Habitat niche separation of the nonnative rainbow trout and native masu salmon in the Atsuta River,Hokkaido, Japan |
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Authors: | Koh Hasegawa Toshiaki Yamamoto Shigeru Kitanishi |
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Institution: | (1) National Salmon Resources Center, Fisheries Research Agency, Nakanoshima, Toyohira, Sapporo Hokkaido, 062-0922, Japan;(2) Department of Veterinary Nursing and Technology, Nippon Veterinary and Life Science University, Musashino, Tokyo 180-8602, Japan;(3) Graduate School of Environmental Earth Science, Hokkaido University, Sapporo Hokkaido, 060-0810, Japan |
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Abstract: | The mechanisms by which nonnative species establish populations can be classified into two broad categories: they usurp the
niches of native species through interspecific competition, or they avoid this intense interspecific competition by making
use of minimal niche overlap with the native species. In this study, we considered how a nonnative salmonid species, the rainbow
trout Oncorhynchus mykiss, established a population in the presence of the native salmonid species, the masu salmon O. masou, in Hokkaido, Japan. Circumstantial field evidence shows that the masu salmon exceeds the rainbow trout in abundance and
suggests that these species use different types of cover habitat (rainbow trout abundance increases with increasing abundance
of large woody debris aggregates, whereas masu salmon abundance increases with increasing abundance of undercut banks). These
results imply that the rainbow trout established a population due to minimal niche overlap with the masu salmon, and not by
competitive exclusion of the native species. |
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