PROPAGATION^ AND DISTRIBUTION OF FOOD FISHES, 1921. 



59 



fertile, while the rate of fertility of the other lot was only 67. 

 This and further experiments along the same lines gave these results : 



It is unfortunate that more complete data on the.se experiments 

 are not available, and perhaps the data at hand can not be accepted 

 as conclusive. Nevertheless, the evidence seemed sufiiciently strong 

 to warrant the construction of two new ponds supplied entirely with 

 the McMahon water and the alteration of present lines to admit of 

 a further elimination of the Hearell water from the stock ponds. 

 During the coming year the brood stock of rainbow trout will be held 

 exclusively in ponds supplied with the McMahon water. The nature 

 of the apparent ill effects of the water from Hearell Spring on the 

 adult fish has never been ascertained, but an ovarian affection ap- 

 pears to prevail among the fish that have been retained in that water 

 for any considerable period. 



Another item of possible interest in trout culture at the Neosho 

 station was the occurrence of a disease among the fingerling trout, 

 both at the main station and at the Roaring River substation, re- 

 suhing in some loss. The trouble first api)eared as a discoloration 

 of the gills from cream to brown in color, sometimes one and some- 

 times both gills being affected, nds was followed by an apparent 

 disintegration of the tissues and finally by a peculiar sloughing off of 

 the gill. The trouble manifested itself only in the newly constructed 

 ponds or in ponds supplied with water from recently constructed 

 reservoirs. On being removed to surroundings entirely remote from 

 new concrete work the fish recovered rapidly, even in advanced cases 

 where the gill seemed to have been destroyed. After being treated 

 with a 1 to 1,000 solution of copper sulphate these affected ponds were 

 allowed to remain idle for several months, and no trouble in con- 

 nection with their use has since developed. 



The output of pond fishes also shows an improvement over the 

 recent past, the aggregate having been exceeded only in two previous 

 seasons. Further improvement in this line of effort involves some 

 interesting problems. The ovarian trouble of the rainbow trout may 

 be present among the pond fishes held in water from Hearell Spring, 

 and investigations looking toward the solution of this phase of the 

 subject are already under way. The station ponds devoted to the 

 |)ioduction of the warm-water species are well supplied with natural 

 food for their young, and were fingerling fish produced to the extent 

 of the natural food available the station's output would be materially 

 increased. The warm-water species propagated are largemouth and 

 .smallmouth black basses, rock bass, sunfish, crappie, and yellow 

 perch. Artificial nests were tried in connection with the spawning 

 of the largemouth black bass, with results that led the superintendent 

 to recommend their general use. The output of the station by species 

 is indicated in the tabular statement showing the production of fish 

 by stations on page 12. 



