Reproductive failure of Chinook salmon: Effects of limited behavioral plasticity in warming rivers
Monitoring of populations near the margins of a species’ natural distribution, which often occur in habitats approaching their thermal limits and may be susceptible to even modest temperature increases, can provide insights on the effects of climate stressors expected to affect more northerly populations in the future. Annual monitoring activities track the escapement, document spatial and temporal spawning distribution and estimate juvenile production and outmigration characteristics of fall-run Chinook salmon, Oncorhynchus tshawytscha, in California’s Stanislaus River. Monitoring during the recent record-breaking drought revealed only minor migration- and spawning delays for returning adults, despite water temperature conditions considered detrimental to egg incubation. Results from degree-day analyses to estimate fertilization dates of emigrating juvenile salmon suggests diminished reproductive success of early spawners. While peak timing of reproduction might shift over time resulting from poor fitness of early spawners, this reduces in-river rearing opportunities of juveniles, which must emigrate before thermal connectivity to the marine environment is lost in spring. Long-term air temperature data indicates that cooling below certain temperature thresholds occurs progressively later in fall, while the same thresholds are exceeded earlier in spring, reducing the window for emigration of juvenile fall-run Chinook salmon and, by extension, further diminishing population resilience
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Reproductive failure of Chinook salmon: Effects of limited behavioral plasticity in warming rivers
- 1. AFS / TWS 2019 Reno, Nevada Hellmair, M., T.J. Pilger, M.L. Peterson, D. Demko, & A.N. Fuller Reproductive failure of Chinook salmon: effects of limited behavioral plasticity in warming rivers
- 2. Introduction and Background www.FISHBIO.com • Stanislaus River • Tributary to San Joaquin River • Nearly 100 km below barrier • Southern boundary of distribution • Intensively monitored system • Adult upstream migration • Spawning surveys • Juvenile Outmigration • Complementary studies • Discharge and water temperature
- 3. www.FISHBIO.com Goodwin Dam (°C) RST Weir Knights Ferry (°C)
- 4. Methods: Adult Return Timing Resistance board weir downstream of spawning grounds* • Annually since 2003 • Automated infrared and video monitoring 24/7 • Used to calculate passage percentiles www.FISHBIO.com * Peterson et al. 2017. Environmental Factors […] . NAJFM 37: 78-93.
- 5. Methods: Reproductive Timing Redd surveys throughout spawning reach*: • Biweekly throughout the spawning period • Counts and location of new redds • Superimposition www.FISHBIO.com *Peterson et al. 2019. Stability in reproductive timing […]. Fisheries Management and Ecology, in press.
- 6. Methods: Juvenile Production and Outmigration Timing RST sampling downstream of spawning grounds*: • Operated annually throughout the outmigration period • All catch counted, subsample measured • Mark-recapture efficiency releases www.FISHBIO.com *Pilger et al. 2017. Evaluation of Long-Term Mark-Recapture Data […]. SFEWS 17(1).
- 14. Juvenile Production • Focus on fry (<35 mm FL) • Assumed recently emerged (within days) • Evaluate predicted vs. observed timing www.FISHBIO.com
- 18. Summary • Adults arrive AND spawn without great delay despite unsuitable temperatures. • High incubation mortality, reduced production. • Phenological shift due to directional selection and heritability of migration and reproductive timing? Unlikely! • Window of thermal suitability for outmigration is shrinking! • Implications beyond the Stanislaus River. www.FISHBIO.com
- 19. Implications, cont. www.FISHBIO.com Figure modified from Herbold et al. 2018. SFEI 16:2. • Juveniles of all runs migrate through San Francisco estuary • Lower river temperature cannot be regulated • Increasing air temperatures warm water temperatures
- 22. Conclusions www.FISHBIO.com • Shift in phenology limited by shrinking window of thermal suitability • Short term: management of coldwater storage • Long term: range contraction?
- 23. Acknowledgements Funding provided by: Oakdale and South San Joaquin Irrigation Districts We thank the following people for their efforts, support, and advice: FISHBIO – Shaara Ainsley, Patrick Cuthbert, Jeremy Pombo, John Montgomery, Jim Inman, Chrissy Sonke, Mike Kersten, Tara Lamb, Garth Jaehnig, Rob Fuller, Earl Fuller, Logan Douglas, Scott Stocker, Rick Biedenweg, Graham Buggs, Ian Herzberger, Ben Griffith, Steve Clark, Dee Thao, Erin Loury, Bryce Neal, and Garret Muniain www.FISHBIO.com
- 24. FISHBIO Oakdale, California Chico, California Santa Cruz, California FISHBIO Laos Vientiane Capital, Lao PDR FISHBIO CR Boca del Rio Sierpe Costa Rica Questions? Michael Hellmair michaelhellmair@fishbio.com 530.892.9686 www.FISHBIO.com