Effects of hydrologic change and variability on upstream limits of stream fish distribution

Project Leader: 
Research Partners: 
Benjamin Letcher, Andrew Whiteley
Project Fellows: 
Science Themes: 

Coldwater stream fishes are widely predicted to move upstream in response to warming downstream river temperatures.  However, in the process they may encounter upstream limits, which are likely to be exacerbated by increased hydrologic variability if upstream locations draining small basins switch from perennial to ephemeral flow, with important but currently unknown implications for coldwater habitat and stream fish populations.  In this project, we will look at the current determinants of upstream limitation for Eastern Brook Trout in several (8-10 large watersheds) throughout their native range, and use hydrologic models and GIS analysis to predict future upstream limits and consequent habitat distributions under climate change scenarios.

We have identified key climate-associated drivers of brook trout occupancy, abundance and population dynamics. High summer temperatures appear to decrease brook trout growth and survival across a wide range of environmental contexts, and factors associated with relatively low summer water temperatures (including high levels of forest cover) increase probability of occupancy. In contrast, the relationship between streamflow, population dynamics, and occupancy was more context-dependent requiring additional research to establish robust relationships and forecasts. Across five watersheds in the northeast, we have so far found little evidence of reduced occupancy or abundance in small (< 1 km2) watersheds, suggesting that these very small headwaters could serve as vital refugia in a changing climate.

This project provides a framework for managers to predict status of coldwater fisheries resources and differences in relative resilience among streams, watersheds and regions.


·  Myers BJE, Dolloff CA, Webster JR, Nislow KH, Fair B, Rypel AL. Fish assemblage production estimates in Appalachian streams across a latitudinal and temperature gradient. Ecol Freshw Fish. 2018;27:363–377. https://doi.org/10.1111/eff.12352

·  Robinson, Zachary L., Coombs, Jason A., Hudy, Mark.,  Nislow, Keith H., Letcher, Benjamin H., Whiteley, Andrew R. 2017 . Experimental test of genetic rescue in isolated populations of brook trout. Molecular Ecology. 26:4418–4433.  

·  Dethier, Evan, Magilligan Francis J., Renshaw Carl E., and Nislow Keith H, 2016, The role of chronic and episodic disturbances on channel-hillslope coupling: the persistence and legacy of extreme floods. Earth Surface Processes and Landforms 

·  Kanno, Y., Letcher, B.H., O'Neil, K.P., Nislow, K. 2015. Environmental factors affecting brook trout occurence in small headwater stream sections. KTransactions of the American Fisheries Society: 372-382.

·  Bassar, R. D., Letcher, B. H., Nislow, K. H. and Whiteley, A. R. 2015. Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout. Glob Change Biol. 22(2): 577-593.

·  Daniels, Amy, Nancy Shaw, Dave Peterson, Keith Nislow, Monica Tomosy, and Mary Rowland. 2014. Facing Climate Change in Forests and Fields. The Wildlife Professional. 

·  Letcher, Benjamin H., Schueller Paul, Bassar Ronald D., Nislow Keith H., Coombs Jason A., Sakrejda Krzysztof, Morrissey Michael, Sigourney Douglas B., Whiteley Andrew R., O'Donnell Matthew J., et al. 2014. Robust estimates of environmental effects on population vital rates: an integrated capture-recapture model of seasonal brook trout growth, survival and movement in a stream network. Journal of Animal Ecology, 11/2014.

  • Brook trout population dynamics: Integrated modeling across scales and data types. Presented, American Fisheries Society Annual Meeting, Aug 17 2014 Quebec City, Ben Letcher, Keith Nislow et al.

  • Science-management partnerships for brook trout conservation in the context of climate change.  USDA Forest Service Partnership Office Webinar Series 2/12/2015.

  • Forests, landscapes, and fishes in a changing regional environment. Northern States Research Cooperative Webinar Series. April 30, 2015

  • Climate-mediated portfolio effects for headwater resident trout. Annual Meeting of the American Fisheries Society of America, Portland, OR. August 16-20 2015. Keith Nislow.

  • Management of populations and habitats int he contesxt of climate-driven changes in disturbance regimes. University of Connecticut Seminar Series, October 30th 2015.