Until recently, northern Bering Sea ecosystems were characterized by extensive seasonal sea ice cover, high water column and sediment carbon production, and tight pelagic-benthic coupling of organic production. Here, we show that these ecosystems are shifting away from these characteristics. Changes in biological communities are contemporaneous with shifts in regional atmospheric and hydrographic forcing. In the past decade, geographic displacement of marine mammal population distributions has coincided with a reduction of benthic prey populations, an increase in pelagic fish, a reduction in sea ice, and an increase in air and ocean temperatures. These changes now observed on the shallow shelf of the northern Bering Sea should be expected to affect a much broader portion of the Pacific-influenced sector of the Arctic Ocean.

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Pink salmon Onchorhynchus gorbuscha with identifiable thermal otolith marks from Prince William Sound hatchery release groups during 2001 were used to test the hypothesis that faster-growing fish during their first summer in the ocean had higher survival rates than slowergrowing fish. Marked juvenile pink salmon were sampled monthly in Prince William Sound and the Gulf of Alaska, and adults that survived to maturity were recovered at hatchery release sites the following year. Surviving fish exhibited significantly wider circuli spacing on the region of the scale formed during early marine residence than did juveniles collected at sea during their first ocean summer, indicating that marine survival after the first growing season was related to increases in early marine growth. At the same circuli, a significantly larger average scale radius for returning adults than for juveniles from the same hatchery would suggest that larger, fastergrowing juveniles had a higher survival rate and that significant size-selective mortality occurred after the juveniles were sampled. Growth patterns inferred from intercirculi spacing on scales varied among hatchery release groups, suggesting that density-dependent processes differed among release groups and occurred across Prince William Sound and the coastal Gulf of Alaska. These observations support other studies that have found that larger, faster-growing fish are more likely to survive until maturity.

Allozymes from 46 loci were analyzed from chum salmon (Oncorhynchus keta) collected at 61 locations in southeast Alaska and northern British Columbia. Of the 42 variable loci, 21 had a common allele frequency <0.95. We observed significant heterogeneity within and among six regional groups: central southeast Alaska, Prince of Wales Island area, southern southeast Alaska – northern British Columbia, north-central British Columbia, and two groups in the Queen Charlotte Islands. Genetic variation among regions was significantly greater than within regions. The three island groups were distinct from each other and from the mainland populations. Allele frequencies were stable over time in 14 of 15 locations sampled for more than 1 yr. The geographic basis for heterogeneity among regions is confounded in part by spawning-time differences. The Prince of Wales and Queen Charlotte populations spawn in the fall; the mainland populations spawn mainly in the summer, although some overlap exists. Overall, most genetic diversity (97%) occurred within sampling locations; the remaining diversity was distributed almost equally within and among regions. Our genetic data may provide fishery managers a means to estimate stock composition in the mixed-stock fisheries near this boundary between the United States and Canada.

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To better understand how densitydependent growth of ocean-dwelling Pacific salmon varied with climate and population dynamics, we examined the marine growth of sockeye salmon Oncorhynchus nerka in relation to an index of sockeye salmon abundances among climate regimes, population abundances, and body sizes under varied lifehistory stages, from 1925 to 1998, using ordinary least squares and multivariate adaptive regression spline threshold models. The annual marine growth and body size during the juvenile, immature, and maturing life stages were estimated from growth pattern increments on the scales of adult age 2.2 sockeye salmon that returned to spawn at Karluk River and Lake on Kodiak Island, Alaska. Intra-specific density-dependent growth was inferred from inverse relationships between growth and sockeye salmon abundance based on commercial harvest. Density-dependent growth occurred in all marine life stages, during the cool regime, at lower abundance levels, and at smaller body sizes at the start of the juvenile life stage. The finding that density dependence occurred during the cool regime and at low population abundances suggests that a shift to a cool regime or extreme warm regime at higher population abundances could further reduce the marine growth of salmon and increase competition for resources. OPEN PEN ACCESS CCESSGrowth patterns on the scales of maturing sockeye salmon record density-dependent and density-independent freshand saltwater conditions. Photo: Masahide KaeriyamaMar Ecol Prog Ser 370: [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] 2008 were linked to fluctuations in regional climate and basin-scale variations in ocean conditions (Royal & Tully 1961, Cushing 1971, Scarnecchia 1981, Beamish & Bouillon 1993, Mueter et al. 2005. Climatic and oceanic variations have also been associated with fluctuations in Atlantic salmon Salmo salar abundance and catches in Iceland (Scarnecchia 1984, Scarnecchia et al. 1989), Ireland (Boylan & Adams 2006), and Norway and Scotland (Friedland et al. 2000). During the 20th century, climatic and oceanic conditions in the North Pacific have undergone large fluctuations, with 2 distinct warm regimes (1925 to 1946 and 1977 to 1998) and a cool regime (1947 to 1976) (Mantua & Hare 2002). Warm regimes were characterized by a deepening and eastward shift in the Aleutian Low Pressure cell, increased winter storm activity, increased atmospheric circulation, below normal seasurface temperatures (SSTs), increased upwelling of nutrient-rich waters in the central North Pacific Ocean; above normal SSTs, higher precipitation, weaker downwelling in the coastal Gulf of Alaska; and weaker upwelling in coastal waters off the continental United States. The cool regime was characterized by the opposite conditions (Trenberth & Hurrell 1994).Climate and oceanic variations have been linked to concurrent variations in Pacific salmon production. Cool regimes, in part due to increased coastal upwelling of nutrient-rich, cooler waters, favor salmon prod...

The National Marine Fisheries Service (NMFS) is charged with restoring and protecting anadromous Pacific salmon stocks in all habitats of U.S. waters, including their period of residence in estuarine and oceanic waters. Recent studies have implicated the estuarine and coastal phase of the salmon life cycle as being of equal importance to the freshwater phase in determining production. Evaluation of the freshwater phase of salmon has yielded a better understanding of the factors limiting production in this environment; however, a comparable understanding in the marine environment is lacking. Currently, some marine salmon research is being conducted at various NMFS labs on the West Coast, but there has been little attempt to coordinate activities among the different regions. In response, we propose a comprehensive plan to address ocean and estuarine survival of salmon by identifying research needs and suggesting ways to meet these needs. We recommend that NMFS research focus on (1) distribution and movement patterns of salmon in marine waters, (2) health and condition of hatchery and wild salmon, (3) trophic dynamics of salmon, and (4) large‐scale effects of the atmosphere and ocean.

Examples of desired genetic changes produced in fish by selective breeding are contrasted with those of unintentional and often harmful genetic changes resulting from artificial propagation over prolonged periods, e.g. reduced longevity and reduced temperature tolerance. Evidence for undesired effects caused by the hatchery environment on captive fish stocks is also presented, e.g. precocity, inappropriate feeding behavior, and the risks posed by artificial rearing techniques are discussed. Methods for identifying both genetic and environmentally induced changes are outlined along with experimental designs for distinguishing between them. Some practical recommendations are offered for establishing, developing, and maintaining brood stocks in hatcheries and for managing wild fish populations in ways that maximize genetic variability while avoiding the occurrence of undesirable changes. Adherence to the recommended procedures will improve progress in fisheries rehabilitation efforts.Key words: fish culture, genetics, environmental effects, brood stocks, resource management