1090 U. S. BUREAU OF FISHERIES 



LIMNOLOGICAL STUDIES 



Limnological investigations on the lakes of northeastern Wisconsin 

 were continued during the summer of 1929 in cooperation with the 

 Wisconsin Geological and Natural History Survey. The Trout 

 Lake laborat<iry of the survey was opened on June 21, and work 

 was continued until September 10. 



The held party consisted of E. A. Birge, Chancey Juday, W. L. 

 Tressler, Mrs. W. L. Tressler, J. P. E. Morrison, Edward Schne- 

 berger, Hugo C. Baum, biologists ; Frederick J. Stare and F. Lowell 

 Taylor, chemists. In addition chemical analyses of residues obtained 

 hj evaporating 3 or 4 liters of water, were made by C. H. Winning, 

 T. F. Setterquist, and P. C. Cross, the work being done in the chem- 

 ical laboratory of the University of Wisconsin. 



The field studies included such physical items as the temperature, 

 the transparency, the color and the conductivity of the water, and 

 the rate at which the sun's energy is absorbed by the water in the 

 different types of lakes. The chemical items consisted of the deter- 

 mination of the hydrogen-ion concentration, dissolved oxygen, free 

 and fixed carbon dioxide, nitrate nitrogen, phosphorus, silica, chlo- 

 rine, and total residue. The biological phases of the work included 

 quantitative studies of the net and centrifuge plankton and of the 

 bottom fauna, and a general survey of the large aquatic plants; a 

 special collection of the molluskan fauna of the district was made. 

 Observations were made on 293 different lakes and lakelets during 

 the summer of 1929 ; of this number 157 had not been visited hitherto 

 and 136 had been visited in former years. Series of samples covering 

 the entire dej^th of the lake were obtained from 36 of these bodies 

 of water. Adding to these the series of samples taken in previous 

 years, such observations have now been made on every lake in the 

 northeastern district which has a known maximum depth of 20 

 meters or more ; many series have also been taken in shallower lakes, 

 such as those with maximum depths falling between 6 and 20 meters. 



L"p to the close of the 1929 season, 479 lakes and lakelets have been 

 visited during the progress of this investigation. This number in- 

 cludes all of the larger and more important lakes of the northeastern 

 district. Several hundred lakelets in this area have not been visited, 

 and only a few of the numerous bog ponds and lakelets have been 

 studied; the present plans do not include an extensive survey of 

 these smaller bodies of water in the near future. 



PACIFIC COAST AND ALASKA FISHERY INVESTIGATIONS 



The passing of the White law in 1924 greatly strengthened the 

 powers of the Department of Commerce, acting through the Bureau 

 of Fisheries, in making adequate regulations for the care and per- 

 petuation of the fishery resources of Alaska. Recognizing that the 

 regulations, to be most effective, must be based on a scientific knowl- 

 edge of the species exploited, the bureau has, from the first, devoted 

 efforts toward the study of the more important problems. Many of 

 the investigations have been concerned with purely local practical 

 problems but others of broader and more general application have 

 had an important place on the program. The practical value of the 



