Lauren R. Donaldson

Development of Rainbow Trout Brood Stock by Selective Breeding

Abstract Management programs to maintain and increase the sports fishery require large numbers of strong, healthy, acclimatized fingerlings for restocking the lakes and streams. To produce the fingerling trout needed, stocks of fish are first developed and selected at fishery laboratories, then tested in the field. At the University of Washington over a period of 23 years of intensive selective breeding, rainbow trout (Salmo gairdnerii) stocks have shown increased growth rate, earlier maturity, increased tolerance to warm water temperatures, resistance to disease, and greatly increased egg production. The egg production has been most satisfactory, rising from an average of less than 1,000 eggs from 4-year-old spawners in 1932 to an average of 3,894 eggs for 2-year-old females, 5,029 for 3-year-old females, and 4,984 eggs for 4-year-old females in 1955.

Return of Silver Salmon, Oncorhynchus Kisutch (Walbaum) to Point of Release

Abstract Silver salmon, Oncorhynchus kisutch (Walbaum), of the 1950 brood year were reared at the Soos Creek Hatchery, State of Washington Department of Fisheries, until January 19, 1952. On that date, approximately 72,000 fingerlings were divided between the State of Washington salmon hatchery on Issaquah Creek and the ponds of the School of Fisheries, University of Washington. After two months of orientation, the two lots of fish were released to migrate to sea on March 18 and 19, 1952. The movement of the fish in the sea were followed by noting the return of the marked fish to the sport and commercial fisheries. Adult salmon returning during the winter of 1953–1954 were examined for marks. None of the marked fish returned to Soos Creek, their native stream. Those fish released at the School of Fisheries returned up the ladder to the rearing ponds and those released at Issaquah migrated to the head of the watershed, returning to the area of release.

Selective Breeding of Chinook Salmon

Abstract Selective breeding of plants and animals has been carried on for hundreds of years. Few attempts, however, have been made to breed salmon that have characteristics which would better fit the fish for the needs of modern salmon management. Experiments started in 1949 at the University of Washington to develop a selected stock of chinook salmon (Oncorhynchus tshawytscha) have shown progress in producing fish better adapted to the environment available to them. Selected stocks grow faster, are more resistant to high temperatures and disease, mature earlier, and have a higher survival rate than the non-selected stocks.

SEX RATIOS AND RETARDATION OF GONADAL DEVELOPMENT IN CHRONICALLY GAMMA- IRRADIATED CHINOOK SALMON SMOLTS.

Abstract The gonads of 4,405 premigratory smolts from eight year classes of chinook salmon, Oncorhynchus tshawytscha (Walbaum), were inspected to determine sex. Nearly half of the smolts of seven of the year classes had been irradiated for their first 80 days of life by exposure to the gamma rays of cobalt-60 at rates that increased almost exponentially from 0.5 R/day the first year to a maximum of 50 R/day the last year. Sex ratios were unaffected by 5 R/day or less, but at 10 or more R/day gonadal development was retarded.

University of Washington`s radioecological studies in the Marshall Islands, 1946-1977

Since 1946, personnel from the School of Fisheries, University of Washington (Applied Fisheries Laboratory, 1943-1958; Laboratory of Radiation Biology, 1958-1967; and Laboratory of Radiation Ecology, since 1967), have studied the effects of nuclear detonations and the ensuing radioactivity on the marine and terrestrial environments throughout the Central Pacific. A collection of reports and publications about these activities plus a collection of several thousand samples from these periods are kept at the School of Fisheries. General findings from the surveys show that (1) fission products were prevalent in organisms of the terrestrial environment whereas activation products were prevalent in marine organisms; (2) the best biological indicators of fallout radionuclides by environments were (a) terrestrial-coconuts, land crabs; (b) reef-algae, invertebrates; and (c) marine-plankton, fish. Studies of plutonium and americium in Bikini Atoll showed that during 1971-1977 the highest concentrations of 241Am, 2.85 Bq g(-1) (77 pCi g(-1)) and 239,240Pu, 4.44 Bq g(-1) (120 pCi g(-1)), in surface sediments were found in the northwest part of the lagoon. The concentrations in the bomb craters were substantially lower than these values. Concentrations of soluble and particulate plutonium and americium in surface and deep water samples showed distributions similar to the sediment samples. That is, the highest concentration of these radionuclides in the water column were at locations with highest sediment concentration. Continuous circulation of water in the lagoon and exchange of water with open ocean resulted in removal of 111 G Bq y(-1) (3 Ci y(-1)) 241Am and 222 G Bq y(-1) (6 Ci y(-1)) 239,240Pu into the North Equatorial Current. A summary of the surveys, findings, and the historical role of the Laboratory in radioecological studies of the Marshall Islands are presented.

Effects of Low-Level Chronic Irradiation of Chinook and Coho Salmon Eggs and Alevins

Abstract Chinook and coho salmon eggs were subjected to about 0.5 roentgen per day of the gamma radiation from cobalt-60 from shortly after fertilization until the alevins swam, resulting in a total dose to the chinooks of from 33 to 37 roentgens and to the cohos of 40 roentgens. Irradiated, and similarly treated but unirradiated controls, were compared for survival, growth, vertebral numbers and anomalies, opercular defects, and sex ratios. Significant differences were observed only in the more frequent occurrence of opercular defects among irradiated than among control coho salmon smolt. In some phases of growth the controls and in others the irradiated groups showed superiority without a discernible pattern. As late as the time of release of the smolt for their seaward migration, little if any difference appeared between experimental and control groups. Differences will be sought in the F1 generation from these fish.

Experimental Study of the Effect of Various Water Temperatures on the Growth, Food Utilization, and Mortality Rates of Fingerling Sockeye Salmon

Abstract Experiments were conducted with sockeye salmon fingerlings to determine the effect of various water temperatures on the growth, mortality, and food conversion of the fish. Maximum tolerance temperatures were determined, as were the optimum growth zones, as found in Skaha Lake, British Columbia, during the summer and fall months. The experimental data tend to confirm the field observations that young sockeye salmon have a preference for water temperatures similar to those found near the thermocline during the summer and fall months. The temperature of the surface layer of water in the lake was too high for optimum growth, survival, and efficient utilization of food.

Chronic Exposure of Chinook Salmon Eggs and Alevins to Gamma Irradiation: Effects on Their Return to Freshwater as Adults

Abstract Chinook salmon (Oncorhynchus tshawytscha) eggs and alevins were exposed to various levels of continuous gamma irradiation to determine the level at which the return of these individuals as adults would be affected. Large numbers of eggs (63,000 to 140,000) were used for each treatment, along with an equal number of controls. The dose rate ranged from 0.5 R/day in 1960 to 50 R/day in 1970; dose rate approximately doubled in each of the later years. After rearing for about 90 days, the control and irradiated groups were differentially marked and released for their migration to salt water. On their return 2 to 6 yr later, length, weight, and sex data were determined on each adult salmon. No significant change was noted in adult returns until irradiation levels of 10 R/day and above were used. At these levels (10 R/day, 20 R/day, and 17-50 R/day) analyses showed retardation in growth and increased mortality of the small salmon in fresh water, decreased numbers of adults returning to spawn, increased ...

Interracial Hybridization of Cutthroat Trout, Salmo Clarkii, and its Use in Fisheries Management

Abstract Two races of coastal cutthroat trout (Salmo clarkii) were hybridized and the resultant first generation hybrids were compared with the two parent races. In both laboratory and field studies the hybrids showed evidence of hybrid vigor. The catch of sports fishermen, during two seasons at Echo Lake, Washington, where both parent and hybrid trout were planted, was composed of three to six times as many fish of the hybrid stocks as of the parent races.

Effects of Chronic Exposure of Chinook Salmon Eggs and Alevins to Gamma Irradiation

Abstract Chinook salmon (Oncorhynchus tshawytscha) eggs and alevins were exposed continuously to low levels of gamma radiation from a 60Co source, from the instant of fertilization until the yolk sac was completely absorbed. The irradiated fish were compared with a similar stock that was not exposed to irradiation. The level of irradiation exposure was gradually increased from 0.5 roentgen/day for the 1960 brood year, to 1.3 roentgens/day in 1965, 2.8 roentgens/day in 1966, 5.0 roentgens/day in 1967 and to 10.0 roentgens/day, a total of 820 roentgens, for the 1968 brood year. At a level of 0.5 roentgen/day no damaging effects were found. The data for the higher levels of exposure will be evaluated as the adults return from the sea. Studies are carried on during the entire life span of the fish.