The science is debatable
https://wdfw.wa.gov/sites/default/files/publications/01947/wdfw01947.pdf
Page 68.
Harvest Constraint Cannot Effect Recovery. Recovery for most populations cannot be accomplished solely by constraint of harvest. For the immediate future, harvest constraint will assist in providing optimal escapement, suited to current habitat condition. Productivity is constrained by habitat condition, and is not influenced by harvest, providing harvest does not reduce escapement to the point of demographic or genetic instability. The quality and quantity of freshwater and estuarine environment determines embryonic and juvenile survival, and oceanic conditions influence survival up to the age of recruitment to fisheries. Physical or climatic factors, such as stream flow during the incubation period, will vary annually, and have been shown to markedly reduce smolt production in some years. The capacity of Chinook salmon to persist under these conditions is primarily dependent on their diverse age structure and life history, and habitat factors (e.g. channel structure, offchannel refuges, and watershed characteristics that determine runoff) that mitigate adverse conditions. For several Puget Sound populations, mass marking of hatchery production has enabled accurate accounting of the contribution of natural- and hatchery-origin adults to natural escapement. Sufficient data has accumulated to conclude that a significant reduction of harvest rates, and increased marine survival in some years, has increased the number of hatchery-origin fish that return to spawn, whereas returns of natural-origin Chinook salmon, though stable, have not increased. Abundance (escapement) data for the North Fork Nooksack, Skokomish, Skykomish, and Dungeness rivers shows NOR returns have remained at very low levels, while total natural escapement has either increased or held stable where hatchery supplementation programs exist. Skokomish River spawner abundance data is presented as an example of this trend (Figure 6-2). It is evident that natural production has not increased under reduced harvest pressure, and is constrained primarily by the condition of freshwater habitat.
Therefore, the harvest rates governed by this plan are not impeding recovery. Harvest constraint has, for most populations, contributed to stable or increasing trends in escapement. For many populations this includes a large proportion of hatchery-origin adults. But stable or negative trends in NOR returns strongly suggests that recruitment will not increase substantially unless constraints limiting freshwater survival are alleviated.
Page 44.
Rules for Allowing Fisheries. For the purposes of this Plan, “directed” fisheries are defined as those in which more than 50 percent of the total fishery-related mortality is made up of ESA protected, Puget Sound-origin Chinook Salmon. Total mortality includes all landed and non-landed mortality. Landed and non-landed incidental mortality of ESA listed Chinook Salmon will occur in fisheries directed at other salmon species. Additional impacts will occur as a result of fisheries directed at hatchery-origin Chinook salmon, including mark-selective fisheries. In both cases the fisheries will be strictly constrained by harvest limits that are established expressly to conserve naturally-produced Chinook salmon. The annual management strategy, for any given Chinook salmon management unit, shall depend on whether a harvestable surplus is forecast. This Plan prohibits directed harvest on naturalorigin populations of Puget Sound Chinook Salmon, unless they have harvestable surplus. If a management unit does not have a harvestable surplus, fishery-related mortality will be constrained to incidental impacts. Similarly, in some cases constraints will be proposed to protect escapements of hatchery populations. Directed and incidental fishery impacts are constrained by specified exploitation rate ceilings or escapement goals for each management unit.
The following rules define how and where fisheries can operate:
· Fisheries may be conducted where more than 50 percent of the resulting fishery-related mortality will accrue to management units and species with harvestable surpluses.
· Within this constraint, the intent is to limit harvest of ESA protected Chinook salmon populations or management units that lack harvestable surplus and develop a fishing regime that will not exceed specified ceiling exploitation rates or escapement goals.
· Incidental harvest of weak stocks will not be eliminated, but to avoid increasing the risk of extinction of weak stocks, fishery-related impacts will be reduced to the minimal level that still enables fishing opportunity on non-listed and non-ESA protected Chinook and other species, when such harvest is appropriate.
· Exceptions may be provided for tribal ceremonial and/or subsistence fisheries, and research fisheries that collect information essential to management.
Where it is not possible to effectively target productive natural stocks or hatchery production, without exceeding specified harvest controls for runs without a harvestable surplus, use of the above rules will likely necessitate foregoing the harvest of much of the surplus from those more productive management units.