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

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) Life History and Sex

Male Life History Expression Genetics –H 2 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

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

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

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

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

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

FL: p-value = < Lipid: p-value = n = 88

FL: p-value = < Lipid: p-value = n = 88

Warm Streams Cool Streams

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

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

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

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

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

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

Jason Dunham - USGS, Gordie Reeves - USFS, Marty Fitzpatrick - USGS, Chris Jordan – NOAAJason Dunham - USGS, Gordie Reeves - USFS, Marty Fitzpatrick - USGS, Chris Jordan – NOAA OSU – Justin Mills, Mark Terwilliger, Matt SloatOSU – Justin Mills, Mark Terwilliger, Matt Sloat ODFW – Tim Unterwegner, Jeff Neal, Jim Ruzycki, Chris James, Shelly Miller, Lisa Borgersen, Ryan Couture, Joseph O'NeilODFW – 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 McMillanFIELD 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 SteelheadersFUNDING – NOAA, USGS, North Fork Umpqua Foundation, Oregon Fly Fishers Club, Delson Bridge to the Future Fund, Washington County Flyfishers, McLoughlin Northwest Steelheaders

QUESTIONS?