Clarification of physiological mechanism of fall smoltification in Pacific salmon and its application for screening of seedlings

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K07572
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic life science
• Research Institution: Miyagi University of Education
• Principal Investigator: Munakata Arimune 宮城教育大学, 教育学部, 准教授 (10361213)
• Research Collaborator: Shimizu Munetaka ; Yada Takashi ; Hiroi Junya ; Schreck Carl ; Noakes David
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: サクラマス / マスノスケ / 降海期多型 / スモルト / 銀化変態 / サロゲート / HSP70 / コルチゾル

Outline of Final Research Achievements

In general, Pacific salmon such as masu and Chinook salmon undergo smoltification and seaward migration in spring. Recently, however, some populations show such phenomena in fall. According to our studies, fall smolt masu salmon show high plasma thyroid hormone levels as well as spring smolt, suggesting that fall smolt undergo the smoltification using same physiological mechanisms. Since fall smolt masu salmon showed high growth rate, it is also suggested that growth system modulate early smoltification. In Chinook salmon, furthermore, fall smolts exhibited high levels of plasma cortisol levels and HSP70 gene expression in the liver against water temperature decrease and increase. Based on these results, its is indicated that water temperature changes modulate early smoltification. We also developed the selection methods of fall smolts by use of hatchery cultured juvenile masu and Chinook salmon.

Free Research Field

魚類行動生理学

Academic Significance and Societal Importance of the Research Achievements

従来よりも約半年程度早く銀化変態を行う秋スモルトを用いることで、サクラマスやマスノスケなどの海面養殖をより早期に開始することができ、これまでよりも短期間、かつ低コストで太平洋サケの中間育成を行うことができると期待される。これにより、近年外国産サーモンに押されている国内サケ養殖の活性化に繋がることが期待される。また秋にスモルト化する太平洋サケは国内外の複数の河川に自然分布していることから、これらの出現の機構を知り、将来の保全や資源管理に資することが期待される。