584 U. S. BUEEAU OF FISHERIES 



in the summer of 1930. Dr. Ralph Hile of the Bureau of Fisheries 

 and Edward Schneberger of the University of Wisconsin made col- 

 lections of fish scales for age studies during the months of July and 

 August and most of September, obtaining data from a total of 

 4,921 fish. 



The collections of three summers have made available for growth 

 study, material from approximately 12,000 fish. The forms most 

 numerous are the perch, cisco, rock bass, bluegill, and sucker. There 

 are also included 1,175 game fish — muskellunge, pickerel, i)ike perch, 

 and black bass. A large part of the game fish have been furnished 

 by sport fishermen who are supplied with packages of scale enve- 

 lopes, along with directions for taking the desired data. 



The study of the growth of the perch and the game fish is being 

 made by Mr. Schneberger, while Doctor Hile is investigating the 

 rock bass, bluegill, and cisco. In the past, collections have been made 

 from a considerable number of lakes, but it is planned, in the future, 

 to concentrate efforts on a few selected typical lakes, so that atten- 

 tion may be given to growth problems of a more special nature. 



LIMNOLOGICAL STUDIES 



Investigations were continued on the lakes of northeastern Wis- 

 consin during the summer of 1930 by the Wisconsin geological and 

 natural history survey. The Trout Lake laboratory of the survey 

 was opened on June 20 and work was continued until September 15. 

 These studies are entirely supervised and largely financed by the 

 survey, but in recognition of the bureau's modest cooperation the 

 following report has been submitted by Prof. Chancey Juday, and 

 because of its intimate relation to other undertakings by the bureau 

 is published here. 



The field party consisted of E. A. Birge, C. Juday, Edward Schneberger, 

 Hugo C. Baum, J. P. E. Morrison, Ruby Bere, J. B. Goldsmith, C. A. Herrick, 

 biologists, and Frederick J. Stare and Theodore Setterquist, chemists. Dr. 

 Ralph Hile of the U. S. Bureau of Fisheries also was at the laboratory in co- 

 operative work on the fish problem. During the month of August, W. L. Haf- 

 ner of Armour Institute, Chicago, was employed in connection with hydro- 

 graphic surveys of a number of lakes. 



The field studies included such items as hydrographic survey of 20 lakes, the 

 tempei'ature, transparency, color, the conductivity of the water and the rate 

 at which the sun's energy is absorbed by the water in different types of lakes. 

 The chemical determinations consisted of hydrogen-ion concentration, free and 

 fixed carbon dioxide, dissolved oxygen, oxygen consumed, and calcium. The 

 biological phases of the work consisted of quantitative studies of the net and 

 centrifuge plankton, a further study of the aquatic Mollusca of the district, 

 the leech fauna of a number of lakes, the collecting of fish for growth studies, 

 and a study of the external parasites of the fish. 



In the hydi'ographic work, 20 lakes were surveyed and sounded. The area 

 and volume of 19 of these lakes have been determined so far. The contours 

 of Trout Lake are very complicated and the measurements and computations 

 on it have not been completed. The area of the other lakes ranges from 1.2 

 to 230 hectares and the volume from 06,780 to 23,302,000 cubic meters. The 

 determination of the volumes of these lakes makes it possible to ascertain 

 approximately how much organic matter and dissolved salts are contained in 

 the entire body of water. 



The work was extended to 50 new lakes in the district during the summer ; 

 this makes a total of 529 lakes that have been visited in the six summers 

 (1925-1930) that the investigation has been in progress. This completes the 

 general survey of the more important lakes of this region, and it is now the 



