2022 Fiscal Year Final Research Report
Elucidation of the autumn silvering mechanism of masu salmon in the Kyushu Island and establishment of artificial silvering induction technology using light.
| Project/Area Number |
20K06240
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 40040:Aquatic life science-related
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| Research Institution | University of Miyazaki |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 銀化 / 海水適応 / ヤマメ / サクラマス / 海面養殖 / 甲状腺ホルモン / 光周性因子 |
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| Outline of Final Research Achievements |
The landlocked masu salmon in Kyushu Island turns slightly silvery, or smolting in autumn. They become seedlings for cherry salmon seawater (SW) aquaculture in the coastal areas of Miyazaki, which is limited to the winter season. However, the smolting ratio is quite low, and their SW adaptability is incomplete. Overcoming these problems is the key to improving the efficiency of SW aquaculture. In the present study, we have physiologically investigated the fall smolting phenomenon of masu salmon in Kyushu Island.
Our results show that activation of the thyroid gland was observed in autumn, and that SW adaptability was acquired in early winter, and silvering and SW adaptability declined in spring. In addition, breeding masu salmon from Hokkaido, which is considered to be spring smolting strains, in Kyushu suggest that genetic factors, rather than environmental factors such as day length, contributed to the initiation of silvering among different strains of masu salmon.
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| Free Research Field |
魚類生理学
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| Academic Significance and Societal Importance of the Research Achievements |
サケ科魚類の銀化には、下垂体を中枢とした内分泌因子が関連することが、春に銀化する北方系統ヤマメや大西洋サケで知られているが、短日化の進行する秋に銀化する九州山系ヤマメではそれらの知見は乏しい。また、銀化発動時期の異なる系統ヤマメを同一の環境条件で飼育し、銀化変態や海水適応能を比較解析した事例も無い。本研究の成果は、単に、秋銀化に伴う内分泌系の機能発現の理解だけに留まらず、日長や光波長といった環境因子の入力と受容、脳内の光周性因子や内分泌因子の機能発現という一連の生理・内分泌機構として体系的に捉えるための基盤成果になり、将来的には、環境因子を基盤とした人為的な銀化誘導技術の確立にも直結する。
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