Magnitude and Trends in Abundance of Hatchery and Wild Pink Salmon, Chum Salmon, and Sockeye Salmon in the North Pacific Ocean

Abstract

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.

Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

“…Observed total scale size was higher during 1968 to 1980 than after 1980 when the biomass of competing salmon increased. Higher biomass resulted from increased hatchery production and improved survivals resulting from favourable ocean conditions (Eggers 2009;Ruggerone et al 2010a). Reductions in average body size after 1980 were observed in Pacific salmon from both North American and Asian populations (Bigler et al 1996;Helle and Hoffman 1998), suggesting a role of common factors such as density-dependent effects.…”

Understanding Smolt Survival Trends in Sockeye Salmon

“…Yet continued increases in hatchery salmon releases in Asia after 1991, as well as improved survival for many hatchery fish resulting from the release of larger or better-adapted young salmon (Dushkina 1994;Morita et al 2006;Kaev and Ignatiev 2007), resulted in increasing salmon biomass. Proportions of hatchery-origin fish in the North Pacific have been increasing since 1990 and constitute 50-62% of the total Chum Salmon, 10-13% of the Pink Salmon, and 4-10% of the Sockeye Salmon in the North Pacific Ocean (Ruggerone et al 2010;Kaeriyama et al 2012). Eggers (2009) estimated that at least 39% of the salmon biomass in a recent 10-year period was made up of hatchery-origin Pink and Chum Salmon.…”

“…Their recent abundance in the Pacific Ocean, as reflected by commercial catch, is as high as it has ever been (Irvine and Fukuwaka 2011). Global abundances are driven primarily by Pink Salmon O. gorbuscha and Chum Salmon O. keta, as well as, particularly in the eastern North Pacific Ocean, by Sockeye Salmon O. nerka (Eggers 2009;Ruggerone et al 2010;Irvine and Fukuwaka 2011). The status of Sockeye Salmon populations varies among regions however, and in British Columbia's Fraser River, low Subject editor: Suam Kim, Pukyong National University, Busan, South Korea *Corresponding author: james.irvine@dfo-mpo.gc.ca Received February 8, 2013; accepted July 24, 2013 numbers of returning salmon in recent years are a major concern (Grant et al 2011;Rand et al 2012).…”

“…Although others (Eggers 2009;Ruggerone et al 2010) have combined catch and spawner escapement data to develop run size biomass estimates for salmon, statistical comparisons between the time series generated by these approaches have not been made. We worked with data for Sockeye Salmon as well as for Pink and Chum Salmon since these were the most abundant salmon species and density-dependent interactions among them may be occurring (Ruggerone et al 2010). Data were aggregated for the northeast Pacific (North America) and northwest Pacific (Asia).…”

“…In the case of Fraser River Sockeye Salmon, Connors et al (2012) concluded the effect of competition with Pink Salmon could be exacerbated if Sockeye Salmon were exposed to farmed salmon during their out-migration, particularly during warm ocean conditions. Ruggerone et al (2010) and others have raised concerns that density-dependent interactions in the ocean resulting from hatchery releases may reduce Pacific salmon growth and survival.…”