PROGRESS IN BIOLOGICAL INQUIRIES, 1930 605 



were available for these fish. One pond stocked with erappie and 

 blackhead minnows for fora<j;e produced 3,108 two-inch fingerlings, 

 Avhich was at the rate of 13,861 per acre. In another pond (D 2) 

 which was stocked with adult erappie and bluegill sunfishthe produc- 

 tion of erappie was at the rate of 13,988 per acre. In addition, this 

 pond produced 25,920 bluegills averaging about li/> inches in length. 

 This Was at the rate of 92,800 per acre. The total production of 

 erappie and bluegill sunfish was approximately 106,000 fingerlings 

 per acre. The results from this pond are in accord with those of 

 previous years in indicating that erappie and bluegills make a very 

 satisfactory combination, which works out to the mutual advantage 

 of both si:)ecies. 



Cooperative experiments. — In accordance wnth our program of 

 cooperative experiments at several hatcheries in different localities, 

 arrangements have been made to operate several ponds at the Tupelo 

 (Miss.) station on an experimental basis. During the season of 1931 

 these ponds will be stocked with bass and fertilized in the same way as 

 at Fairport. Conditions at the Tupelo station are very different 

 from those at Fairport, and these experiments will enable us to 

 determine if the methods developed at Fairport Avill be equally 

 successful at southern stations or wdiether they will require consid- 

 erable modification. 



LIMNOLOGICAL INVESTIGAIIONS 



Some preliminary observations by Doctor Wiebe during the sum- 

 mers of 1928 and 1929 indicated that the changes in the amount of 

 dissolved oxygen and alkalinity that occur in a pond within a 24- 

 hour period may be as large, if not larger, than the seasonal changes 

 when the observations are taken regularly at the same time each day. 

 For this reason it was decided to make a series of tests to determine 

 the extent in the diurnal variations in dissolved oxygen, alkalinity, 

 and in some instances ammonia nitrogen. These observations show 

 that very marked changes in the actual amount of dissolved oxygen 

 and in phenolphthalein alkalinity maj^ occur within 24 hours and that 

 the extent of these variations are determined by the abundance of 

 the alga?. It appears that the algae can utilize all of the CO2 present 

 as bicarbonate as Avell as some of the COo of the normal carbonate. 



A brief survey of the Clue River system in Nebraska was under- 

 taken by Dr. A. H. Wiebe and H. L. Canfield during July, 1930. 

 The purpose of the survey was to determine what species of game fish 

 might be successfully introduced into the streams that constitute the 

 river system. The streams were found to be adapted to both species 

 of black bass and to the bluegill sunfish, although none of these fish 

 are found in the Blue River or its tributaries at the present time. 

 The principal fish taken during the survey were the channel catfish, 

 white crapi)ie, crreen sunfish, carp, buffalo, and bullheads. 



UPPER MISSISSIPPI WILD LIFE AND FISH REFUGE 



The work in the Upper Mississippi Wild Life and Fish Refuge 

 was continued along the same lines as in 1929 under the immediate 

 direction of E. W. Surber. Detailed quantitative biological studies 

 of five sloughs in the bottoms of the Mississippi River which were 

 begun in the spring of 1929 were continued during the winter and 



