Effect of damming on distribution of rainbow trout in Hokkaido,Japan |
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Authors: | Mideok Han Takehiko Fukushima Michio Fukushima |
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Institution: | (1) Graduate School of Life and Environmental Science, Laboratory of Advanced Research A501, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan;(2) Graduate School of Life and Environmental Science, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan;(3) National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan |
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Abstract: | Rainbow trout introduced into Hokkaido in 1920 have become widely distributed due to extensive release into many reservoirs
and lakes for sport-fishing; their presence often results in reductions of native fish populations. We analyzed and predicted
the relationship between the probability of occurrence of rainbow trout and the proximity of dams (or attributed reservoirs),
using a database of the presence or absence of rainbow trout collected during 1960–2004 in Hokkaido to clarify the spread
patterns of exotic species (e.g., rainbow trout) due to large-scale damming over a long period. Rainbow trout were abundant
in streams within approximately 10 km of dams in recent years, regardless of whether the stream was up- or down-stream from
the dam and after accounting for the effects of other environmental variables (e.g. elevation, population density, and survey
year). A delayed increase in trout occurrence below dams as compared with above dams suggests that the occurrence below dams
may be largely due to escapement of stocked populations and a continuously increasing abundance since 1970. The management
of dams and reservoirs is necessary to prevent further spread of rainbow trout because they can threaten habitats of native
Japanese salmonids through various mechanisms.
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Keywords: | Damming Exotic fish Generalized additive model Hokkaido Rainbow trout |
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