234 U. S. BUREAXT OF FISHERIES 



INVESTIGATIONS PERTAINING TO EISH-CULTURAL OPERATIONS 



The present well-organized program of research in this field, under 

 the direction of Dr. H. S. Davis, includes three major researches — 

 experimental trout culture, pond culture, and the pathology of hatch- 

 ery fish, including, respectively, the breeding, feeding, and rearing 

 of trout ; the culture and management of warm-water species of fish 

 in ponds ; and the conquest of fish diseases. 



In the latter part of September Dr. W. C. Kendall, ichthyologist 

 of the bureau, visited a semiprivate trout preserve in the Saddleback 

 Mountains in Maine, in order to supplement observations that have 

 been made every year since 1922, inclusive. It was interesting to 

 find that since 1926, when "fresh-water shrimp " (mostly Ganimarus 

 fasciatus) were introduced, great improvement had occurred in part 

 of one small pond. In 1926 the largest trout observed were not 

 over 7 inches in length, white-meated, and in poor condition gen- 

 erally, all of Avhich was attributed to lack of suitable food. In 1927 

 some trout nearly half a pound in weight were observed, and all were 

 plump and red-meated. 



At the request of a sportmen's association of Bath, Me., a pond 

 below Phippsburg, on Cape Small Point, was examined early in the 

 summer to ascertain whether or not it was suited to the introduction 

 of brook trout, and, except for the limited extent of the spawning 

 areas, it was pronounced capable of supporting a small number of 

 trout. In June "fresh-water shrimp" (chiefly Hyalella knicker- 

 hockeri^ but some Ganvnimms fasciatus) and samples of water were 

 collected from a stream in North Windham for the Board of Fish- 

 eries and Game of Connecticut. In July the Craig Brook station^ 

 was inspected to determine the advisability of constructing rearing 

 ponds for young salmon and trout, and in November the old canal 

 at Grand Lake Stream station was inspected with a view to utilizing 

 it as a retaining inclosure for young landlocked salmon. 



EXPERIMENTAL TEOUT CULTURE 



During the summer of 1927 experiments in feeding fingerling and 

 yearling trout were continued at the Holden (Vt.) experiment hatch- 

 ery by R. F. Lord under the supervision of Doctor Davis. In 

 previous years the experimental work to discover fish foods that 

 produce rapid growth but low mortality has been handicapped 

 seriously by a gill disease which killed many fish and obscured the 

 effect of the various foods. Methods were developed to control this 

 disease, so that this season the results will show the relative value 

 of the different foods uncomplicated by any effects of gill disease. 



Each ration was fed to both brook and rainbow fingerlings for a 

 period of 127 days, the fish being held in standard hatchery troughs 

 in lots of 1,000. Beef liver, beef heart, and sheep liver were selected 

 as food for the control lot, as these meats are considered standard 

 diets for fish in hatchery practice. The other lots were fed these 

 meats in combination with clam meal, soy-bean meal, or Mexican 

 beans, in the proportion of three parts of fresh meat to one part of 

 the substitute. The soy-bean meal and Mexican beans Avere cooked 

 to the consistency of thick mush and the clam meal was mixed with 



