Download or read book Fluctuations in Abundance of Columbia River Chinook Salmon Oncorhynchus Tschawytscha 1935 45 written by Ralph P. SILLIMAN and published by . This book was released on 1950 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluctuations in Abundance of Columbia River Chinook Salmon Oncorhynchus Tschawytscha written by Ralph P. Silliman and published by . This book was released on 1950 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluctuations in Abundance of Columbia River Chinook Salmon 1928 54 written by Harold A. Gangmark and published by . This book was released on 1956 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Intraseasonal and Interseasonal Variations in Average Weight of Columbia River Chinook Salmon Oncorhynchus Tschawytscha 1939 1945 written by Ralph Parks Silliman and published by . This book was released on 1947 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluctuations in Abundance of Columbia River Chinook Salmon 1928 54 written by Harold A. Gangmark and published by . This book was released on 1956 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Factors Affecting the Abundance of Fall Chinook Salmon in the Columbia River written by Jack M. Van Hyning and published by . This book was released on 1968 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of the population ecology of Columbia River fall chinook salmon, Oncorhynchus tshawytscha (Walbaum), was made in an attempt to determine the cause of a serious decline in this run which occurred in the early 1950's. Fluctuations in abundance of major salmon runs the North Pacific were examined to detect any coastwide pattern. Only chinook salmon in Cook Inlet, Alaska, and chum salmon from Oregon to southwestern Alaska showed a similar trend. The following life history stages broken down into pre- and post-decline years were examined: (1) marine life including distribution and migration, growth and maturity, survival rate, oceanography, and commercial and sport fisheries; (2) upstream migration including river fisheries, gear selectivity, size and age composition of the run, escapement, and influence of dams, diseases, and water quality; (3) reproduction and incubation including spawning areas and spawning and incubation conditions; and (4) downstream migration which included predation, dams and reservoirs, diseases, flow, turbidity and temperature, and estuary life. Salient points of the analysis were: (1) a change in the maturity and survival pattern based on tagged and fin-clipped fish recovered before and after 1950; (2) a significant negative correlation between sea-water temperature during a year class' first year at sea and subsequent survival; (3) a large increase in the ocean fisheries coincident with the decline in the run; (4) catch-effort statistics of the ocean fishery show a near classic example of the effect of overexploitation; (5) estimates of the contribution of Columbia River chinook to the ocean fisheries based on tag recoveries could be underestimates rather than overestimates; (6) a significant inverse correlation between estimated ocean catch of Columbia River fall chinook and numbers entering the river; (7) size and age composition of the ocean and river catches decreased coincident with the decline in the run; (8) the gill-net fishery shows little size selectivity by age, size, or sex in the dominant group; (9) fluctuations in abundance of hatchery stocks are related to differences in survival between fingerling and adult; (10) hatchery, lower river, and upriver populations fluctuate in abundance in much the same pattern; (11) optimum escapement is between 90,000 and 100,000 adults, a value that was exceeded during most years; (12) a highly significant negative correlation between numbers of spawners and return per spawner; (13) most of the early dams had no direct effect on fall chinook and the decline in productivity occurred when river conditions were relatively stable; (14) temperatures at time of migration and spawning for fall chinook have not increased enough to be a serious mortality factor; (15) little relationship between flow, turbidity, and temperature at time of downstream migration and subsequent return was evident except that high temperatures and high flows (and turbidities) tended to produce poorer runs during certain time periods; and (16) predation and delay of smolts in reservoirs are largely unknown factors, but circumstantial evidence suggests that they were not important in regulating fall chinook numbers during the period of the study. Finally, variables that appeared to bear some relationship to fluctuations in abundance of fall chinook were submitted to multiple regression analysis. For the predecline period (1938-46 brood years), sea-water temperature and ocean troll fishing effort were significant variables (R2 = 0.74). For post decline years (1947-59 broods), troll had the most influence on total return with ocean temperature and escapement having lesser effects. For the combined years, troll intensity and ocean temperature were the significant variables (R2 = 0.572). Entering interaction of river flow at downstream migration with the other variables brought R2 to 0.754 which means that 75% of the variability in the returning run could be accounted for by these three factors. Return per spawner was so heavily influenced by numbers of spawners that the other factors assumed negligible importance. Equations were derived that predicted the returning run in close agreement with the actual run size. Substituting a low and constant troll fishing effort in the equation resulted in the predicted run maintaining the average predecline level. The increase in ocean fishing was the main contributor to the decline of the Columbia River fall chinook run as shown by correlation, by analogy, and by the process of elimination. To demonstrate why other chinook runs have not shown similar declines, it was shown that due to several unique features in Columbia River fall chinook life history they are exposed to much more ocean fishing than other populations. It was emphasized that these conclusions should not be extrapolated to the future or to other species or runs of salmon.
Download or read book Spawning Areas and Abundance of Chinook Salmon Oncorhynchus Tshawytscha in the Columbia River Basin Past and Present written by Leonard A. Fulton and published by . This book was released on 1968 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spawning Areas and Abundance of Chinook Salmon Oncorhynchus Tshawytscha In the Columbia River Basin written by Leonard A. Fulton and published by Forgotten Books. This book was released on 2018-02-21 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from Spawning Areas and Abundance of Chinook Salmon (Oncorhynchus Tshawytscha) In the Columbia River Basin: Past and Present Spawn in intermediate and large tribu taries and in middle reaches of the main stem. Spring-run chinook salmon Spawn in some lower Columbia River tributaries such as the Willamette, Cowlitz, and Kalama Rivers. They also are distributed in middle tributaries of the Columbia and Snake Rivers. (fall-run chinook salmon, discussed later in the report, share spawning grounds in some sections of the Cowlitz and Kalama Rivers.) These are not all of the areas in which such duplications occur but are cited as examples. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Download or read book Spawning and Abundance of Fall Chinook Salmon Oncorhynchus Tshawytscha in the Hanford Reach of the Columbia River 1948 1988 written by and published by . This book was released on 1990 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hanford Reach of the Columbia River provides the only major spawning habitat for the upriver bright (URB) race of fall chinook salmon in the mainstem Columbia River. Hanford Site biologists have conducted aerial surveys of spawning salmon in the Hanford Reach since 1948. This report summarizes data on fall chinook salmon spawning in the Hanford Reach and presents a discussion of factors that may affect population trends. Most data are limited to fisheries agency reports and other working documents. Fisheries management practices in the Columbia River system have changed rapidly over the last decade, particularly under requirements of the Pacific Northwest Power Planning and Conservation Act of 1980. New information has been generated and included in this report. 75 refs., 17 figs., 11 tabs.
Download or read book Changes in Size and Age at Maturity of Columbia River Upriver Bright Fall Chinook Salmon Oncorhynchus Tshawytscha written by Roy E. Beaty and published by . This book was released on 1992 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: The average size and age of chinook salmon (Oncorhynchus tshawytscha) caught in commercial fisheries along the Pacific Coast of North America have decreased substantially in this century. These declines might be caused in part by changes in size and age at maturity within the stocks contributing to those fisheries. Upriver Brights (Brights), a stock of fall chinook salmon in the Columbia River, are one of those stocks. The purposes of this study were to (1) determine if average size and age at maturity of Brights have declined, (2) gain a better understanding of the factors that may contribute to such declines, and (3) describe potential consequences of these changes. Data from in-river fisheries suggest that the average weight of mature Brights returning to the Columbia River has decreased approximately 2.7 kg since the 1910s, an average rate of about 0.1 lb·yr−1 (45 g·yr−1). Most of the potential biases in these data tend to make this estimate conservative. Insufficient data were available to describe changes in average age at maturity. There are many potential causes for the decline in average size of mature Brights, including factors that affect very early life stages. Other researchers have determined that size at maturity appears to be highly influenced by inheritance, gender, and growth rate. I describe how maternal size can influence -- through time of spawning, choice of spawning site, and egg size -- the viability of the young, which carry the dam's genes for size. The size-related ability to produce viable offspring may have been changed by modifications in the environment. Very little is known about how changes in the natural environment for spawning, incubation, and rearing may have contributed to a decline in average size at maturity. Artificial propagation and rearing, such as at Priest Rapids Hatchery, seems to produce adult Brights that are smaller, younger, and more likely to be male than their natural counterparts. The net result is that the average hatchery fish may have only about 0.80 of the reproductive potential of the average natural fish. Changes in growth conditions in the ocean probably did not contribute to the change in size, although the ocean fisheries of Southeast Alaska and British Columbia appear to select, in the genetic sense, against large size and old age in Brights. Since 1978, in-river commercial fisheries have caught larger Brights and a higher proportion of females than are found in the escapement of the Priest Rapids Hatchery component of the stock, but the fisheries impact the two sexes differently by taking the larger males and the smaller females. The effect on the natural component may differ because of their apparently larger average size. I found no evidence that larger fish or more females were caught when 8-in. minimum restrictions were in effect on gillnet mesh size relative to periods when mesh size was not restricted. Impounding the mainstem during the last 50+ yr may have removed obstacles to migration (e.g., Celilo Falls) that selected for large size in Brights, but that hypothesis could not be tested. The perserverance of larger and older phenotypes in the Bright stock suggests that countervailing selection -- perhaps during spawning, incubation, and/or early rearing -- may have resisted the effects of a century of size- and age-selective fisheries. That resistance, however, may reduce the productivity of the stock. Declines in average size and age at maturity can have undesireable consequences. Lower average size means less biomass landed and lower commercial value. Lower average fecundity and a diminished ability to reproduce in some environments are also expected. Loss of size and age classes may reduce the ability of the stock to adapt to environmental variations. These results are relevant to several management practices. A holistic approach to fishery management issues is necessary to avoid erroneous conclusions based on narrow perspectives. Measuring reproductive potential of the catch and escapement would be superior to the conventional practice of simply counting numbers of fish. Many aspects of artificial propagation can be improved, including broodstock aquisition, mating regimes, and rearing practices. Stock abundance is a major factor in determining the effect of many management practices on the stock. In general, fisheries managers must be mindful that they manage very complex natural systems.
Download or read book Objective Studies of Scales of Columbia River Chinook Salmon Oncorhynchus Tshawytscha walbaum written by Ted Swei-yen Koo and published by . This book was released on 1967 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Factors Influencing the Population Dynamics of Chinook Salmon Oncorhynchus Tshawytscha in Central California written by Robert Glenn Kope and published by . This book was released on 1987 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Estimation of the Troll Catch of Columbia River Chinook Salmon Oncorhynchus Tschawytscha written by Ralph Parks Silliman and published by . This book was released on 1948 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Factors Affecting the Abundance of 1977 79 Brood Wild Fall Chinook Salmon Oncorhynchus Tshawytscha in the Lewis River Washington written by Don McIsaac and published by . This book was released on 1990 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fishery Bulletin of the written by and published by . This book was released on 1947 with total page 834 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fishery Bulletin of the Fish and Wildlife Service written by and published by . This book was released on 1947 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Increased Water Temperatures on the Survival of Spring and Fall Juvenile Chinook Salmon Oncorhynchus Tschawytscha from the Lower Columbia River written by Theodore H. Blahm and published by . This book was released on 1970 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
