Matt Sloat and Gordon Reeves Fisheries and Wildlife Management Oregon State University and USFS PNW Research Station, C

1. Influence of changing thermal regimes on steelhead growth and life history expression Matt Sloat and Gordon Reeves Fisheries and Wildlife Management Oregon State University and USFS PNW Research Station, Corvallis, OR

2. Climate change will alter the thermal regimes of aquatic ecosystems How will aquatic organisms with complex life histories respond to these alterations?

3. O. mykiss life cycle J. Tomelleri Boughton et al. J. Tomelleri

4. O. mykiss life histories Males exhibit alternative mating tactics FW resident- mature early at small size Anadromous- delay maturation and mature at large size photos: J. McMillan

5. 90% 1 Probability of early maturity 20% 0 Length-at-age

6. Lipid storage greater in cold streams and growth (i.e., length) greater in warm streams. (Wilcoxon rank sum test, p = 0.02) (Wilcoxon rank sum test, p >0.001) McMillan et al. (2011) Env. Bio. Fish.

7. colder warmer Probability of early maturity Length-at-age (mm) Redrawn from McMillan et al. (2011) Env. Bio. Fish.

9. 1 Colder Warmer Probability of early maturity 0 Length-at-age

10. Study objective: Determine the influence of thermal regimes on energy allocation and life history expression in O. mykiss • Obtained fertilized eggs from a single pair of Clackamas River steelhead from the Clackamas River Hatchery • Incubated at OSU Salmon Disease Lab

11. Overview of experimental design Difference in thermal regimes represents a 2.5°C increase in mean annual water temperature • 2 thermal regimes • 12 replicates per thermal regime • 24 tanks total

12. Overview of experimental design 30 individually marked fish per tank post hoc analysis: sex ratio ~ 1:1 • 30 fish per tank • 24 tanks total • 720 individually marked fish VIE marks identify individual fish

13. Methods • Monthly growth measurements (FL, mass) of individual fish • Life history categorization • Assessment of smolt status April – June 2011 • Assessment of maturity Aug 2011 • Retrace growth trajectories of fish within life history categories • Whole body lipid analysis (forthcoming)

14. Results

15. Male growth trajectories: length * * * 20mm * * * *

16. Male growth trajectories: mass * * 22g * * * * *

17. Smolts Mature males

18. Male life history expression for steelhead offspring reared under different thermal regimes Smolts: 16% * Smolts: 46% * UN: 8% UN: 5% Mature: 76% * Mature: 49% * Cold thermal regime Warm thermal regime

19. Male growth trajectories by life history type: length Cold regime Warm regime * * * * Length (mm) * * Month Month

20. Male growth trajectories by life history type: mass Cold regime Warm regime * * * Mass (g) * * * * * * Month Month

21. Warm regime Cold regime smolt mature smolt mature smolt mature smolt mature

22. Conclusions: • Despite higher rates of somatic growth, fish experiencing warmer • temperatures had lower rates of maturation • Temperature may alter energy allocation in important ways that • are not captured by measuring somatic growth alone • A mechanistic understanding of physiological responses to altered • thermal regimes is needed to forecast effects of climate change

23. Acknowledgments: Funding provided by USFS PNWRS with additional support from USGS FRESC, Corvallis, ORAFS Carl Bond Memorial Scholarship. Thanks to: Jason Dunham, India Sloat, Jill Pridgeon, Haley Ohms, Amy Lindsley, Stephanie Saunders, Matt Stinson, and staff at ODFW Clackamas Hatchery.

24. photo: Becky Sloat