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Distribution, Status, and Likely Future Trends of Bull Trout within the Columbia River and Klamath River Basins
Author(s) -
Rieman Bruce E.,
Lee Danny C.,
Thurow Russell F.
Publication year - 1997
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1997)017<1111:dsalft>2.3.co;2
Subject(s) - trout , habitat , range (aeronautics) , geography , drainage basin , species distribution , habitat fragmentation , ecology , habitat destruction , fragmentation (computing) , distribution (mathematics) , climate change , fishery , biology , fish <actinopterygii> , mathematical analysis , materials science , cartography , mathematics , composite material
We summarized existing knowledge regarding the distribution and status of bull trout Salvelinus confluentus across 4,462 subwatersheds of the interior Columbia River basin in Oregon, Washington, Idaho, Montana, and Nevada and of the Klamath River basin in Oregon, a region that represents about 20% of the species' global range. We used classification trees and the patterns of association between known distributions and landscape characteristics to predict the likely distribution of bull trout in unsampled subwatersheds. Bull trout are more likely to occur and the populations are more likely to be strong in colder, higher‐elevation, low‐ to mid‐order watersheds with lower road densities. Our results show that bull trout remain widely distributed and occur in most of the subbasins representing the potential range. Some strong and relatively secure populations exist. In general, bull trout are better represented in the region as a whole than many other native species. Important declines in distribution and status are evident, although the extent of change is clouded by uncertainties in the historical distribution. Despite the broad distribution, much of the current range is poorly represented by strong or protected populations. The southern margins of the range are a particular concern and could be an important priority for conservation management. Continued habitat loss associated with disruptive land use practices threatens remaining bull trout populations. Even with no further habitat loss, existing fragmentation could contribute to continuing local extinctions aggravated by the expansion of introduced species and the effects of climate change.