Effects of the Inter-age Crossbreeding of Coho Salmon (Oncorhynchus Kisutch) on Early Mortality and Growth PDF Download
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Author: Robert L. Hite
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 182
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Author: Robert L. Hite
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 182
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Author: Richard Allan Crone
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 158
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Behavior and survival in fresh water were studied for three brood years of coho salmon in Sashin Creek, Alaska, from October 1963, until September 1966. Investigations of spawning adults were conducted to determine numbers of spawners, distribution on the spawning grounds, effects on pink salmon, age composition, redd life, fecundities, and egg retention. Juvenile coho were studied to determine changes in population size, distribution in the stream, age composition of the population, food habits, and rates of mortality during fresh-water life. The number of coho spawners counted into Sashin Creek each year normally varied from 50 to 300. Weir counts and estimations of the number of spawners determined from observed spawning effort and redd life were not accurate methods of estimating the coho escapement into Sashin Creek. In 1965, a more accurate estimate was obtained by tagging a portion of the run and recording marked to unmarked ratios on the spawning grounds. I estimated that less than two percent of the viable pink salmon embryos were destroyed in 1965 by the spawning activities of coho salmon. Most coho spawners returned to Sashin Creek in 1965 and 1966 in their fourth year of life after having migrated to sea in their third year (designated 43). Smaller numbers of 32 and 54 individuals composed the remainder of the spawning population. The mean redd life of 56 females was 13 days. A small sample of coho from Sashin Creek examined for fecundity in 1966 gave a mean of 2,868 eggs per female. A weir or fyke net was fished in the spring to estimate emigration of juvenile coho. Coho smolts left Sashin Creek from April through July; peak emigration occurred in late May or early June. Coho fry left the stream in the spring and summer in widely varying numbers from year to year. I estimated from growth data, population estimates, and analysis of scale samples that most coho juveniles remained in Sashin Creek for two growing seasons before migrating to sea. Analysis of scales from juvenile coho indicated that some reabsorption of scales occurs during the winter. The possibility of reabsorption of circuli makes back-calculation of the length of younger age-groups of coho from scale measurements unreliable. Diptera were represented more often than any other order of insects in the stomachs of juvenile coho. Hemiptera were important as food items to juvenile coho in a tributary stream. The estimated survival from egg deposition to immediately prior to emergence varied between 17.5 and. 34.9 percent for the three brood years, and averaged 27. 8 percent. Early summer populations of fry were variable in size and dependent on the size of the egg deposition of the brood. Populations of fry declined rapidly during July and early August. Instantaneous mortality rates were much higher for this period than during any other time in the fresh-water life of coho salmon in Sashin Creek. Mortality dropped to a low level during the following winter period.
Author: Paul M. Iwanaga
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 56
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Author: Cary Lynn Feldmann
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 92
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Author: Mario Frank Solazzi
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 66
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Effects of inbreeding coho salmon (Oncorhynchus kisutch) on survival during early life history, growth, feed efficiency, and resistance to gas bubble disease were studied. No effect of inbreeding could be associated with either F=0.25 or F=0.125. Tetraploidy may help explain the absence of inbreeding depression at these levels.
Author: Terry R. Culp
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 166
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Author: James E. Morrow
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 58
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Report of a study to determine the degree to which crude oil and other hydrocarbons would affect fishes (coho salmon (Oncorhynchus kisutch) and sockeye salmon (Oncorhyunchus nerka)) and the mechanisms by which the effects were brought about. Such information becomes essential as the threat of oil pollution increases with the discovery and transport of oil from Alaskas North Slope and Prudhoe Bay.
Author: Harold W. Lorz
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 192
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Precocious male coho are of limited economic value and control of their numbers returning to the hatchery or the increased survival of full-sized adults would be beneficial. Factors influencing early sexual maturation and attempts to suppress this maturation of males through the incorporation of a hormone in the diet, treatment of parr with X-irradiation and control of the size at time of release by manipulation of the food were investigated. The investigation was carried out at the Fish Commission of Oregon's Big Creek Hatchery from June 1964 to January 1967 using the 1963 and 1964 broods of coho. A portion of the treated animals of the 1963 brood was retained through adult maturation in fresh water at Big Creek and a similar group was held in salt water at Bowmans Bay, Washington. Fish in one production pond received diethyistilbestrol incorporated into the Oregon Moist Pellet diet at 200 [mu]g/g from November 1964 through April 1965. Juvenile coho that received the various exposures of X-irradiation were taken to Corvallis for treatment and then returned to Big Creek. An experiment involving manipulation of diet to achieve two distinct sizes of smolts was initiated in April 1965 and carried through to March 1966, at which time the smolts were released. Juvenile coho salmon that received the hormone in their diet produced only half as many precocious males as the control when reared in fresh and saltwater ponds and only one quarter as many precocious males when released to the ocean. The adult survival for the two groups was equal in the ponds although only 30% of the hormone group was recovered at the hatchery as compared to the control. No long term effects on the viability of the gametes was noted but the mean length of fish in the hormone group was significantly smaller than that of the control fish. X-irradiation of parr did not inhibit early sexual maturation. No long term effects on the viability of gametes was noted. X-irradiation is not a practical tool for suppression of gonad development because juvenile coho have a low tolerance. Early sexual maturity is positively related to size of smolt at time of release. The release of larger smolts resulted in a 12-fold greater return of precocious male coho, and almost a twofold greater return of adults. From the results future suggestions for investigation are outlined. They include: further investigation of chemical suppression of the pituitary; various feeding regimes in an attempt to control growth; manipulation of hatchery procedures to produce smolts that would be migrants in their first year of life and combinations of the above.
Author: T. C. Yu
Publisher:
ISBN:
Category : Salmon
Languages : en
Pages : 9
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Author: Harold W. Lorz
Publisher:
ISBN:
Category : Coho salmon
Languages : en
Pages : 100
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