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Partial migration in Oncorhynchus mykiss : A spatially and sexually explicit approach

Partial migration in Oncorhynchus mykiss : A spatially and sexually explicit approach. J. McMillan photos. Justin Mills, USGS/OSU (MS, 2008) Jason Dunham, USGS-FRESC Chris Jordan, NOAA-Fisheries Gordie Reeves, USFS-PNW John McMillan, USGS/OSU (MS 2009) Chris Zimmerman, USGS.

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Partial migration in Oncorhynchus mykiss : A spatially and sexually explicit approach

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  1. Partial migration in Oncorhynchus mykiss: A spatially and sexually explicit approach J. McMillan photos Justin Mills, USGS/OSU (MS, 2008) Jason Dunham, USGS-FRESC Chris Jordan, NOAA-Fisheries Gordie Reeves, USFS-PNW John McMillan, USGS/OSU (MS 2009) Chris Zimmerman, USGS

  2. Sex and migration J. McMillan photos

  3. Space: John Day River

  4. Study objectives • Broad-scale measures of female anadromy • Predict patterns of female anadromy • Assess potential importance of local variability

  5. Study design Collect juvenile O. mykiss Test for non-random distribution Determine maternal origin Collect water samples Sites with anadromy Tests of model performance Broad-scale environmental variable(s) Predictive model Test for residual spatial variation

  6. 2.4 2.2 2 1.8 Sr/Ca ratio 1.6 1.4 1.2 1 0 200 400 600 Distance from centrum (microns) Collection and maternal origin Four otoliths Two fish + water sample P. Stratis photos

  7. Anadromy was common, widespread Anadromy at 52 of 72 sites Two rainbow trout offspring One of each Two steelhead offspring

  8. R S = Rainbow trout offspring = Steelhead offspring How is maternal origin distributed? S R R R R S S S R S S R R R S R R R S R S S S S S S S S R S S S R S S S S S R S S R R S Random distribution Numerical dominance or spatial segregation

  9. Maternal origin was clustered ² = 11.15, df = 1, P < 0.001 n = 47 sites; only those with 2 juveniles < 2 years old

  10. Objective 2: Predictive model Sites with anadromy Tests of model performance Broad-scale environmental variable(s) Predictive model Test for residual spatial variation

  11. Stream size and anadromy • Associated with many ecological and physical processes • Sediment transport • Water temperature • Biological organization • Readily used in spatial statistics • Simple to estimate for large area

  12. 2000 1500 1000 Elevation (m) 500 0 -5 -4 -3 -2 -1 0 1 2 Log(mean annual runoff; m3/s) Rainbow trout offspring Steelhead offspring Anadromy varied with stream size

  13. Autocorrelated residuals A B ΔResidual ΔDistance Mantel test for spatial autocorrelation Euclidean distance Stream network distance

  14. 1.0 0.8 0.6 ΔResiduals 0.4 0.2 0.0 0 100 200 300 400 500 600 ΔStream network distance (km) No spatial autocorrelation • Mantel tests non-significant • Spatial gradients accounted for by model Subset of 1/5 of pairwise distances

  15. Bottom lines • Sampling approach proved useful • Female anadromy was predictable • Stream size accounted for most of the broad-scale variability in female anadromy • Local factors potentially source of remaining variability J. McMillan photos

  16. Improvements • Model improvements • Redd counts • Combined probabilistic predictions • Local factors • Bioenergetics • Species interactions • Community effects • Ecosystem processes • Doesn’t address males • Doesn’t address resident females

  17. Discussion • The process: critical periods, sexual tension, and everything in-between • The evidence: observation, model, experiment – correlation vs causation? • The relevance: ESA listing, modeling, monitoring, recovery du les sauvages?

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