Review of relative fitness (RF) of hatchery- and natural-origin salmon and steelhead

Review of relative fitness (RF) of hatchery- and natural-origin salmon and steelhead
Barry Berejikian NOAA Fisheries Northwest Fisheries Science Center Resource Enhancement and Utilization Technologies Division Manchester Research Station

Previous reviews

Berejikian, B.A., and M.J. Ford. 2004. Review of relative fitness of hatchery and natural salmon. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-61, 28 p
Araki, H., B. A. Berejikian, M. J. Ford, and M. S. Blouin. 2008. Fitness of hatchery-reared salmonids in the wild. Evolutionary Applications 1:342-355.

Provide an overview of RF from published and on-going studies
Focus in on effects in supplementation programs
Identify some important variables that may influence the outcome of RF studies
Recommendations regarding future RF studies

Relative fitness: (R/Sh) /(R/Sw)
Hatchery fish: born in the hatchery
Wild or natural-origin fish: born in the natural environment
Hatchery generations: number of generations the hatchery had been operating

Potential causes of differential fitness of hatchery and wild salmon

Environmental: Incubation and juvenile rearing environment
- age-at-maturity
- spawn timing
- size-at-age
- spawning location
Genetic
- Domestication selection (adaptation to the hatchery)
- Intentional artificial selection
- Other genetic mechanisms (inbreeding, founder effects, etc)

Re-visiting Araki et al. 2007: The Hood River Study

Revisiting Araki et al. 2007

Locally-derived hatchery broodstocks

Supplementation programs

Density-dependent relative breeding success

Hatchery male coho salmon competitively inferior to wild males
Hatchery females spawned later, but suffered higher levels of nest superimposition
Relative breeding success lower at higher density

Density dependent relative breeding success

Male Atlantic salmon competitively inferior to wild males
1st generation hatchery fish (Cww vs Www)
Relative breeding success lower at higher density

Gender effects?

- Non-local stocks perform poorly
- Single generation effects on RF appear to be fairly small (except for Araki et al. 2007, 2009)
- Very little data on lifetime RF
- Varying intensity of competition may influence relative breeding success
- Gender effects are inconsistent
- Future studies should focus on genetic fitness (e.g., Schroder et al. in the Yakima R)

Supplementation programs