Numerical abundance and biomass values presented here for Pink Salmon Oncorhynchus gorbuscha, Chum Salmon O. keta, and Sockeye Salmon O. nerka in the North Pacific Ocean span 90 years , representing the most comprehensive compilation of these data to date. In contrast to less populous species of salmon, these species are more abundant now than ever, averaging 665 × 10 6 adult salmon each year (1.32 × 10 6 metric tons) during 1990-2015. When immature salmon are included, recent biomass estimates approach 5 × 10 6 metric tons. Following an initial peak during 1934-1943, abundances were low until the 1977 regime shift benefited each species. During 1990-2015, Pink Salmon dominated adult abundance (67% of total) and biomass (48%), followed by Chum Salmon (20%, 35%) and Sockeye Salmon (13%, 17%). Alaska produced approximately 39% of all Pink Salmon, 22% of Chum Salmon, and 69% of Sockeye Salmon, while Japan and Russia produced most of the remainder. Although production of natural-origin salmon is currently high due to generally favorable ocean conditions in northern regions, approximately 60% of Chum Salmon, 15% of Pink Salmon, and 4% of Sockeye Salmon during 1990-2015 were of hatchery origin. Alaska generated 68% and 95% of hatchery Pink Salmon and Sockeye Salmon, respectively, while Japan produced 75% of hatchery Chum Salmon. Salmon abundance in large areas of Alaska (Prince William Sound and Southeast Alaska), Russia (Sakhalin and Kuril islands), Japan, and South Korea are dominated by hatchery salmon. During 1990-2015, hatchery salmon represented approximately 40% of the total biomass of adult and immature salmon in the ocean. Density-dependent effects are apparent, and carrying capacity may have been reached in recent decades, but interaction effects between hatchery-and natural-origin salmon are difficult to quantify, in part because these fish are rarely separated in catch and escapement statistics. The following management changes are recommended: (1) mark or tag hatchery salmon so that they can be identified after release, (2) estimate hatchery-and natural-origin salmon in catches and escapement, and (3) maintain these statistics in publicly accessible databases.

Well-functioning food webs are fundamental for sustaining rivers as ecosystems and maintaining associated aquatic and terrestrial communities. The current emphasis on restoring habitat structure-without explicitly considering food webs-has been less successful than hoped in terms of enhancing the status of targeted species and often overlooks important constraints on ecologically effective restoration. We identify three priority food web-related issues that potentially impede successful river restoration: uncertainty about habitat carrying capacity, proliferation of chemicals and contaminants, and emergence of hybrid food webs containing a mixture of native and invasive species. Additionally, there is the need to place these food web considerations in a broad temporal and spatial framework by understanding the consequences of altered nutrient, organic matter (energy), water, and thermal sources and flows, reconnecting critical habitats and their food webs, and restoring for changing environments. As an illustration, we discuss how the Columbia River Basin, site of one of the largest aquatic/riparian restoration programs in the United States, would benefit from implementing a food web perspective. A food web perspective for the Columbia River would complement ongoing approaches and enhance the ability to meet the vision and legal obligations of the US Endangered Species Act, the Northwest Power Act (Fish and Wildlife Program), and federal treaties with Northwest Indian Tribes while meeting fundamental needs for improved river management.

The importance of interspecific competition as a mechanism regulating population abundance in offshore marine communities is largely unknown. We evaluated offshore competition between Asian pink salmon and Bristol Bay (Alaska) sockeye salmon, which intermingle in the North Pacific Ocean and Bering Sea, using the unique biennial abundance cycle of Asian pink salmon from 1955 to 2000. Sockeye salmon growth during the second and third growing seasons at sea, as determined by scale measurements, declined significantly in odd‐numbered years, corresponding to years when Asian pink salmon are most abundant. Bristol Bay sockeye salmon do not interact with Asian pink salmon during their first summer and fall seasons and no difference in first year scale growth was detected. The interaction with odd‐year pink salmon led to significantly smaller size at age of adult sockeye salmon, especially among younger female salmon. Examination of sockeye salmon smolt to adult survival rates during 1977–97 indicated that smolts entering the ocean during even‐numbered years and interacting with abundant odd‐year pink salmon during the following year experienced 26% (age‐2 smolt) to 45% (age‐1 smolt) lower survival compared with smolts migrating during odd‐numbered years. Adult sockeye salmon returning to Bristol Bay from even‐year smolt migrations were 22% less abundant (reduced by 5.9 million fish per year) compared with returns from odd‐year migrations. The greatest reduction in adult returns occurred among adults spending 2 compared with 3 years at sea. Our new evidence for interspecific competition highlights the need for multispecies, international management of salmon production, including salmon released from hatcheries into the ocean.

Abundance estimates of wild and hatchery Pacific salmon Oncorhynchus spp. are important for evaluation of stock status and density‐dependent interactions at sea. We assembled available salmon catch and spawning abundance data for both Asia and North America and reconstructed total abundances of pink salmon O. gorbuscha, chum salmon O. keta, and sockeye salmon O. nerka during 1952–2005. Abundance trends were evaluated with respect to species, regional stock groups, and climatic regimes. Wild adult pink salmon were the most numerous salmon species (average = 268 × 106 fish/year, or 70% of the total abundance of the three species), followed by sockeye salmon (63 × 106 fish/year, or 17%) and chum salmon (48 × 106 fish/year, or 13%). After the 1976–1977 ocean regime shift, abundances of wild pink salmon and sockeye salmon increased by more than 65% on average, whereas abundance of wild chum salmon was lower in recent decades. Although wild salmon abundances in most regions of North America increased in the late 1970s, abundances in Asia typically did not increase until the 1990s. Annual releases of juvenile salmon from hatcheries increased rapidly during the 1970s and 1980s and reached approximately 4.5 × 109 juveniles/year during the 1990s and early 2000s. During 1990–2005, annual production of hatchery‐origin adult salmon averaged 78 × 106 chum salmon, 54 × 106 pink salmon, and 3.2 × 106 sockeye salmon, or approximately 62, 13, and 4%, respectively, of the combined total wild and hatchery salmon abundance. The combined abundance of adult wild and hatchery salmon during 1990–2005 averaged 634 × 106 salmon/year (498 × 106 wild salmon/year), or approximately twice as many as during 1952–1975. The large and increasing abundances of hatchery salmon have important management implications in terms of density‐dependent processes and conservation of wild salmon populations; management agencies should improve estimates of hatchery salmon abundance in harvests and on the spawning grounds.

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