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

Randall M. Peterman,Brigitte Dorner,Gregory T. Ruggerone,Katherine W. Myers

doi:10.1577/c09-054.1

Abstract

AbstractAbundance 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.

Highlights

Abstract.—–Abundance estimates of wild and hatchery Pacific salmon Oncorhynchus spp. are important for evaluation of stock status and density-dependent interactions at sea
Wild pink salmon abundance declined from the 1950s through the early 1970s; in the 29 years after the 1976–1977 ocean regime shift, wild pink salmon abundance increased by an average of 90% compared with the previous 15 years (Figure 2A)
In contrast to pink salmon and sockeye salmon, wild chum salmon abundance did not increase after the 1976–1977 ocean regime shift, and from 1980 to 2005 wild abundance was lower than that estimated for the 1950s

Summary

Introduction

Abstract.—–Abundance estimates of wild and hatchery Pacific salmon Oncorhynchus spp. are important for evaluation of stock status and density-dependent interactions at sea. During 1990–2005, annual production of hatchery-origin adult salmon averaged 78 3 106 chum salmon, 54 3 106 pink salmon, and 3.2 3 106 sockeye salmon, or approximately 62, 13, and 4%, respectively, of the combined total wild and hatchery salmon abundance. In light of the evidence for density-dependent processes and the broad distributions of salmon stocks at sea, it is important for fishery scientists and SALMON ABUNDANCE IN THE NORTH PACIFIC managers to consider total salmon abundance and competitive interactions among wild and hatchery salmon in the North Pacific Ocean Knowledge of such density-dependent processes may be essential for achieving harvest or spawning objectives and for maintaining productive wild salmon populations in the North Pacific Ocean (Peterman 1991). Previous estimates exist for wild and hatchery salmon catches and spawner abundances throughout the North Pacific

Objectives

Methods

Results

Conclusion