I PROGEESS IN BIOLOGICAL INQUIRIES, 1929 1103 



Dr. H. S. Davis, in charge aquicultural investigations. The work at 

 this hatchery, which is under the immediate supervision of R. F. 

 Lord, is primarily concerned with brook trout, and a large stock of 

 these fish of various ages is maintained for experimental purposes. 

 Small numbers of rainbow, steelhead, and black-spotted trout are 

 also kept at this station, and during the past summer the stock 

 was increased by a shipment of grayling eggs from Montana. In 

 order to accommodate such a large and varied assortment of fish a 

 large number of small ponds and raceways are required, and these 

 are being increased as rapidly as funds will permit. 



During the past season the brook trout spawned at this station 

 produced approximately 950,000 eggs. These eggs were taken from 

 several strains of fish originally obtained from widely separated 

 sources so that trout of quite different ancestry will be available for 

 breeding purposes. In addition to the brook-trout eggs, several 

 thousand rainbow eggs were also taken. It may be of interest to 

 note that there are two strains of rainbow trout at the station, one 

 spawning in the spring and the other in the fall. 



FEEDING EXPERIMENTS 



The feeding experiments carried on during the summer of 1929 

 were planned along the same general lines as in the previous year. 

 Fingerling and yearling brook trout were utilized in these experi- 

 ments, the fingerlings being kept in hatchery troughs, while the year- 

 lings were held in outdoor raceways. Twenty-one lots of fingerlings, 

 containing 1,500 fish each, w^ere kept on experimental diets which 

 were designed primarily to furnish additional data on the feasibility 

 of utilizing dry meals in rations of fish of this age. 



Dry feeds for fingerling hrooh trout. — As a result of the experi- 

 ments during the last two j^ears in feeding substitutes for fresh meats 

 to fingerling trout, it is believed that it is entirely practicable to use 

 certain dry products in combination with fresh meat at a consider- 

 able saving over the cost of a straight fresh-meat diet. These experi- 

 ments have shown that fingerlings fed a mixture of fresh meat and 

 certain dry products do fully as well as fish on a diet of fresh meat 

 alone, and in some instances even better. It is not believed however, 

 that in most instances it will be found practicable to feed these dry 

 products to fish under 2 inches in length. 



Only a few drj'- products have been found to give satisfactory 

 results with small fingerlings. Clam meal has made by far the best 

 showing of any of the dry products tested, but unfortunately the 

 supply of this meal is very limited. Dry buttermilk and dry skim 

 milk have also been found to produce good results and, everything 

 considered, are probably the best dry products for feeding small 

 fingerlings which are available in quantity. As high as 25 per cent 

 of these meals when mixed with beef liver has been found to yield 

 results comparable to those obtained with liver alone. 



After the fingerlings reach a length of 4 to 5 inches a wider range 

 of dry meals is available, such as shrimp meal and vacuum-dried 

 fish meals. 



Dry feeds for yearling hrook trout. — The experiments with year- 

 ling brook trout during the summer of 1929 were conducted on a 

 larger scale than ever before, 24 lots of fish being placed on experi- 



