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Growth-related morphology of “Kunimasu” (Oncorhynchus kawamurae: family Salmonidae) from Lake Saiko, Yamanashi Prefecture, Japan


Biological characteristics of “Kunimasu” (Oncorhynchus kawamurae), poorly known even before the species was prematurely believed extinct, have now become apparent following the examination of 59 specimens from Lake Saiko, Yamanashi Prefecture, Japan and comparison with 58 examples of “Himemasu” (kokanee of Oncorhynchus nerka in Japan), also from Lake Saiko. Significant (p < 0.01) differences between Kunimasu and Himemasu from Lake Saiko occurred in counts of anal-fin rays, pectoral-fin rays, gill rakers (no overlap found) and pyloric caeca. Secondary sexual characters related to maturity level were also found in Kunimasu, the body being more compressed in pre-spawning and spawning males and females than in immature and maturing individuals. Furthermore, maturing male Kunimasu and Himemasu also differed in body shape. Body coloration of Kunimasu also differed according to level of maturity, the nuptial coloration in both sexes being olive-green when alive and black when fresh. Dark dots, found in ca. 40 % of Kunimasu individuals examined, were less distinct than in Himemasu. The spawning season of Kunimasu extended through winter and early spring in Lake Saiko, with spawning males and females remaining near the bottom, compared with non-spawning individuals which occupied the upper and middle profundal zones in the daytime.

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We thank Hisashi Miura (Senboku City, Akita Prefecture, Japan) for making available his document concerning the relocation of eyed eggs from Lake Tazawa, M. Tanaka, Katsuyasu Watanabe, Hiroshi Miura, Manabu Miura, K. Takahashi, K. Mitsui, M. Ohashi, S. Sasaki and N. Sakai for their help in collecting specimens, and T. Kikuchi, M. Kita and Y. Komoda for information on Kunimasu in Lake Saiko. We also thank G.S. Hardy for his critical reading of the manuscript. This study was partly supported by the Core Stage Backup Research Fund of Kyoto University and a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (24370036).

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Correspondence to Yoshiaki Kai.

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This article was registered in the Official Register of Zoological Nomenclature (ZooBank) as 8703294E-30A6-4854-8960-F14A11FFCA7A.

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Nakabo, T., Tohkairin, A., Muto, N. et al. Growth-related morphology of “Kunimasu” (Oncorhynchus kawamurae: family Salmonidae) from Lake Saiko, Yamanashi Prefecture, Japan. Ichthyol Res 61, 115–130 (2014).

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  • Oncorhynchus kawamurae
  • Oncorhynchus nerka
  • Life history stages
  • Secondary sexual characters