| Autor: |
Omoto, Naotaka, Maebayashi, Mamoru, Hara, Akihiko, Adachi, Shinji, Yamauchi, Kohei |
| Předmět: |
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| Zdroj: |
Environmental Biology of Fishes; Aug2004, Vol. 70 Issue 4, p381-391, 11p |
| Abstrakt: |
We investigated the occurrence and gonadal maturity of wild sturgeons, which are rarely caught off Hokkaido island in Japan. Based on their morphological features, combined with the data on their cell DNA content, 48 sturgeons were classified into three species and one hybrid. These were the kaluga, Huso dauricus; the Japanese (Sakhalin) sturgeon, Acipenser mikadoi (historically, this species has been considered conspecific with the American green sturgeon, A. medirostris); the Amur sturgeon, A. schrenckii; and the kaluga–Amur sturgeon hybrid; with a ratio of 36 : 10 : 1 : 1. All of them were caught in saline waters, rather than in the fresh-water of the river, although some of them were in saline waters in the mouth of the river. Most of them were smaller than adult size; however, early juvenile fish were not detected. Histological analysis of gonadal development revealed early stages of gametogenesis in the majority of the fish of both genders. These results indicate that several sturgeon species are still occurring in the coastal waters of northern Japan, at different stages of gonadal maturity. In contrast, the lack of reports of both mature and early juvenile sturgeon capture in the Hokkaido rivers may suggest that native spawning populations of Japanese sturgeon have become extinct in Japan. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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