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<p>We aimed to clarify the spawning season, spawning grounds, and horizontal distribution patterns of <i>Physiculus japonicus</i> eggs and larvae on the basis of extensive ichthyoplankton surveys conducted along the Pacific coast of Japan from 2020 to 2024. Specimens were identified and classified on the basis of their morphological characteristics. Eggs and larvae were observed from January to April and showed consistent peaks in February and March across years, suggesting that the spawning season extended from winter to early spring. Early stage eggs (stages 1 and 2) were more frequently found in the coastal waters around the Izu Islands to the Boso area of southeastern Japan, indicating that these regions serve as major spawning grounds. Moreover, the presence of late-stage eggs (stage 3) and early stage larvae off the northeastern coast supports the hypothesis proposed by Kitagawa (<CitationRef CitationID="CR20">1988</CitationRef>; PhD dissertation, Hokkaido University, Sapporo) that eggs and larvae spawned in southern waters are transported northward to Tohoku, northeastern Japan. The estimates of total egg production and total larval production in the waters east of the Izu Islands fluctuated interannually. These findings offer crucial insights into the early life history of <i>P. japonicus</i> and support future efforts to improve stock assessment and sustainable management.</p>

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Distribution of Japanese codling Physiculus japonicus eggs and larvae off the Pacific coast of Japan: where are “donko” in Tohoku born?

  • 期刊论文

  • 发表日期：

    2026年3月5日

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  • Tomohiro Ishikuro,
  • Mikio Watai

摘要

We aimed to clarify the spawning season, spawning grounds, and horizontal distribution patterns of Physiculus japonicus eggs and larvae on the basis of extensive ichthyoplankton surveys conducted along the Pacific coast of Japan from 2020 to 2024. Specimens were identified and classified on the basis of their morphological characteristics. Eggs and larvae were observed from January to April and showed consistent peaks in February and March across years, suggesting that the spawning season extended from winter to early spring. Early stage eggs (stages 1 and 2) were more frequently found in the coastal waters around the Izu Islands to the Boso area of southeastern Japan, indicating that these regions serve as major spawning grounds. Moreover, the presence of late-stage eggs (stage 3) and early stage larvae off the northeastern coast supports the hypothesis proposed by Kitagawa (1988; PhD dissertation, Hokkaido University, Sapporo) that eggs and larvae spawned in southern waters are transported northward to Tohoku, northeastern Japan. The estimates of total egg production and total larval production in the waters east of the Izu Islands fluctuated interannually. These findings offer crucial insights into the early life history of P. japonicus and support future efforts to improve stock assessment and sustainable management.