BUREAU OF FISHERIES XIII 



chief features of the life history and movement with relation to 

 current, lio;ht, and other stimuli have been described, with recom- 

 mendations for control. 



FISH-CULTURAL INVESTIGATIONS 



These include studies on the salmon of the Columbia River, with 

 special reference to determining the most effective time, place, and 

 manner of planting the fry; studies on the embryology of the sal- 

 mon as a guide in the handling of the eggs; studies on nutrition, 

 breeding, and rearing of fresh-water trout; studies on the pond 

 culture of warm-water species of food and game fishes; and studies 

 on the cure and prevention of diseases in hatchery-reared fish. 



Special attention has been given to observing the effects of various 

 substitutes for fresh liver and heart on the growth of fry and finger- 

 lings. It has been found that the dried animal foods can not be 

 used alone successfully, but when combined with fresh liver or heart 

 many of them give good results. An essential part of the experi- 

 ments is the work on selective breeding, by means of which it is 

 hoped to produce a superior strain of trout showing rapid growth, 

 increased fecundity, and disease-resisting qualities. 



The results obtained during the summer of 1927 in using forage 

 fish as food for young large-mouthed black bass were particularly 

 encouraging. The yield of young bass under optimum conditions 

 exceeded 8,000 per acre, but it is believed that by the proper use of 

 forage fishes the output of fingerlings ( an be increased greatly. Both 

 the golden shiner and the black-head minnow have proved to be 

 excellent forage fishes, and goldfish also have shown desirable quali- 

 ties for this purpose. During 1928 the pond culture of smallmouth 

 black bass is being undertaken, and experiments on increasing plank- 

 ton production in ponds by means of various fertilizers have been 

 begun. During June, by the addition of shrimp bran to the ponds, 

 the total amount of plankton was increased four and one-half times 

 over that in untreated ponds, with the result that the bass fry showed 

 a material increase in length and weight in these ponds over those 

 grown under natural conditions. 



Investigations on the diseases of fish have been continued. One 

 particularly troublesome disease, for which treatment and cure have 

 been devised, is known as the " gill disease," which has broken out at 

 various times Avith great virulence and destructiveness. Further 

 studies were conducted on the "fin rot" disease, which also is very 

 destructive. The cause of the disease (a rod-shaped bacterium) has 

 been discovered, the symptoms described, and prevention and cure 

 devised. A brief investigation was undertaken at the request of the 

 American Railway Express Co. to determine the causes of the fre- 

 quent heavy losses of goldfish during shipment. Experiments also 

 were undertaken in the spring of 1928 on the feeding of goldfish 

 fingerlings to determine the more important factors that influence 

 their coloration. During the summer of 1927 studies on the life 

 history of the tapeworm parasite, which causes sterilization of female 

 bass, were undertaken at the Neosho (Mo.) hatchery, which is being 

 continued in 1928 with the hope of discovering means of control. 



