PEOGEESS IN BIOLOGICAL, INQUIRIES, 19 31 497 



high to low oxygen concentrations, and the reverse, had no injurious 

 effects. In several instances fish used in these experiments were kept 

 under observation for several weeks, but in no case were there any 

 indications of injury to the gills. 



The experiments also showed that fish can tolerate a high carbon- 

 dioxide content, provided there is also a high concentration of dis- 

 solved oxygen. In some instances the CO2 content rose to over 50 

 parts per million without any apparent detrimental effect. 



These results have a very practical bearing, since they indicate 

 that it will be possible to ship fish for long distances in closed con- 

 tainers Avith an adequate supply of oxygen stored under pressure. 

 Further experiments in this direction are planned for the near future. 



Experiments on the effect of sudden changes in hydrogen-ion con- 

 centration (pH) on several species of fish show that they are able 

 to withstand rapid and extensive changes without any injurious 

 effects. Goldfish and green sunfish tolerated rapid changes from 

 pH 7.2 to 9.6 and from 8.1 to 6.0. Fingerling bass were apparently 

 unaffected by rapid changes from pH 6.1 to 9.5 and also by a simi- 

 lar change in the reverse direction. The experiments show that these 

 species of fish can tolerate the entire pH range of most unpolluted 

 lakes and rivers, and hence that hydrogen-ion concentration has very 

 little if any direct effect on the distribution of these fish in nature. 

 The results also indicate that no bad effects need be anticipated in 

 stocking natural waters when the fish are suddenly transferred to a 

 water with a quite different pH from that in which they were reared. 



UPPER MISSISSIPPI WILD LIFE AND FISH REFUGE 



Investigations in the sloughs of the Mississippi River bottoms in 

 the vicinity of Trempealeau, Wis., were continued during the sum- 

 mer of 1931 under the direction of E. W. Surber. 



As was the case at the Fairport station, three periods of unseason- 

 ably cold weather during the spawning season proved disastrous to 

 the eggs of the black bass. The number of fry which hatched was 

 so small that it was impossible to utilize most of the sloughs which 

 had been prepared for stocking with bass. Only about 40,000 fry 

 were obtained; and owing to unfavorable conditions in the sloughs 

 as a result of the abnormally hot, dry summer, only 5,330 fingerlings 

 were recovered in the fall. Conditions were more favorable for 

 bluegill sunfish, and Long Pond, which was stocked with 140 adults 

 of this species, produced 40,000 fine fingerlings. A much higher 

 production was obtained in Pickerel Slough, which yielded 320,000 

 fingerlings from 135 adults. 



Principally on account of their feeding habits, gizzard shad have 

 been frequently recommended as an ideal forage fish. It has, how- 

 ever, been impossible to get these fish to propagate in small bass 

 ponds, several attempts of this nature at Fairport having been at- 

 tended with failure. In the hope that the sloughs would afford more 

 favorable conditions, two ponds were stocked with large adult shad 

 early in the spring. These fish spawned successfully and large num- 

 bers of young were produced in both ponds. They grew very 

 rapidly, however, but it is questionable if they would make a satis- 

 factory food for young bass of the same season. On the other hand, 



