safeguard properly the salmon 

 fishery resources of the Territory and to comply with the White Act 

 of 1924. In addition, a study of the age composition of the runs 

 and an enumeration of the spawning fish passing weirs on their way 

 to head-water streams for propagation was made. The final section 

 covering southeastern Alaska of the analysis of statistics of the 

 salmon fisheries has been submitted for publication. 



Heretofore little information has been available regarding the 

 biology of the important runs of pink salmon in Alaska. An in- 

 vestigation has revealed that this species possesses a distinct homing- 



