Flexible seaward migration of Dolly Varden Salvelinus malma in the Shiretoko Peninsula,Hokkaido, Japan |
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| Authors: | Yoshiyuki Umatani Takaomi Arai Koji Maekawa |
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| Affiliation: | 1.Field Science Center for Northern Biosphere,Hokkaido University,Sapporo,Japan;2.International Coastal Research Center, Ocean Research Institute,University of Tokyo,Otsuchi,Japan;3.Nakagawa Experimental Forest, Forest Research Station, Field Science Center for Northern Biosphere,Hokkaido University,Otoineppu,Japan;4.Environmental and Life Sciences Programme, Faculty of Science,Universiti Brunei Darussalam,Gadong,Brunei Darussalam |
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| Abstract: | The migratory history of Dolly Varden Salvelinus malma was investigated in 30 streams in the Shiretoko Peninsula, Hokkaido, Japan, which is in the southern part of their distribution. Captured Dolly Varden were classified into two categories by their body coloration: silvery fish were thought to be an anadromous form, and non-silvery fish a fluvial form that remains in freshwater throughout its life. Forty-seven of 1,739 Dolly Varden collected in the spring and ten of 2,126 Dolly Varden collected in the autumn were silvery fish. Twenty silvery fish and 120 non-silvery fish were examined by analysis of otolith Sr:Ca ratio. Three silvery fish from autumn and 15 non-silvery fish had migrated to salt water or brackish water. The other specimens of silvery fish were regarded as smolt or pre-smolt before seaward migration. The present study suggests that Dolly Varden in the Shiretoko Peninsula have a flexible migratory history, where some of the non-silvery fish utilize marine environments while some individuals follow an anadromous life history. |
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