No abstract

This report summarizes a survey of healthy native stocks of anadromous salmonids in the Pacific Northwest and California. We used a questionnaire approach combined with spatial analysis to describe the status and distribution of stocks considered to be in relatively good condition. These stocks now constitute a small fraction of the region's historic anadromous salmonid resource but are critical to maintaining current resource productivity. Several agencies have developed, or are in the process of developing, computerized databases that will help organize predominantly quantitative data on native stocks of anadromous salmonids. Our survey supplements those efforts by summarizing some of the knowledge of biologists familiar with the stocks and by making status assessments that at times go beyond conservative analyses of quantitative data. The survey identified 99 healthy native wild stocks of salmon and steelhead that biologists consider to be at least one‐third as abundant as would be expected without human impacts, including 20 considered at least two‐thirds as abundant. More than three‐quarters of these stocks are fall chinook, chum salmon, or winter steelhead in Puget Sound or coastal watersheds of Oregon or Washington. Fewer healthy populations remain of summer steelhead and coho, pink, and sockeye salmon and spring or summer chinook. We suggest that healthy stocks provide unique opportunities for conservation and research that are at least as important to the future of the region's anadromous salmonids as those associated with at‐risk stocks.

This paper describes an ecosystem approach (the Bradbury framework) to prioritizing watersheds for watershed restoration and salmon recovery, and gives an example of its application. The framework was applied at three spatial scales (in descending order) to prioritize (1) river basins within the north coast geographic area of Oregon (USA), (2) watersheds within the Tillamook Bay basin, and (3) restoration activities at the watershed level. Implementing the framework identified the Nehalem and Tillamook Bay basins as high priority for the north coast of Oregon. Within the Tillamook Bay basin, the Wilson, Kilchis, and Trask river watersheds emerged as high priority. Preliminary analysis indicated that controlling sediment sources by addressing upland road conditions and allowing floodplain and riparian ecosystems to recover are highest priority protection and restoration activities within the Tillamook Bay basin. The sample application demonstrates that an ecosystem approach (the Bradbury framework) is particularly advantageous where data are limited, although previous identification of relatively intact areas is required. Implementing the framework is intended to lead to restoration of native species, but it may not provide immediate assistance for some species or populations of concern.

Stocks of striped bass Morone saxatilis have declined in the Chesapeake Bay system over the last decade. We present evidence for the working hypothesis that the decline has resulted, in part, from loss of deep-water habitat for adults, caused by limiting concentrations of dissolved oxygen that are related, in turn, to nutrient enrichment and greater planktonic production. A related hypothesis is that changes in the near-shore habitat for juvenile striped bass, involving severe declines in submerged aquatic vegetation due to nutrient-driven planktonic shading, also have contributed to the decline of striped bass. Nutrients (nitrogen and phosphorns) and chlorophyll a, an indicator of phytoplankton biomass, have increased in many areas of the bay and tributaries over the past 20 to 30 years. These trends are qualitatively correlated with greater deoxygenation of the deep channel in the mid and upper bay. During the late 1970s, summer oxygen concentrations as low as 2 ml/liter approached to within 7-8 m of the surface, allowing water stressful to striped bass to intrude onto shoal areas of the bay. The volume of Chesapeake Bay bottom waters containing 0.5 ml O2/liter or less was about 15 times greater in July 1980 than in July 1950. The combination of the expanding hypoxic pool and summer temperatures above preferred levels for adult striped bass may contribute to an "oxygen-temperature squeeze" that forces adults onto shoal areas of the bay or out of the upper bay. Many of these shoal areas now lack suitable cover for juvenile striped bass and their prey. Strong intraspecific competition among striped bass may be occurring there. Striped bass Morone saxatilis populations havedeclined for the past decade over much of their east-coast range, especially in Chesapeake Bay (Fig. 1). The decline appears to be related to a failure in year classes during the entire period since the last dominant one in 1970, which brought peak landings in 1973. The importance of the striped bass fishery to Chesapeake Bay and the effects of its decline elsewhere along the east coast has led to increased attention to this species by the United States Congress, state resource managers, and the research community. As referenced in this issue byCoutant (1985), numerous factors may contribute to the decline of striped bass stocks, and this makes it difficult I Principal affiliation: College of Marine Studies,

Over 300 native stocks of Pacific salmon, steelhead, and coastal cutthroat trout (Oncorhynchus spp.) are at risk of extinction in the Pacific Northwest. With only limited resources available for conservation and recovery, prioritization of these stocks may become necessary if meaningful measures are to be implemented. We propose criteria by which prioritization may be guided. First, we rank stocks for risk of extinction, either by population viability analysis or by a set of surrogate measures. Then we rank stocks for biological consequences of extinction, using sets of questions designed to establish the genetic and evolutionary consequences and the ecological consequences if a stock were to become extinct. Together, these rankings allow stocks to be prioritized for a range of possible actions, with those stocks at highest risk and bearing the greatest biological consequences of extinction receiving attention first. Application of the prioritization process to 20 Pacific anadromous salmonid stocks worked as intended, although data limitations are considerable. The process is most likely to work successfully when applied to many stocks on which data exist, when several experts carry out the prioritization, and when the results are peer reviewed.