The Effect of River Flow on Abundance of Pre-smolt Fall Chinook Salmon in the North Lewis River Below Merwin Dam, 1978-80 and 1983-85 PDF Download
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Author: Guy Norman
Publisher:
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Category : Chinook salmon
Languages : en
Pages :
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Author: Guy Norman
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Aquatic sciences
Languages : en
Pages : 736
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Author: Jack M. Van Hyning
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 848
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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.
Author: Don McIsaac
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 348
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Category :
Languages : en
Pages :
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The development of the Snake River hydroelectric system has affected fall Chinook salmon smolts by shifting their migration timing to a period (mid- to late-summer) when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River Chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations (e.g., summer flow augmentation) to improve water temperature and flow conditions during the juvenile Chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall Chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated. This report describes research conducted by the Pacific Northwest National Laboratory (PNNL) that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall Chinook salmon spawning areas. This was a pilot-scale study to evaluate these relationships under existing operations of Hells Canyon Dam (i.e., without any prescribed manipulations of river discharge) during the 2002-2003 water year.
Author: Don McIsaac
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 16
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 164
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The development of the Snake River hydroelectric system has affected fall Chinook salmon smolts by shifting their migration timing to a period (mid- to late-summer) when downstream reservoir conditions are unfavorable for survival. Subsequent to the Snake River Chinook salmon fall-run Evolutionary Significant Unit being listed as Threatened under the Endangered Species Act, recovery planning has included changes in hydrosystem operations (e.g., summer flow augmentation) to improve water temperature and flow conditions during the juvenile Chinook salmon summer migration period. In light of the limited water supplies from the Dworshak reservoir for summer flow augmentation, and the associated uncertainties regarding benefits to migrating fall Chinook salmon smolts, additional approaches for improved smolt survival need to be evaluated. This report describes research conducted by the Pacific Northwest National Laboratory (PNNL) that evaluated relationships among river discharge, hyporheic zone characteristics, and egg pocket water temperature in Snake River fall Chinook salmon spawning areas. This was a pilot-scale study to evaluate these relationships under existing operations of Hells Canyon Dam (i.e., without any prescribed manipulations of river discharge) during the 2002-2003 water year. The project was initiated in the context of examining the potential for improving juvenile Snake River fall Chinook salmon survival by modifying the discharge operations of Hells Canyon Dam. The potential for improved survival would be gained by increasing the rate at which early life history events proceed (i.e., incubation and emergence), thereby allowing smolts to migrate through downstream reservoirs during early- to mid-summer when river conditions are more favorable for survival. PNNL implemented this research project at index sites throughout 160 km of the Hells Canyon Reach (HCR) of the Snake River. The HCR extends from Hells Canyon Dam (river kilometer [rkm] 399) downstream to the upper end of Lower Granite Reservoir near rkm 240. We randomly selected 14 fall Chinook salmon spawning locations as study sites, which represents 25% of the most used spawning areas throughout the HCR. Interactions between river water and pore water within the riverbed (i.e., hyporheic zone) at each site were quantified through the use of self-contained temperature and water level data loggers suspended inside of piezometers. Surrounding the piezometer cluster at each site were 3 artificial egg pockets. In mid-November 2002, early-eyed stage fall Chinook salmon eggs were placed inside of perforated polyvinyl chloride (PVC) tubes, along with a temperature data logger, and buried within the egg pockets. Fall Chinook salmon eggs were also incubated in the laboratory for the purpose of developing growth curves that could be used as indicators of emergence timing. The effects of discharge on vertical hydrologic exchange between the river and riverbed were inferred from measured temperature gradients between the river and riverbed, and the application of a numerical model. The hydrologic regime during the 2002-2003 sampling period exhibited one of the lowest, most stable daily discharge patterns of any of the previous 12 water years. The vertical hydraulic gradients (VHG) between the river and the riverbed suggested the potential for predominantly small magnitude vertical exchange. The VHG also showed little relationship to changes in river discharge at most sites. Despite the relatively small vertical hydraulic gradients at most sites, results from the numerical modeling of riverbed pore water velocity and hyporheic zone temperatures suggested that there was significant vertical hydrologic exchange during all time periods. The combined results of temperature monitoring and numerical modeling indicate that only 2 of 14 sites were significantly affected by short-term (hourly to daily) large magnitude changes in discharge. Although the two sites exhibited acute flux reversals between river water and hyporheic water resulting from short-term large magnitude changes in discharge, these flux reversals had minimal effect on emergence timing estimates. Indeed, the emergence timing estimates at all sites were largely unaffected by the changes in river stage resulting from hydropower operations at Hells Canyon Dam. Our results indicate that the range of emergence timing estimates due to differences among the eggs from different females can be as large as or larger than the emergence timing estimates due to site differences (i.e., bed temperatures among sites). We conclude that during the 2002-2003 fall Chinook salmon incubation period, hydropower operations of Hells Canyon Dam had an insignificant effect on fry emergence timing at the study sites.
Author:
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Category :
Languages : en
Pages : 140
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This report summarizes results of research activities conducted in 1999 and years previous. In an effort to provide this information to a wider audience, the individual chapters in this report have been submitted as manuscripts to peer-reviewed journals. These chapters communicate significant findings that will aid in the management and recovery of fall chinook salmon in the Columbia River Basin. Abundance and timing of seaward migration of Snake River fall chinook salmon was indexed using passage data collected at Lower Granite Dam for five years. We used genetic analyses to determine the lineage of fish recaptured at Lower Granite Dam that had been previously PIT tagged. We then used discriminant analysis to determine run membership of PIT-tagged smolts that were not recaptured to enable us to calculate annual run composition and to compared early life history attributes of wild subyearling fall and spring chinook salmon. Because spring chinook salmon made up from 15.1 to 44.4% of the tagged subyearling smolts that were detected passing Lower Granite Dam, subyearling passage data at Lower Granite Dam can only be used to index fall chinook salmon smolt abundance and passage timing if genetic samples are taken to identify run membership of smolts. Otherwise, fall chinook salmon smolt abundance would be overestimated and timing of fall chinook salmon smolt passage would appear to be earlier and more protracted than is the case.
Author: Kale T. Bentley
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 73
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Author: Lloyd A. Phinney
Publisher:
ISBN:
Category : Fishes
Languages : en
Pages : 23
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