Age Composition and Mark and No-tag Rates of the Escapement of Upriver Bright Stock Fall Chinook Salmon, 1986 PDF Download
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Author: Ron Roler
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages :
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Author: Ron Roler
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages :
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Book Description
Author: Ron Roler
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages :
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Author: Roy E. Beaty
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 540
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Book Description
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: Jim Waldvogel
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 48
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Age analysis for 22 years (1980 excluded) showed that the overall percentages for female spawners was 53% (4-year olds), 38% (3-year olds), and 9% (5-year olds). The age composition of male spawners showed a high degree of variability throughout the study. Male chinook of age 2, 3 and 4 were dominant annually, but 5- and 6- year old fish were present in most spawning seasons. All chinook carcasses from which scales were collected were also measured for length (over 120 samples in 22 years). Decreases in mean length were documented for all age classes for each of the El Nino episodes that occurred during the study (1982-1984; 1992-1993; 1997-1998). The decreases in mean length appeared to carry forward for each cohort's age class. The total number of chinook redds was tabulated by counting "fresh" redds during weekly spawning surveys. The mean number of redds was 117 for the 23-year period with a mean of 0.9 redds per adult salmon or 1.8 redds per female.
Author: Cindy LeFleur
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 6
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Author:
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Category :
Languages : en
Pages : 126
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The chinook salmon of the Campbell/Quinsam river system were selected as one of the indicator stocks for assessing the response of Pacific chinook salmon stocks to a new harvest management regime, begun in 1984, to build stocks to historical levels. This report presents the results from 1986-88 of intense escapement monitoring and sampling of chinook salmon, calculated using the adjusted Petersen method by tagging carcasses to produce separate estimates for sexes and rivers and summing these to form a total estimate for the in-river escapement of chinook. The total recovery of chinook salmon at the Quinsam Hatchery was then added to the in-river estimates to produce a final escapement figure for the entire system. Potential biases in the Petersen method, the carcass and live tagging approaches, and method of stratification are discussed. The results give population estimates and composition (age, length, and sex) and results of coded wire tagging studies.
Author: Cornelius M. Sullivan
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 138
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Author: Brian W. Elliott
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 0
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An ongoing coded wire tag project, used as part of a stock assessment program for Chilkat River Chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch, will be conducted during fall 2022 and spring 2023 to provide estimates of smolt abundance and marine harvest for Chinook and coho salmon. This project uses modified Peterson 2-event mark–recapture methods to estimate smolt abundance, and port sampling of coded wire tags in mixed stock commercial and sport fisheries to estimate marine harvest for both species. Juvenile salmon will be measured for length and weight, marked with adipose fin clips, and tagged with coded wire tags in fall 2022 (juvenile Chinook salmon) and spring 2023 (Chinook and coho salmon smolt) as event 1 of the mark–recapture study. During event 2, adult Chinook salmon will be sampled for missing adipose fins, coded wire tags, age, sex, and length in Chilkat River fishwheels and drift gillnets, which are operated in the lower Chilkat River as part of a separate adult mark–recapture project. Adult Chinook salmon will be also sampled for missing adipose fins, coded wire tags, and age, sex, and length during Chilkat River drainage spawning grounds surveys to complete event 2 sampling. Coho salmon will also be sampled as adults during event 2 in the lower Chilkat River fishwheels. Age composition of Chinook salmon adults will be estimated by scale ageing techniques; age composition of coho salmon smolt and adults will also be estimated. The Alaska Department of Fish and Game uses these data to make local and regional management decisions. Chilkat River Chinook salmon is a Pacific Salmon Commission exploitation rate and escapement indicator stock and has recently been added to the base model of abundance indicator stocks for the Chinook Technical Committee, which influences coastwide management.
Author: Julie Hooff
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 24
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Author: Brian W. Elliott
Publisher:
ISBN:
Category : Chinook salmon
Languages : en
Pages : 0
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Chilkat River large (age-1.3 and older) Chinook salmon Oncorhynchus tshawytscha inriver abundance and age and sex composition will be estimated using a 2-event mark–recapture experiment in 2022. Event 1 marking is conducted in the lower Chilkat River, and event 2 recapture is conducted in principal spawning areas within the Chilkat River drainage. Data produced from this project includes estimated spawning abundance and age, sex and length compositions of the large Chinook salmon run, and when possible, estimated spawning abundance and sex and length composition of the age-1.2 Chinook salmon run in the Chilkat River drainage. The Chilkat River stock of Chinook salmon is a Pacific Salmon Commission Chinook Technical Committee exploitation rate and escapement indicator stock, and contributes toward the coastwide Chinook model used by the Pacific Salmon Commission to monitor coastwide abundance. Mark–recapture experiments of adult Chinook salmon inriver abundance have been conducted in the Chilkat River drainage since 1991 and resulting escapement estimates have had an average coefficient of variation of 16%, which contributes toward precise stock assessment production estimates for the Chilkat River Chinook stock. As part of ongoing Chilkat River Chinook salmon coded wire tag studies, all Chinook salmon encountered in the mark–recapture experiment of adult Chinook salmon inriver abundance will be examined for missing adipose fins, an indication that fish may be tagged with a coded wire tag, information that leads to estimates of juvenile production and marine harvest. These data when used in conjunction with inriver abundance allows full production estimates for the Chilkat stock.
