Japanese chum salmon stock enhancement: current perspective and future challenges

Shuichi Kitada

doi:10.1007/s12562-013-0692-8

Abstract

This study reviews the present status of the Japanese chum salmon Oncorhynchus keta stock enhancement program and considers the ecological sustainability of wild populations while providing fishery production, exemplified by the hatchery-based Kitami region set net fishery. The return rate and the number of returns have been historically high in the Sea of Okhotsk, but have decreased in other regions since 2005. Natural spawning of chum salmon occurred in at least 160 rivers in Hokkaido. The genetic diversity of Japanese chum salmon was similar to or higher than that of other Pacific Rim populations. Numbers of alleles were high at microsatellite loci, but the loss of rare haplotypes was observed in all populations. The estimated Ne/N ratio for the Kitami region was >0.15 % including hatchery and wild fish under the present high fishing pressure. Four regional populations were inferred in Hokkaido, however, genetic differentiation was weak and some river-populations were nested. Substantial changes in run timing were observed, but it has recovered gradually owing to the recent practice of escapement. Our analyses highlight the importance of juvenile quality and the vital roles of escapements in enhanced and non-enhanced rivers. New research is needed to minimize the genetic risks associated with hatchery programs.

Highlights

The hatchery stock enhancement program in Japan was initiated in the 1880s to increase Japanese chum salmon Oncorhynchus keta fishery production and has continued for over 120 years
Current wild salmon escapement (20,191) was *0.1 % of the 18,460,000 fish returned to the Kitami region in September–November, which was an underestimate because it did not account for naturally spawning salmon in major enhanced rivers (SFFRI, pers. comm.)
Transgenesis of the growth hormone gene causes inferior reproductive behavior and reduces fertilization success of Atlantic salmon [55]. These findings provide an important suggestion that enhanced growth in captivity causes a reduction in reproductive performance of hatchery fish

Summary

Introduction

The hatchery stock enhancement program in Japan was initiated in the 1880s to increase Japanese chum salmon Oncorhynchus keta fishery production and has continued for over 120 years. Fish Sci (2014) 80:237–249 wild populations, focusing on the hatchery-based set net fishery in the Kitami region, Hokkaido, the largest chum salmon fishery in Japan. After conducting a brief review of the chum salmon stock enhancement program and the results of wild fish counting surveys in Hokkaido, the ratio of effective population size to the number of returning adult fish was estimated for the Kitami region by combining hatchery broodstock and hatchery/wild escapements.

Results

Conclusion