Reconnecting a Fragmented River: Movements of Westslope Cutthroat Trout and Bull Trout after Transport Upstream of Milltown Dam, Montana

Climate warming is expected to have substantial impacts on native trout across the Rocky Mountains, but there is little understanding of how these changes affect future distributions of co-occurring native fishes within population strongholds. We used mixed-effects logistic regression to investigate the role of abiotic (e.g., temperature) and biotic factors (Bull Trout presence, Salvelinus confluentus) on distributions of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi; WCT) in the North Fork Flathead River, USA and Canada. The probability of WCT presence increased with stream temperature and decreased with channel gradient and Bull Trout presence, yet the effect of Bull Trout was reduced with increasing pool densities. Combining this model with spatially-explicit stream temperature projections, we predict a 29% increase in suitable habitat under high emissions through 2075, with gains at mid-elevation sites predicted to exceed Bull Trout thermal tolerances and high-elevation sites expected to become more thermally suitable for WCT. Our study illustrates the importance of considering abiotic and biotic drivers to assess species response to climate change, helping to guide local scale climate adaptation and management.

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Potential future climate effects on mountain hydrology, stream temperature, and native salmonid life history

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2013-0221 ◽

2014 ◽

Vol 71 (2) ◽

pp. 189-202 ◽

Cited By ~ 16

Author(s):

Ryan J. MacDonald ◽

Sarah Boon ◽

James M. Byrne ◽

Mike D. Robinson ◽

Joseph B. Rasmussen

Keyword(s):

Cutthroat Trout ◽

Stream Temperature ◽

Climate Impacts ◽

Future Climate ◽

Bull Trout ◽

Westslope Cutthroat Trout ◽

Environmental Pressures ◽

Oncorhynchus Clarkii ◽

Thermal Regimes ◽

Native Salmonids

Native salmonids of western North America are subject to many environmental pressures, most notably the effects of introduced species and environmental degradation. To better understand how native salmonids on the eastern slopes of the Canadian Rocky Mountains may respond to future changes in climate, we applied a process-based approach to hydrologic and stream temperature modelling. This study demonstrates that stream thermal regimes in western Alberta, Canada, may only warm during the summer period, while colder thermal regimes during spring, fall, and winter could result from response to earlier onset of spring freshet. Model results of future climate impacts on hydrology and stream temperature are corroborated by an intercatchment comparison of stream temperature, air temperature, and hydrological conditions. Earlier fry emergence as a result of altered hydrological and thermal regimes may favour native westslope cutthroat trout (Oncorhynchus clarkii lewisii) in isolated headwater streams. Colder winter stream temperatures could result in longer incubation periods for native bull trout (Salvelinus confluentus) and limit threatened westslope cutthroat trout habitat.

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Genetic Inventory of Bull Trout and Westslope Cutthroat Trout in the Pend Oreille Subbasin, 2002-2003 Annual Report.

10.2172/889868 ◽

2003 ◽

Author(s):

Joseph R. Maroney ◽

James B. Shaklee ◽

Sewall F. Young

Keyword(s):

Annual Report ◽

Cutthroat Trout ◽

Bull Trout ◽

Westslope Cutthroat Trout

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Length Variation in Age-0 Westslope Cutthroat Trout at Multiple Spatial Scales

North American Journal of Fisheries Management ◽

10.1577/m07-120.1 ◽

2008 ◽

Vol 28 (5) ◽

pp. 1529-1540 ◽

Cited By ~ 5

Author(s):

Kathleen E. McGrath ◽

J. Michael Scott ◽

Bruce E. Rieman

Keyword(s):

Spatial Scales ◽

Cutthroat Trout ◽

Length Variation ◽

Westslope Cutthroat Trout ◽

Multiple Spatial Scales

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Metabolic performance and thermal preference of Westslope Cutthroat Trout Oncorhynchus clarkii lewisi and non-native trout across an ecologically relevant range of temperatures

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2020-0173 ◽

2021 ◽

Author(s):

Camille J. Macnaughton ◽

Travis C. Durhack ◽

Neil J. Mochnacz ◽

Eva C. Enders

Keyword(s):

Brook Trout ◽

Cold Water ◽

Cutthroat Trout ◽

Intermittent Flow ◽

Performance Curve ◽

Westslope Cutthroat Trout ◽

Oncorhynchus Clarkii ◽

Thermal Niche ◽

Preferred Temperatures ◽

Metabolic Performance

The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature gradients and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) at 5, 10, 15, 20, and 22°C and compared temperature preference (Tpref) of the species to non-native Brook Trout, Brown Trout, and Rainbow Trout. Intermittent-flow respirometry experiments demonstrated that metabolic performance of Westslope Cutthroat Trout was optimal at ~15 °C and decreased substantially beyond this temperature, until lethal temperatures at ~25 °C. Adjusted preferred temperatures across species (Tpref) were comparatively high, ranging from 17.8-19.9 °C, with the highest Tpref observed for Westslope Cutthroat Trout. Results suggest that although Westslope Cutthroat Trout is considered a cold-water species, they do not prefer or perform as well in cold water (≤ 10°C), thus, can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species‐specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for Westslope Cutthroat Trout.

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