Author: Ralph P. SILLIMANPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Fluctuations in Abundance of Columbia River Chinook Salmon 1928-54
Author: Harold A. GangmarkPublisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 30
Book Description
Fluctuations in Abundance of Columbia River Chinook Salmon, Oncorhynchus Tschawytscha, 1935-45
Author: Ralph P. SILLIMANFluctuations in Abundance of Columbia River Chinook Salmon (Oncorhynchus Tschawytscha)
Author: Ralph P. SillimanFactors Affecting the Abundance of Fall Chinook Salmon in the Columbia River
Author: Jack M. Van HyningPublisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 848
Book Description
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.
Spawning Areas and Abundance of Chinook Salmon (Oncorhynchus Tshawytscha) in the Columbia River Basin, Past and Present
Author: Leonard A. FultonIntraseasonal and Interseasonal Variations in Average Weight of Columbia River Chinook Salmon (Oncorhynchus Tschawytscha), 1939-1945
Author: Ralph Parks SillimanPublisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 54
Book Description
Spawning Areas and Abundance of Chinook Salmon (Oncorhynchus Tshawytscha) In the Columbia River Basin
Author: Leonard A. FultonPublisher: Forgotten Books
ISBN: 9781333761677
Category : Sports & Recreation
Languages : en
Pages : 56
Book Description
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.
Growth and Degree of Maturity of Chinook Salmon in the Ocean
Author: Willis Horton RichPublisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 96
Book Description
Spawning and Abundance of Fall Chinook Salmon (Oncorhynchus Tshawytscha) in the Hanford Reach of the Columbia River, 1948--1988
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 66
Book Description
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.
Managing the Columbia River
Author: National Research Council (U.S.). Committee on Water Resources Management, Instream Flows, and Salmon Survival in the Columbia River BasinPublisher: National Academy Press
ISBN:
Category : Business & Economics
Languages : en
Pages : 274
Book Description
Book News, Inc., Portland, OR (booknews.com).