120 U.S. BUREAU OF FISHEEIES 



period, April 5-20, 1932, biological data and scales were secured from 

 some 1,329 yellow pike perch, 1,924 saugers, and 133 yellow perch 

 from Lake Erie — a total of 3,386 fish. These data were necessary to 

 complete the series collected in previous years and to make possible 

 a study of the complete life history of the pike perches of Lake Erie. 

 Limnology. — No field work was done in 1932 on the limnology of 

 Lake Erie, but Dr. Stillman Wright was assigned to the compilation 

 of the large amount of data collected by the cooperative survey (see 

 report for 1931), and to the preparation of the final report which is 

 now nearly ready for submission for publication. 



COOPERATIVE INVESTIGATIONS, INTERIOR LAKES OF 

 WISCONSIN 



In the cooperative investigations of the physical and chemical 

 conditions in lakes of northeastern Wisconsin conducted by the Wis- 

 consin Geological and Natural History Survey and the Bureau of 

 Fisheries the very active program of investigation by the personnel 

 of the State Survey was conducted by a field party of 11 biologists 

 and chemists under the direct supervision of Dr. A. E. Birge and 

 Prof. Chancey Juday at the Trout Lake Laboratory from June 27 to 

 September 12, 1932. A study of fish life in these lakes was conducted 

 by Dr. Ralph Hile and one assistant for the Bureau of Fisheries. 



Materials obtained for the study of the age and growth of the fishes 

 of the lakes of northeastern Wisconsin included data from 8,007 

 specimens. Of this number 1,407 ciscoes, 724 perch, and 329 rock 

 bass were preserved. The preserved ciscoes are being used in a mor- 

 phometric study bearing on changes of form with growth and on the 

 question of the existence of local races of that species. The need of 

 more exact formulas for the calculation of growth of the perch and 

 rock bass from scale measurements has made necessary a detailed 

 study of the change of thef body-scale ratio with increase in age and 

 size. The collections were again taken from the six lakes selected 

 as "types." 



With the 1932 collections of age and growth materials pertaining 

 to the perch, cisco, and rock bass, the field work of this phase of the 

 cooperative study of the lakes of northeastern Wisconsin is completed. 

 Reports by Dr. Hile of the Bureau on the age, growth, and morphorn- 

 etry of the cisco and by Edward Schneberger of the Wisconsin 

 Geological and Natural History Survey on the age and growth of the 

 perch will be completed in the near future. 



In general, the major part of the Hmnological investigations con- 

 ducted by the Geological and Natural History Survey was done on 

 the six lakes which were selected for an intensive study of the fish 

 fauna, with the exception of observations on the penetration of solar 

 radiation into the various lake waters; several other lakes were 

 included in the latter investigations. 



In the chemical work, quantitive determinations of the dissolved 

 gases, phosporous, nitrates, and hydrogen-ion concentration were 

 made on the 6 lakes from which fish were obtained for growth studies 

 •and 2 additional lakes. No noteworthy chemical changes from pre- 

 vious years were observed in these lakes. 



A special study of the hydrogen-ion concentration of the water was 

 made in a number of lakes. There was a question regarding the 

 reliabiUty of the pH readings on samples obtained from the deeper 



