An Investigation Into the Factors Influencing Escapement Estimation for Chinook Salmon (Oncorhynchus Tshawytscha) on the Lower Shuswap River, British Columbia [microform] PDF Download
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![An Investigation Into the Factors Influencing Escapement Estimation for Chinook Salmon (Oncorhynchus Tshawytscha) on the Lower Shuswap River, British Columbia [microform] PDF](https://books.google.com/books/content/images/frontcover/5NQBywEACAAJ?fife=w150-h200)
Author: Nicole Dorothy Trouton
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494036549
Category : Chinook salmon
Languages : en
Pages : 214
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Book Description
The area-under-the-curve (AUC), method based on helicopter visual enumeration, is a commonly used technique to estimate escapement of chinook salmon (Oncorhynchus tshawytscha) for the Fraser River and its tributaries. Two key factors associated with this method are survey life and observer efficiency. The survey life currently assumed by Fisheries and Oceans Canada (DFO) for Thompson Basin streams is seven days and for most counting flights the assumed observer efficiency is 100%. Telemetry and tower observations were used to estimate annual (2000-2002) survey lives for male (telemetry) and female (telemetry and tower observation) chinook salmon in the Lower Shuswap River. Mark-recapture based survey lives were directly estimated by dividing the mark-recapture escapement estimate by the AUC estimate of total spawner days. Observer efficiency was estimated by comparing observer counts from helicopters to counts from photographs. Various combinations of total fish counts, observer efficiencies, and survey lives were used in AUC escapement estimates, and compared to mark-recapture and peak count estimates. Survey lives varied annually. Many of the estimated mean survey lives were significantly less than seven days; mark-recapture based survey lives were generally less than those estimated from telemetry and observations from towers; and mean survey lives for males were higher than for females. The mean observer efficiency of helicopter enumeration was 97% (95% CI is * 6%), this is not significantly different than the 100% assumed by DFO.
![An Investigation Into the Factors Influencing Escapement Estimation for Chinook Salmon (Oncorhynchus Tshawytscha) on the Lower Shuswap River, British Columbia [microform] PDF](https://books.google.com/books/content/images/frontcover/5NQBywEACAAJ?fife=w80-h100)
Author: Nicole Dorothy Trouton
Publisher: Library and Archives Canada = Bibliothèque et Archives Canada
ISBN: 9780494036549
Category : Chinook salmon
Languages : en
Pages : 214
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Book Description
The area-under-the-curve (AUC), method based on helicopter visual enumeration, is a commonly used technique to estimate escapement of chinook salmon (Oncorhynchus tshawytscha) for the Fraser River and its tributaries. Two key factors associated with this method are survey life and observer efficiency. The survey life currently assumed by Fisheries and Oceans Canada (DFO) for Thompson Basin streams is seven days and for most counting flights the assumed observer efficiency is 100%. Telemetry and tower observations were used to estimate annual (2000-2002) survey lives for male (telemetry) and female (telemetry and tower observation) chinook salmon in the Lower Shuswap River. Mark-recapture based survey lives were directly estimated by dividing the mark-recapture escapement estimate by the AUC estimate of total spawner days. Observer efficiency was estimated by comparing observer counts from helicopters to counts from photographs. Various combinations of total fish counts, observer efficiencies, and survey lives were used in AUC escapement estimates, and compared to mark-recapture and peak count estimates. Survey lives varied annually. Many of the estimated mean survey lives were significantly less than seven days; mark-recapture based survey lives were generally less than those estimated from telemetry and observations from towers; and mean survey lives for males were higher than for females. The mean observer efficiency of helicopter enumeration was 97% (95% CI is * 6%), this is not significantly different than the 100% assumed by DFO.
Author: Charles O. Junge
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 40
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Author: Stephen A. Gough
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 136
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Author: Roy E. Beaty
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 540
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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.
Author: Ian Geoffrey Brosnan
Publisher:
ISBN:
Category :
Languages : en
Pages : 366
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From 2008 to 2011, migrating acoustic-tagged juvenile yearling Chinook salmon smolts (Oncorhynchus tshawytscha) were detected on receivers deployed across the Columbia River and continental shelf at Cascade Head (Oregon), Willapa Bay (Washington), and Vancouver Island (British Columbia). The telemetry data were used to estimate survival and record migration parameters. These were evaluated against oceanographic and freshwater hydrologic variables in statistical and individual-based models. Plume survival was found to be variable, but daily survival rates were more constant and survival was effectively modeled as exponential decay. Correlates of early marine survival that do not have direct effects may act on plume survival by controlling the period of exposure to plume predation. In 2011, half of smolts released were exposed to total dissolved gas levels (TDG) above 120%, the water quality limit for TDG below Columbia River dams. This exposure appears to have negatively affected daily survival rates in the lower river and plume, and has important implications for a proposal to increase the TDG limit to 125% to support spring fish passage. Finally, consistent with the critical size, critical period hypothesis of salmon production, it appears that smolts select habitat to maximize their growth as they migrate north through the plume, rather than selectively using local currents to speed their passage. These findings shed new light on perennial questions in salmon early marine ecology. They lay the groundwork for future research aimed at understanding the effects of changing oceanography and freshwater hydrology on salmon migration and survival.
Author: Michael R. Link
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 0
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Since 1994, a mark-recapture experiment has been used to estimate the annual system-wide chinook salmon escapement to the Nass River, British Columbia. This report describes and presents results from the 1997 experiment, which was designed to test some basic assumptions that heretofore had not been rigorously examined. The objectives of the study were to: determine if the fishwheels used to capture the salmon were size- and/or stock-selective, and if so, examine the implications of ignoring fishwheel selectivity when estimating escapement; estimate the abundance of chinook spawning in the Nass watershed in 1997; and recommend a cost-efficient, long-term study design to accurately estimate the annual, system-wide escapement of chinook to the Nass River. Results are presented and discussed with regard to catches, catch per unit effort, tagging, tag recovery and loss, spawning ground surveys, size selectivity, recoveries among tributaries of the Nass River, and factors affecting escapement estimates. Recommendations are made for the 1998 study.
Author: Jan L. Weller
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 35
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This report estimates the abundance of medium and large chinook salmon, Oncorhynchus tshawytscha, that returned to spawn in the Unuk River in 2005, using a two-event mark-recapture experiment.
Author: Tracy R. Hansen
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 0
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Objectives of this study are to estimate the spawning escapement and run timing of Chinook salmon Oncorhynchus tshawytscha in an index area of the Gulkana River using counting tower methodology. In addition, sockeye salmon O. nerka escapement at the tower site will be estimated during the period of tower operation. The number of Chinook salmon and sockeye salmon passing the tower site will be estimated by visually counting fish as they pass 2 counting towers located approximately 2.5 km upstream of the confluence of the West Fork. Ten-minute visual counts will be conducted for each river channel every hour, 24 hours per day, 7 days per week. The abundance estimates will be stratified by day. Because counts are planned for all hours, daily estimates of abundance will be a single-stage direct expansion from the 10 min counting periods. The count schedule will start prior to the beginning of the Chinook salmon run, approximately 3 June, and continue until after 10 August when the run is complete. Tower operations may be extended to a later date to enumerate more of the sockeye salmon run if funding is provided by Prince William Sound Aquaculture Corporation.
Author: Jan L. Weller
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 40
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Book Description
This report estimates the abundance of medium and large chinook salmon Oncorhynchus tshawytscha that returned to spawn in the Unuk River in 2004, using a two-event mark-recapture experiment.
![Estimated Abundance of Chinook Salmon Returning to the Nass River, B.C., 1997 [microform] PDF](https://books.google.com/books/content/images/frontcover/wF10NAEACAAJ?fife=w80-h100)
Author: Canada. Department of Fisheries and Oceans. Science
Publisher: Prince Rupert, B.C.: Fisheries and Oceans Canada
ISBN:
Category :
Languages : en
Pages : 64
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