Are Fish in Hot Water?

1. Are Fish in Hot Water? Presentation to the Climate Impacts Group University of Washington November 9, 2004 John Bartholow USGS Fort Collins Science Center

2. Approximate “temperature-limited” range of trout under “current” conditions (23.8°C) (Bartholow 1989)

3. Approximate “temperature-limited” range of trout under altered conditions (23.8°C + 2.7°C) (Bartholow 1989)

4. Approximate “temperature-limited” range of trout under altered conditions (23.8°C + 5.5°C) (Bartholow 1989)

5. A Presentation in Four-parts • 1. Evidence for warming in the Lower Klamath River • 2. Linkages between temperature change and freshwater fish biology • 3. Simple assessment method (metric) • 4. Complex assessment method that incorporates both flow and temperature in a mechanistic model

6. “Yeah, well. I don’t care what the new regulations say. ‘Catch and release’ is a stupid rule.”

7. Part One • Review measured data and model results for evidence, if any, of basin-wide warming of the lower Klamath River below Iron Gate Dam in the post-impoundment period (WY 1962-2001) Derived from presentation given with Sharon Campbell, USGS

8. Klamath Basin

9. Methods • Use trend detection methodology (Gilbert 1987) to examine: • Historical basin-wide water temperature records • Simulated river temperatures and derived metrics • Historical air temperature and hydrology records

10. Gilbert (1987) Technique • Provides non-parametric estimates of monthly and annual linear trends in time series data • Works by computing median of all possible slopes between data points • Unbiased by non-normal outliers • Relatively insensitive to randomly missing data • Used previously by hydrologists (Fox et al. 1990)

11. Years of temperature gage record ~ 1960-85 30 16 18 13 16 15 17 14 21 22 25

12. Results of Historical Analysis • Estimated basin-wide water temperature trend averaged 0.4°C increase per decade • 10 stations showed positive trends, but • 2 stations had small negative trends, • 3 stations showed no trend at all, and • Only three stations were statistically significant • Overall – Inconclusive! ?

13. Filling the Temperature Record • Used Army Corps of EngineersHEC-5Q water temperature model (part of the SIAM-DSS) for 1962-2001 • Calibrated to historical and newly collected mean daily temperature data • R² = 0.96, p<0.001 • Mean absolute error ~1.8°C (~1°C w/o bias) • No significant trend in model residuals except at mouth of river, i.e., model was unbiased View Movie

14. Estimated Klamath River Trends, 1962-2001 Upstream to Downstream 

15. Example Trend at Iron Gate Dam Site

16. Metrics from DSS (SIAM) • Cumulative degree-days > 15°C • # Weeks > 15°C • # Days > 20°C • Hot season length (# days > 15°C) • # River km < 15°C(all computed annually)

17. Estimated Metric Trends

18. Season Length (days) > 15°C (First day to last day)

19. Stream Heat Flux Sources

20. Historical Hydrology Trends • Annual trend in discharge was small (-33 cfs/decade) relative to typical flow rates (> 1000 cfs) ?

21. Air Temperature Trends * = NS

22. Trends Perhaps Related to PDO (Univ. of Washington/Mantua 2003)

23. But Correlation Was Not Strong (at least not on an annual basis) ?

24. Conclusions • Analysis of spotty and short duration historical water temperature data proved inconclusive • Simulated water temperatures (to fill in the record) revealed increases in biologically significant temperatures and derived metrics for 1962-2001

25. Conclusions (cont.) • Estimated trend in basin-wide water temperatures was about +0.5°C per decade • Trends seem largely unrelated to hydrology, but, • Trends do seem to be related to basin-wide air temperature • and perhaps to the Pacific Decadal Oscillation

26. Consequences • Trend in both magnitude and duration of temperatures directly relevant to freshwater salmonid survival has been increasing

27. Consequences (cont.) • Mean weekly temperature of 23-24° is a useful benchmark for presence/ absence of coho and Chinook (Eaton et al. 1995) • Mainstem Klamath River regularly exceeds mean weekly temperatures of 24°C (regardless of whether one looks at simulated or measured data)

28. Consequences (cont.) • Cooler weather may return to the basin, but • Until it does, discussion on the fate of the salmon will remain heated! ?

31. Part Two • World’s shortest primer on thermal effects governing fish • Though most of my work has been on coldwater salmonid species, the principles apply across most every aquatic obligate species With thanks to Bruce Webb

32. Thermal Effects • Most aquatic organisms are poikilothermic, i.e. have very limited physiological control over their body temperature • Temperature influences almost every process and relationship governing stream & river biota

33. Thermal Effects on Fish Increasing complexity to understand

34. Functional Forms • A simple view of lethal temperature suggests fish are killed when heated above, or cooled below, their tolerance range 1.0- Survival 0.0- Temperature 

35. Fish Funerals

36. But Note: • Lethality is actually much more complex and influenced by many factors (Langford 1990), including: • rate of temperature change • duration of exposure • acclimation (previous thermal history) • organism size or life history stage • physiological state (starvation or other stresses)

37. Functional Forms (cont.) Opt ZNG ZNG 1.0- Growth (or Performance) 0.0- Temperature  ZNG = Zero Net Growth

38. Note this curve’s skew to the right and the relatively precipitous drop from optimum to zero (or negative) growth Important Considerations Opt ZNG ZNG 1.0- Growth 0.0- Temperature 

39. Also, lethal zone still bounds the curve such that some individuals will grow fast, but population as a whole will decline due to thermal & stress-related mortality Important Considerations (cont.) Opt ZNG-p 1.0- Growth 0.0- Temperature 

40. High end of optimum is emerging as the “gold standard” for setting water temperature criteria for fish populations in serious need of restoration (USEPA 2003) Leading to … Criteria Setting Opt 1.0- Growth 0.0- Temperature 

42. Part Three • A simple assessment model (metric) • Example derived from work on the Stanislaus River in California’s Central Valley With peer review colleagues Mike Deas, Chuck Hanson & Chris Myrick

43. Lower Stanislaus River

44. Longitudinal Profiles (1988) (°F)

45. The Problem (simplified) • Deep reservoir releases (followed by surface releases) largely control downstream thermal regime • Water is a scarce resource • Delivered within a legal and institutional framework • But with attention to salmon restoration goals • Search for improved system operation criteria • What thermal attributes should be measured? • How should they be used to “judge” one (simulated) alternative from another?

46. Previous Thermal Criteria • Dueling Criteria • Irrigation District, vs. • California Department of Fish and Game • Based on thermal tolerance per salmon and steelhead life stage (e.g., adult immigration, adult spawning, egg incubation, fry rearing, juvenile rearing, juvenile emigration, smoltification)

47. Previous Thermal Criteria (cont.) • Used two different metrics for each lifestage based on extensive literature: • Daily average • 7-day average of the daily maximum • And applied two different ways • Multi-tier approach (e.g., optimal, suboptimal, acute) • Degree-days

48. But … • Existing assessment failed to distinguish between water management alternatives for the simulation period • I.E., no clear winners regardless of the criteria applied

49. So We Tried … • Refining their tiered approach using optimum temperatures as now defined by USEPA (2003) • And estimating suboptimal temperature criteria as (Tw(optimal)+b) • where safety factor b = 2oC after Coutant (1972)

50. EPA (2003) “Optimum” Criteria