370 U. S. BUEEAU OP FISHERIES 



fish. This new type of gear, which was introduced into Lake Huron 

 in 1928, proved so very effective and its use expanded so rapidly 

 during the succeeding years as to create grave fears concerning the 

 future of the fishery. The Bureau's statistical data based on a 

 study of the Lake Huron fisheries by geographical districts and over 

 a period of 5 years, showed these fears to be well grounded. Ac- 

 cording to the Bureau's data, the history of the deep trap net fishery 

 in a single fishing district may be described approximately as fol- 

 lows : The introduction of the deep trap net into a fishing area is 

 followed by an immediate rise in whitefish production to a point 

 far above the normal. This increased production continues over a 

 period of 2 years, although a drop in the catch per unit effort may 

 be detected in the second year of the use of the trap net. The third 

 year sees a marked drop both in total production and in catch per 

 unit effort. 



The statistical evidence supplied by the Bureau that the use of 

 the deep trap net occasions a rapid and severe depletion of the white- 

 fish stock was directly instrumental in the securing of legislation 

 regulating and restricting the use of this destructive gear. The pub- 

 lication of a complete report on the statistics of the commercial fish- 

 eries of Lake Huron is being delayed pending the analysis of the 

 1934 material. 



PIKE-PERCHES 



The racial and life history study of the three species of pike- 

 perches {Stizostedion) of Lake Erie with which H. J. Deason has 

 been occujDied has progressed toward completion. Scale samples from 

 8,390 fish (2,812 yellow pike-perch, 3,441 blue pike-perch, and 2,137 

 saugers) have been mounted, aged, and measured during the course 

 of the study. Lengths to the end of each year of life and annual 

 increments of growth have been calculated and summarized in tabular 

 form. Some conclusions of this work were given previously (Prog- 

 ress in Biological Inquiries, 1933), in which only a portion of the 

 above material was employed. 



Because of the necessity of correcting certain fundamental errors 

 inherent in the application of the scale method of growth determina- 

 tions to pike-perches, it was found desirable to devote some time to 

 the basic assumptions of the scale theory insofar as they applied to 

 these species of fish. This study dealt largely with the variations 

 involved in the proportionate growth of the body of the fish and its 

 scales. As a result of this study it was possible to secure more accurate 

 data on the rate of growth of the various species. 



The racial study of the pike-perches is concerned with the syste- 

 matic relationship between the blue and yellow pike-perches, princi- 

 pally those of Lake Erie. A total of 1,038 preserved specimens have 

 been examined and measured, which number is made up as follows : 

 449 blue pike-perch from Lake Erie, 52 blue pike-perch from Lake 

 Ontario, 230 yellow pike-perch from Lake Erie, and 307 yellow pike- 

 perch from Saginaw Bay in Lake Huron. The Lake Ontario and 

 Lake Huron materials were employed in order to study the variation 

 in a single species from different bodies of water. At the beginning 

 of this study some 30 counts and measurements were made on each 

 fish, but as the work progressed and it became increasingly evident 



