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Early male maturity in O. mykiss : influences of condition and temperature

Early male maturity in O. mykiss : influences of condition and temperature. John McMillan NOAA/NWFSC J. Dunham, M. Fitzpatrick G. Reeves, C. Jordan. Life History and Sex. Females Reproductive fitness closely tied to size Males Size less important because of mating tactics.

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Early male maturity in O. mykiss : influences of condition and temperature

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  1. Early male maturity in O. mykiss: influences of condition and temperature John McMillan NOAA/NWFSC J. Dunham, M. Fitzpatrick G. Reeves, C. Jordan

  2. Life History and Sex • Females • Reproductive fitness closely tied to size • Males • Size less important because of mating tactics Anadromous- large males (fighters, mimics, sneakers) Resident- small males (sneakers, group)

  3. Male Life History Expression • Genetics • H2 for growth to age-1 = 0 – 0.3 • Reviewed by Hendry and Stearns 2004 • Environment • Temperature (e.g., extent of growing season) • Individual condition • Growth and lipids • Early maturity  lipid, growth

  4. O. mykiss • Anadromous- resident males • Distributed across varying environments • Science • Mating behavior • Reproductive contributions • Life history expression?

  5. Age-1+ resident male maturity • Is probability of maturity positively associated with size and lipids? 2. Do size and lipids differ between streams w/contrasting growing seasons?

  6. Age-1+ resident male maturity • Is probability of maturity positively associated with size and lipids? 2. Do size and lipids differ between streams w/contrasting growing seasons?

  7. John Day River • O. mykiss • Observations of small resident males • Diverse landscape • Survey sites and sampling • 30 Sites: ~ 100 m in length, ODFW-EMAP • July – September 2007 • 3 – 12 fish/site in age-1+ size range

  8. Methods • Sex/maturity • Dissection & microscopy • Age • Otoliths and scales • Condition • Growth rate: Fork length (mm) at age-1+ • Whole body lipid content: chemical lipid extraction • Temperature • Thermographs: Sept. 11,2007 – August 11, 2008

  9. FL: p-value = < 0.0001 Lipid: p-value = 0.0036 n = 88

  10. FL: p-value = < 0.0001 Lipid: p-value = 0.0036 n = 88

  11. Warm Streams Cool Streams

  12. F M Males & Females 150 n = 80 n = 88 130 • No difference in length 110 - Wilcoxon Rank-Sum - p-value = 0.37 90 Fork Length (mm) 10% • No difference in lipids - Wilcoxon Rank-Sum - p-value = 0.54 5% Lipid Content 0%

  13. Warmer = longer FL Age 1+ n = 55 n = 68 Wilcoxon Rank-Sum: p-value = 0.03

  14. Cooler = higher lipids (%) Wilcoxon Rank-Sum: p-value = < 0.001

  15. Conclusions • Increased size, lipid = more likely mature • Consistent with most research on fish in captivity and wild • Lipids and length did not covary! • Differs: brook charr and brown trout • Greater length = anadromy • Those studies did not measure lipid content

  16. Temperature • Longer in warmer streams • Supported by Tattam (2006) • Other explanations • Maternal effect • Emergence timing and prior residence • Higher lipids in cooler streams • Consistent with other species of fish • John Day similarities (Feldhaus 2006) • Suggests a general pattern

  17. Implications • Evolution • Proximate influences • Ultimate consequences • Ecology • Evolution x environment • Management • Varying sex ratios in smolts?

  18. Jason Dunham - USGS, Gordie Reeves - USFS, Marty Fitzpatrick - USGS, Chris Jordan – NOAA • OSU – Justin Mills, Mark Terwilliger, Matt Sloat • ODFW – Tim Unterwegner, Jeff Neal, Jim Ruzycki, Chris James, Shelly Miller, Lisa Borgersen, Ryan Couture, Joseph O'Neil • FIELD WORK – Nick Weber, Jeremiah Leslie, Ian Tattam, Bill McMillan • FUNDING – NOAA, USGS, North Fork Umpqua Foundation, Oregon Fly Fishers Club, Delson Bridge to the Future Fund, Washington County Flyfishers, McLoughlin Northwest Steelheaders

  19. QUESTIONS?

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