Oncorhynchusにおける主要生態の分化について
During the past 70 or 80 years, salmon have been introduced to the southern hemisphere with a view to acclimatising them as sea-run forms. Acclimatisation has proved successful so far only for the king salmon in the South Island of New Zealand. In spite of this limited success the acclimatisation at...
| Main Authors: | , , , , , |
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| Format: | Report |
| Language: | Japanese |
| Published: |
近畿大学農学部
1980
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| Subjects: | |
| Online Access: | https://kindai.repo.nii.ac.jp/?action=repository_uri&item_id=5089 http://id.nii.ac.jp/1391/00005083/ |
| Summary: | During the past 70 or 80 years, salmon have been introduced to the southern hemisphere with a view to acclimatising them as sea-run forms. Acclimatisation has proved successful so far only for the king salmon in the South Island of New Zealand. In spite of this limited success the acclimatisation attempt has continued to this day. For example, a large number of Oncorhynchus keta have been introduced into the west coast waters of Chile every year since 1973, with no avail.We have begun investigations into the causes of successful establishment of the king salmon in New Zealand and earlier reported on the oceanographic conditions considered necessary for the acclimatisation. In the present study we report on the actual conditions of ecological differentiation among several species of salmon belonging to the genus Oncorhynchus; in particular, their distribution and origin, the body size attained by various species at the commencement of their seaward migration, the magnitude of their migration in the sea, the stage of their gonadal development at the end of their oceanic life, the survival rate of adults after their first reproduction, and the presence or absence of land-locked forms.Information collected on the above ecological attributes indicate that the degree of ecological differentiation has increased in the following order: Amago Salmon, O. rhodurus, endemic to Japan → Cherry Salmon, O. masou, endemic to the Far East → King Salmon, O. tschawytscha, → Silver Salmon, O. kisutch, → Red Salmon O. nerka group ~ Chum SalmonO. keta → Pink Salmon, O. gorbuscha. |
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