Effects of egg size, larval growth rate, and juvenile nutritional condition on population dynamics of walleye pollock

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07834
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Hokkaido University
• Principal Investigator: TAKATSU Tetsuya 北海道大学, 水産科学研究院, 教授 (50241378)
• Research Collaborator: NAKAYA Mitsuhiro
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 卵 / 仔魚 / 稚魚 / 栄養状態 / 着底 / 輸送 / 吹送流 / 噴火湾

Outline of Final Research Achievements

To clarify survival processes in Japan Pacific Stock (JPS) of walleye pollock Gadus chalcogrammus, maternal effect and somatic condition were investigated in Funka Bay in 2016-2018. No annual difference in hatch-check diameter on larval otolith derived from maternal was observed between three year-classes. Notochord lengths in late February and early March were small in low water temperature years. The 75-77% of settled juveniles collected in mid-June have settlement checks around their otoliths and settled fork-lengths were estimated at 67.2-69.0 mm from the relationship between fork length and otolith diameter. Feeding intensities and somatic conditions of juveniles decreased in Tsugaru Warm Current water from August to October, then those recovered with water temperature decreasing after October. Annual fluctuations of somatic condition and growth rate might influence the recruitment of JPS.

Free Research Field

魚類生産生態学

Academic Significance and Societal Importance of the Research Achievements

噴火湾のスケトウダラの初期生残に及ぼす影響は、各発育段階で様々な要因が影響していることが明らかとなった。従って特定の発育段階の生残率に影響を及ぼす単独の要因だけで、資源量変動を解明することはかなわないだろう。ただし実際問題として、人間が天然のスケトウダラ資源の資源量変動に介入できる機会は、資源量変動が小さい未成魚期から成魚期にかけての漁獲管理しかない。また、現状では母親効果が影響を及ぼすほど高齢な雌親魚を十分獲り残していない可能性がある。従って今後は、卵質が高く生存しやすい卵を産卵する親魚の特定を急ぎ、そのような親魚の漁獲の制限が必要と考えられる。