Opportunistic feeding habit of swordtip squid Uroteuthis edulis by areas, seasons and capture methods

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K07844
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Nagasaki University
• Principal Investigator: MATSUSHITA Yoshiki 長崎大学, 水産・環境科学総合研究科(水産), 教授 (30372072)
• Co-Investigator(Kenkyū-buntansha): 菅 向志郎 長崎大学, 水産・環境科学総合研究科(水産), 准教授 (60569185)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: ケンサキイカ / 漁法 / 餌生物 / 空胃率 / 共食い / DNA分析

Outline of Final Research Achievements

We collected 715 individuals of swordtip squid Uroteuthis edulis from fisheries that used towed gear, setnet and jig fishing with artificial light in the East China Seas and the western part of the Sea of Japan. Their stomach contents were analyzed by DNA base sequencing. We also analyzed ratios of empty stomach and cannibalization by using the GLM logistic analysis. The empty stomach ratio was influenced by areas, depths and fishing methods while the cannibalization ratio was influenced by the fishing methods.
From the stomach content analysis by DNA base sequencing, we identified 28 fish species and 5 invertebrates. The most observed species was Japanese anchovy Engraulis japonicus (22%), followed by swordtip squid (15%) and banded blue sprat Spratelloides gracilis (11%). In addition, high commercial value species including tiger puffer Takifugu rubripes and yellowtail Seriola quinqueradiata were found.

Free Research Field

漁業生産工学

Academic Significance and Societal Importance of the Research Achievements

イカ類は鋭い口器を用いて餌を食べるため，検鏡による胃内容物の観察，特定は難しく，西日本における重要なイカ資源であるケンサキイカの食性については少数の地域で定性的な観察結果の報告しか無かった。本研究により，広い水域においてケンサキイカの食性が詳細に明らかになった。そして餌生物の中には水産重要種で高次捕食者でもあるブリ，マハタ，クエ，マルソウダ，ヒラソウダ，トラフグが含まれたことも初めて示された。しかしこれらの観察数は少なかった。