Current and Future Management of Salmon Stock Enhancement Programs in Japan

Stock enhancement is one of the useful approaches for fishery management. In Japan, chum salmon Oncorhynchus keta stocks have been supported by hatchery programs that constitute one of the largest hatchery programs in the world. The program is successful for the purpose of increasing commercial catches; nevertheless many subjects remain to be examined for the program. Recently, a distinct difference in return rates among regions has emerged. It may be caused by environmental conditions; however, the causal factors have not been understood. At present, there has been no evidence of any decrease of genetic diversity in chum salmon despite the intensive hatchery programs. However, attention and efforts to further minimize genetic and ecological disturbance are essential because loss of rare alleles and decline in the survivals has been reported in the case of other enhanced species (e.g., red sea bream Pagrus major). Management efforts have been devoted to hatchery programs rather than naturally spawning chum salmon in Japan, but assessment of naturally spawning populations recently commenced. Although it is important to conduct the hatchery programs effectively to support commercial chum salmon stocks, a proper management policy should be established to conserve the remaining naturally spawning chum salmon populations in Japan.