PROGRESS IN BIOLOGICAL INQUIRIES, 192 9 1089 



Chemical observations show that pollution is not at present a 

 serious menace to the fishery, being limited to the vicinity of the 

 few large cities. Biological observations confirm the findings of the 

 previous year's work and indicate that the natural production of 

 small organisms, both plant and animal, upon which the fish life 

 depends is adequate to support a much greater adult fish population 

 than at present exists in the lake. 



Although there is a considerable amount of valuable information 

 on the adult fish of Lake Erie, little attention had been given 

 previously to the survey begun in 1928 to the larval and early stages 

 of development of the various fishes. The newly hatched fish seldom 

 resembles its parent in external appearance, so that careful study was 

 necessary to identify and describe the considerable number of species 

 taken in the juvenile and laical stages. At the close of the sum- 

 mer's work, 14 species were described and figured, making it possible 

 to follow the life histories of the more important forms with relative 

 completeness. 



When the technical data collected in the course of this survey 

 are fully analyzed and the combined reports published, a sound foun- 

 dation will be afforded for more exact studies of the commercial 

 fishery and for an understanding of the movements and habits of the 

 various food fishes now believed to be suffering from overfishing. 



STUDIES IN WISCONSIN LAKES 

 GROWTH OF FISHES 



The investigation of growth rates of fishes in lakes of northern 

 Wisconsin, carried on by the bureau in 1927 and 1928, has been dis- 

 continued ; and the Wisconsin Geological and Natural History Survey 

 has taken over the problem. No fish were collected in 1929, but the 

 scales taken in the previous years are being studied in the laboratory 

 of the survey at the University of Wisconsin. 



The results of the investigation of the rock bass have been re- 

 ported in a recently published report. The paper may be summa- 

 rized as follows : The growth curve of the rock bass, as indicated by 

 a study of scales of fish from Trout and Muskellunge Lakes, Vilas 

 County, Wis,, typically has the double sigmoid form. The rate of 

 growth in the second period of rapid growth is greater than that in 

 the first. The first period occurs in the first year and the second in 

 the fifth year. More individuals grow most rapidly in the fifth 

 year than in any other ; the second largest number grow most rapidly 

 in the sixth year, and the third largest number in the fourth year. 

 The rock bass of collections from Muskellunge Lake made in 1927 

 and 1928 grew at approximately the same rate. These collections 

 were made in the same general locality and are regarded as repre- 

 senting a single population. Rock bass taken from Trout Lake in 

 1927 showed a much more rapid rate of growth than those taken in 

 1928. The two collections were made in different localities and are 

 regarded as representing tw^o distinct populations, each with a char- 

 acteristic rate of growth. In comparing the two lakes for these 

 years, it was found that in 1927 the rock bass of Trout Lake showed 

 a more rapid growth rate ; while in 1928 the condition was reversed, 

 with those in Muskellunge Lake showing the greater development. 



