Cold Tolerant Fish in Alpine Streams

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

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

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

4. 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

5. Alfredson et al, 2007

6. 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

7. 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 • Become nocturnal in winter

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

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

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

11. Conclusion • Fish adapt to extreme winter temperatures by • Increase in energy stores • Lower metabolism • Nocturnal • 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.

12. Literature Cited • Alfredsen, Knut, Larry Greenberg, Ari Huusko, Saija Koljonen,Tommi Linnansaari, Pauliina Louhi, Mari Nykanen, Morten Stickler and Teppo Vehanen. 2007. The Ice Lane: the winter ecology of stream salmonids, River Research and Applications 23-5: 469-91. • Burkhardt-holm, Paricia, R.E. Hari, Herbert Guttinger, David M Livingston and Rosi Siber. 2006. Consequences of climatic change for water temperature and brown trout populations in Alpine rivers and streams, Global Change Biology 12: 10-26. • Coleman, M. A. and K.D. Faushc. 2007. 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: 639-54. • Ward, JV. Ecology of Alpine Streams, EAWAG News 54: 3-5