Analysis of the hatching site and migratory behaviour of the swordtip squid (Uroteuthis edulis) caught in the Japan Sea and Tsushima Strait in autumn estimated by statolith analysis

Tadanori Yamaguchi, Yuji Kawakami, Michiya Matsuyama

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

In contrast to the swordtip squid (Uroteuthis edulis) caught in the spring and summer, those caught in the autumn in the Japan Sea and the Tsushima Strait are characterized by thick bodies with large clubs, long tentacles and large suckers. In addition, most females and many males are immature. However, the reasons for these characteristics, as well as the hatching site and migratory behaviour, are not well known. The empirical water temperature of juveniles was estimated at ∼17°C through strontium:calcium (Sr:Ca) ratios in statoliths and information on seawater temperature distribution. The ontogenetic variation in Sr:Ca ratios decreased from hatching to 60 days after hatching and then remained stable. The estimated water temperature was ∼21°C after 60 days. Thus, individuals of the autumn-migrating group most likely hatch in the southern East China Sea in the winter and early spring and then move north-eastwards with currents and pass through the Tsushima Strait into the southern Japan Sea during or after July. However, the squid could be present in these waters without strong currents northeast of Tsushima Island, where thermoclines occur during summer, and become confined in limited layers until vertical mixing occurs in the autumn. The distribution of the squid would thereafter extend to fishing grounds in the southern and south-eastern Japan Sea and then to the Tsushima Strait. This migratory behaviour could be the cause of the observed characteristics because bottom seawater temperatures are much lower in the Japan Sea than in the East China Sea.

Original languageEnglish
Pages (from-to)105-112
Number of pages8
JournalMarine Biology Research
Volume14
Issue number1
DOIs
Publication statusPublished - Jan 2 2018

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science

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