130 U-S. BUREAU OF FISHERIES 



the length of time required to digest minnows varied from 15 days 

 at a temperature of 4° C. to 12 hours at 28° C. At 10° C. 92 hours 

 were required for digestion while at 22° C. the food was completely 

 digested after 16 to 22 hours. The fish would not take food satis- 

 factorily at a temperature below 10° C, and it is apparent that bass 

 require very little food at these low temperatures. 



TISHOMINGO (OKLA.) STATION 



Investigations on certain phases of pond culture were carried on at 

 this station by O. Lloyd Meehean during the summer of 1932. The 

 ponds at Tishomingo are all new and are supplied with water from a 

 creek flowing through the station grounds. 



Experiments with Daphnia magna showed that this organism can 

 be reared successfully at the station if the temperature remains below 

 20° C. On the approach of hot weather the daphnia cultures deteri- 

 orated, and it was found impossible to keep them up during the sum- 

 mer. The daphnia were reared in concrete pools using drj sheep 

 manure and superphosphate as a fertilizer. Some preliminary exper- 

 iments on a small scale indicate that cottonseed meal will prove fully 

 as valuable as sheep manure or soybean meal for rearing daphnia. 



Routine collections of chemical and biological samples were made 

 in the station ponds to determine as far as possible the conditions in 

 each pond. The chemical data show that there is a large reservoir 

 of carbon dioxide in a half-bound state which can be utilized for the 

 growth of phytoplankton. The data also show the necessity for the 

 control of the rooted aquatics in order to keep the carbon dioxide 

 supply in an available condition. In most ponds the zoo-plankton 

 was not abundant and in several cases it was very poor. In practi- 

 cally all instances the plankton decreased as the summer progressed 

 and the amount of rooted vegetation increased. It is significant that 

 in ponds with small amounts of vegetation Cladocera were abundant 

 while in ponds with an abundant growth of rooted plants rotifers and 

 Cyclops were the dominant organisms. 



HACKETTSTOWN (N.J.) STATION 



A cooperative experiment in rearing smallmouth black bass was 

 carried on at the New Jersey State hatchery at Hackettstown by 

 A. M. McGavock. The primary purpose of the experiment was to 

 determine the most efficient and economical way to produce daphnia 

 for feeding young bass. In one case the daphnia were cultured in a 

 separate pond while in the other experiments the daphnia were grown 

 in the same ponds as the fish. The latter method was used in a pond 

 with an area 0.63 acre, which was fertihzed with approximately 8,000 

 pounds of fresh horse and cow manure in addition to about 2 inches 

 of trout excrement. As a result there was a very abundant growth 

 of plankton and bottom organisms in the pond during the summer. 

 The pond was stocked June 11 with bass fry at the rate of 25,000 per 

 acre. It was drained September 8 and yielded 8,178 fingerhngs aver- 

 aging 6.48 grams in weight, a survival of 51.8 percent. This is a 

 return of 12,990 fingerlings per acre. The total cost of labor and 

 manure was $174.30 or $13.40 per thousand fish. 



In another pond of approximately the same size daphnia were cul- 

 tured from trout excrement produced by fifteen thousand 8- to 10-inch 



