Maturity of Laemonema longipes in the Pacific area off eastern Hokkaido [Japan]
1997
Hamatsu, T. (Hokkaido National Fisheries Research Inst., Yoichi (Japan)) | Yabuki, K.
To clarify the reproductive character of Laemonema longipes, gonadal maturity was examined in fish caught by commercial boats in the Pacific area off eastern Hokkaido, from April 1994 to september 1996. No individuals that were spawning or were just before spawning were found in sampled fish, suggesting the absence of a spawning area of this species off eastern Hokkaido. Gonado-somatic index (GSI) of adult fish gradually increased from september to January in both sexes, however, the measured oocyte diameters (0.5mm) of the most developed ovaries were considerably smaller than the value of fully grown vitellogenic oocytes (0.7mm) in a previous report of Yokota and Kawasaki (1990). The monthly catch was large in autumn and spring off eastern Hokkaido. The rate of maturing fish in the catch was over 50% in September and decreased to 10-20% in November to January. Judging from these results, in addition to some previous reports, we propose a tentative scheme of spawning migration of adult Laemonema longipes between eastern Hokkaido and the spawning area near Kanto. The minimum body lengths of primary maturation were 410mm in females and 358mm in males, respectively. Half of the female individuals matured at about 500mm in body length, and all female individuals matured at about 550mm in body length
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