1106 U. S. BUEEAU OF FISHERIES 



growth on this diet, and the losses were comparatively light. The 

 grayling fingerlings continued to thrive throughout the summer, and 

 on October 1 many had reached a length of 2 to 2.5 inches. With 

 the arrival of cold weather the growth rate was reduced, but the fish 

 remained healthy; and there is every reason to believe that they will 

 survive the winter in good condition. 



It is planned to use part of these grayling to stock a suitable stream 

 in the vicinity of Pittsford, Avhile the remainder will be reared to 

 maturity at the hatchery. 



DISEASES OF TROUT 



Investigations on the parasites and diseases of trout were contin- 

 ued, special attention being paid to the gill disease which has been 

 found to be one of the most serious diseases with which the trout 

 culturist has to deal. It is a very widely distributed disease, having' 

 been found in trout and salmon from the New England States to the 

 Pacific coast. Undoubtedly the disease has been prevalent at trout 

 hatcheries for many years, but its true nature has only recently been 

 recognized. Formerly losses which were evidently due to this dis- 

 ease were ascribed to the water supply and other obscure agencies. 

 Fortunately, as noted in previous reports, the disease is easily con- 

 trolled if the appropriate measures are taken on the first appearance 

 of the infection. 



An epidemic of " popeye " which caused serious losses among 

 fingerling black-spotted trout and sockeye salmon at the Birdsview 

 (Wash.) station was found to be associated with infection of the 

 kidney by a myxosporidian parasite. This parasite, which is ap- 

 parenth' an undescribed species of Myxidium, occurs in the lumen 

 of the kidney tubules causing; pathological changes in the epithelial 

 lining. The " popeye " condition is due to the accumulation of serous 

 fluid in the abdominal cavity and other parts of the body and it is 

 probable that this is the result of the kidney infection. 



INVESTIGATIONS IN POND FISH CULTITRE 



The investigations in pond fish culture at the Fairport (Iowa) 

 station, under the immediate direction of Dr. A. H. Wiebe, were 

 continued along the same general lines as in previous years under 

 the general supervision of Dr. H. S. Davis. The object of these 

 experiments is to devise better and more efficient methods of propa- 

 gating and rearing the so-called warm-water game fishes, including 

 the large and smallmouth black bass, the white and black crappie, 

 and the bluegill sunfish. 



Experiments icith golden shiner amd hlcuchhead minnow as forage. — 

 Since previous experiments had shown the advisability of utilizing 

 forage minnows in i^aring both large and smallmouth bass, the in- 

 vestigations during the past year were designed primarily to fur- 

 nish further information regarding this phase of bass culture. 

 Experiments with the golden shiner and blackhead minnow have 

 shown that as a forage fish for bass the shiner is superior to the 

 blackhead. There still remained, however, a possibility that both 

 species of minnows in a pond would prove superior to either one 

 alone, since they differ widely in their feeding and breeding habits. 



