Upstream Salmon and Society in the Pacific Northwest (1996) / Chapter Skim
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11 Salmon-Fishery Management Concepts
11 Salmon-Fishery Management Concepts
Pages 275-301
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From page 275... ...
reported that "regulations for controlling harvest were inadequate, but insufficient information existed on which to construct better techniques; hatchery practices were fairly advanced but of dubious value; inroads on salmon production as a consequence of the development of other resources were begin 275
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From page 276... ...
Surplus in the case of salmon means that a given number of spawners in an adult generation produces, on average, more progeny than needed to replace the parents and overcome all natural mortality sources from the time fertilized eggs are deposited in the gravel of natal streams, through juvenile and immature life phases, to adulthood. The number of surplus animals varies with the size of the population and the natural mortality rate.
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From page 277... ...
However, if the function value Rat expected for a particular So exceeds the replacement value, then a surplus production (R~ - Sit could be caught and the population maintained in equilibrium at the same future S and R numbers. Salmon populations can maintain themselves at several levels of abundance, and different salmon populations have different stock-recruitment curves.
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From page 278... ...
Furthermore, the scatter plot of alpha versus beta values (SIR param
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From page 279... ...
adult spawners and juvenile downstream migrants (age 1 + smelts) ; and C, migrants and adult returns.
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From page 280... ...
In salmon populations in which recruitment and spawning stock sizes have been monitored, annual variation in the ratio of returns to spawners can vary by a factor of 10. Recently the marine survival rate of chinook salmon released from Robertson Creek Hatchery (on the west coast of Vancouver Island, B.C.)
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From page 281... ...
The most common concern about managing for MSY in salmon fisheries is that stock-recruitment functions vary among populations. The MSY for a population is determined by its productivity and sources and magnitudes of densitydependent mortality rates, which reflect the life history of the species and the specific habitat in which the population lives.
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From page 282... ...
Differences in productivity between natural populations cause the same problem, and by-catch of other species in fisheries that are directed at a more productive species is an analogous problem. When fishing occurs on a mixture of populations with different stock-recruitment functions and fishing cannot be regulated at a rate appropriate for each component population, the stage is set for overfishing of the less-productive components (Ricker 1958, 1973; Hilborn 19853.
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From page 283... ...
Although MSY concepts have provided the basic paradigm for salmon management since the l950s, the paradigm has been inadequate, given the fishing pressure and economic development in the Pacific Northwest. Mixed-population fisheries, habitat change, and uncertain assessment advice have all contributed to overfishing and loss of less-productive populations.
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From page 284... ...
(Gordon 1954, Scott 1955, Crutchfield and Pontecorvo 19691. However, salmon fishing in the Pacific Northwest is not now (and has not been for a long while)
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From page 285... ...
Given the poor quality of the data available on almost all Pacific salmon populations, we cannot test the stock-recruitment theory rigorously. We have learned that the theory is more applicable in freshwater phases of salmon life history and that environmental variability in the marine habitat ultimately can determine the number of returning adults.
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From page 290... ...
Should fishing be stopped for Alaska salmon fishers whose runs are generally in much better shape than those returning to the Columbia River? The position of Alaska salmon fishers is that salmon problems in the Pacific Northwest are due to choices made by people of the Pacific Northwest and that Alaskans should not be penalized to fix the region's problems (Pacific Salmon Commission 1993a)
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From page 291... ...
However, it would be fought by all those affected. Another variant of this option would be to close all ocean fisheries in the Pacific Northwest.
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From page 292... ...
Alaskan fishers catch salmon destined for Alaska and British Columbia streams, as well as for the Columbia River and the north coastal area. Alaskan ocean fishers question why their opportunity to fish for healthy Alaskan populations should be jeopardized by habitat and hydropower problems in the Pacific Northwest.
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From page 293... ...
The committee starts by identifying several premises based on its experience: · In Pacific salmon, the presence of many diverse, spatially distributed spawning populations is closely aligned with genetic diversity, maximal use of available habitat, and potential for increasing production from natural spawners. The sustainable exploitation rate is a function of a population's productivity determined over all life phases.
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From page 294... ...
The critical elements are sound biological advice, explicit and assessable management objectives (biological, social, economic, etc.) , an institutional process for developing management plans, control of fisheries, and accountability in achieving management objectives.
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From page 295... ...
In summary, the committee recommends the establishment of minimum safe levels of spawning escapements to reduce the risk of continued loss of salmon populations and production. Actual escapements should always exceed this value, with allowances for assessment error for abundances near this minimum level.
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From page 296... ...
Genetic diversity provides for the continuing evolutionary process and is the biological basis of future salmon production. Therefore, the committee recommends managing for the joint biological objectives of MSE and increased diversity within and between local breeding populations, which will result in increased production in the long run.
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From page 297... ...
297 X ~ id ~ ~1 o o · Ct Ct Pa / / i 2 1 / .'' \ , ".
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From page 298... ...
Surveys would be designed to be repeatable annually and to measure quantitatively the spatial and temporal diversity of local breeding populations. · Conduct of annual evaluations involving quantitatively assessed indicator populations, surveys of the spatial and temporal diversity of local breeding populations within geographic areas, and fishery dynamics.
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From page 299... ...
The use of adaptive management, however, emphasizes the reed for effective institutional processes for communication and participation in the development of longer-term management plans. Control of Fisheries Meeting the joint management objectives of achieving the MSE and increasing diversity of local breeding populations diversity will not resolve the mixedpopulation fishing problem or settle allocation debates.
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From page 300... ...
Fishers should recall, however, that fishing at a lower rate on an increasing population will eventually restore catch levels. Developing fishing plans for each of the Pacific Northwest regions will necessitate consideration of specific resource problems, distribution of fisheries, and social groups.
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From page 301... ...
and operate at sustainable exploitation rates. Even after a population has recovered, managers and users should not expect a return to historic exploitation levels, because those were based on excessive fishing rates.
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