Do Hatchery Salmon Affect the North Pacific Ocean Ecosystem?

Releases of hatchery-reared anadromous salmon into the North Pacific Ocean are currently estimated between 5 and 6 billion juveniles per year. Wild spawning salmon may produce an additional 4 to 5 times this number of juveniles. With as many as 25 billion juvenile Pacific salmon annually entering the ocean and currently producing over 1. 0 million mt of returning adults, salmon survival and production in the North Pacific Ocean is currently at historically high levels in spite of depressed runs and endangered stocks in some regions. Biological changes in size and age at maturity of some stocks have raised questions on the density effects of high abundance, and on the long-term well being and health of salmon stocks. Changes in size and age notwithstanding, favorable ocean conditions for survival and growth, even growth at reduced levels, have produced historic numbers and biomass of salmon suggesting the evidence for limitations in the carrying capacity for these fishes is inconclusive. Important studies are underway in several countries to better understand the effects of hatchery-wild stock interactions on the spawning grounds but little attention has been directed toward this issue in the ocean. New mass marking and identification technologies for both hatchery and wild fish provide mechanisms for investigating the interactions of salmon in the open ocean. Given biological concerns about ocean carrying capacity and socio-economic issues associated with record runs, should NPAFC member countries consider cooperative quotas to limit production of salmon around the North Pacific Rim? If implemented, each country could determine what portion of its quota would be derived from wild and hatchery production.