Cold Tolerant Fish in Alpine Streams Lauren Pacheco Winter Ecology Spring 2008 Mountain Research Station, University of Colorado, Boulder

Different Alpine Streams  Kryal Fed by glacial melt water Fed by glacial melt water  Krenal Originate from alluvial springs and hill slope springs Originate from alluvial springs and hill slope springs  Rhithral Originate as outlet stream of lake or fed by snow melt runoff Originate as outlet stream of lake or fed by snow melt runoff

Where Cold Tolerant Fish Live  According to Flemming Kryal rivers are better quality overwintering environment than rhithral systems Kryal rivers are better quality overwintering environment than rhithral systems During winter have higher winter dischargeDuring winter have higher winter discharge Increases juvenile salmonids survivalIncreases juvenile salmonids survival Glacier melt rivers and lake system combination Glacier melt rivers and lake system combination Greater salmon population in cold regionsGreater salmon population in cold regions Lakes connected to kryal rivers have high spawning flowsLakes connected to kryal rivers have high spawning flows Reduce high turbidity and trap sedimentReduce high turbidity and trap sediment

How are Fish Adapted to Winter?  Migrate down stream to warmer conditions  Produce “anti-freeze”, sodium chloride in the fluids of the body  Stay in alpine streams and lakes

Alfredson et al, 2007

Why do Fish Stay in Alpine Streams  Sensitive to warm water  Salmon and trout spawn in cold winter streams and lakes after temperatures drop below 4˚C in in fall and eggs don’t hatch until later winter – early spring

How do they adapt?  Stay in lakes  Lower metabolism  Build up fat reserves  Find winter habitat with high shelter 18-25% greater survival rate in rivers with more complex bank habitats 18-25% greater survival rate in rivers with more complex bank habitats  Become nocturnal in winter

Winter Mortality and Winterkill  Winter mortality of alpine fish due to Starvation Starvation Predation Predation Thermal Stress Thermal Stress  Winterkill Mass mortality events (Hurst) Mass mortality events (Hurst) Survival rates of 62% to 10% Survival rates of 62% to 10%

Global Warming  Water temperatures increasing  Brown trout lose 7.5 % of total habitat with an increase of 1˚C in air temperature

Future Research?  More research on how fish overwinter in alpine streams  Increase in observation of habitat as climate temperatures change.

Conclusion  Fish adapt to extreme winter temperatures by Increase in energy stores Increase in energy stores Lower metabolism Lower metabolism Nocturnal Nocturnal Finding habitat with shelter Finding habitat with shelter  Every year fish spawn thousands of eggs to offset the population decrease due to winter mortality.  Like many alpine animals, fish including trout and salmon may be at risk at shrinking habitat.

Literature Cited   Alfredsen, Knut, Larry Greenberg, Ari Huusko, Saija Koljonen,Tommi Linnansaari, Pauliina Louhi, Mari Nykanen, Morten Stickler and Teppo Vehanen The Ice Lane: the winter ecology of stream salmonids, River Research and Applications 23-5:  Burkhardt-holm, Paricia, R.E. Hari, Herbert Guttinger, David M Livingston and Rosi Siber Consequences of climatic change for water temperature and brown trout populations in Alpine rivers and streams, Global Change Biology 12:  Coleman, M. A. and K.D. Faushc Cold summer temperature regimes cause a recruitment bottleneck in age-0 Colorado River cutthroat trout reared in laboratory streams, Transactions of the American Fisheries Society 136:  Ward, JV. Ecology of Alpine Streams, EAWAG News 54: 3-5