Studies on stock fluctuation of seasonal cohorts of Japanese flying squid related to the success of reproduction and recruitment

2015 Fiscal Year Final Research Report

• Project/Area Number: 25292117
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Hokkaido University
• Principal Investigator: Sakurai Yasunori 北海道大学, 水産科学研究科(研究院), 特任教授 (30196133)
• Co-Investigator(Kenkyū-buntansha): YAMAMOTO Jun 北海道大学, 北方生物圏フィールド科学センター, 助教 (10292004)
• Project Period (FY): 2013-04-01 – 2016-03-31
• Keywords: スルメイカ / 再生産仮説 / 大型水槽 / 産卵行動 / ふ化幼生 / 有機懸濁物 / 気候変化 / 資源変動予測

Outline of Final Research Achievements

The experiment was conducted to test the reproductive hypothesis of Todarodes pacificus in a large tank (200 tons). The maturation process untill spawning were controled by temperatures during 13 and 20°C. Ripe females and males were released into the large tank.The egg masses were observed suspended in the thermocline. However, without the thermal gradient,egg masses collapsed on the bottom, and eggs were infested by microbes.Twenty-one females spawned 39 egg masses (30 to 120 cm diameter).The paralarvae survived for up to 13 days, which was suggested that they fed on DOM with marine bacteria.
Annual catches of fall cohort are gradually decreasing after 2000s.The inferred spawning area was covered by warm surface water above 24°C . However, annual catches of winter cohort are stable after 2000s. The inferred spawning area was formed along continental slope in the East China Sea. The fishing area shifted to more northern area and the southward migration was delayed by December.

Free Research Field

水産科学