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Evaluation of Hydraulic Redd Sampling for Salmon and Steelhead Conservation Hatchery Programs

This study evaluates the effectiveness of hydraulic redd sampling (HRS) as a tool for salmon and steelhead conservation hatchery programs. It compares HRS with artificial spawning and assesses embryo mortality caused by HRS. The study also estimates the effective population size in a captive rearing program that uses HRS and discusses the pros and cons of HRS in achieving the changing goals of salmon and steelhead hatcheries.

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Evaluation of Hydraulic Redd Sampling for Salmon and Steelhead Conservation Hatchery Programs

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  1. Evaluation of hydraulic redd sampling as a tool for salmon and steelhead conservation hatchery programs Barry Berejikian1, Dmitri Vidergar2, Josh Gable3 1NOAA Fisheries, Northwest Fisheries Science Center, Manchester Research Station 2 US Bureau of Reclamation, Snake River Area Office 3Idaho Department of Fish and Game Eagle Fish Hatchery

  2. Acknowledgements

  3. Outline • Describe hydraulic redd sampling (HRS) • Evaluate embryo collections • Compare HRS with artificial spawning • Estimate embryo mortality caused by HRS • Estimate effective population size in captive rearing program that used HRS • Discuss pros and cons of HRS

  4. Changing goals of salmon and steelhead hatcheries • Producing fish for fisheries • Artificial spawning to meet egg collection goals • Maximize smolt production at a given facility • Meet smolt release goals • Rebuilding natural populations • Avoid ‘mining’ the natural population • Consider carrying capacity in release abundance • Maximize genetic diversity in captive population • Maintaining adaptive genetic variation in the captive population

  5. Hydraulic redd sampling Two approaches Artificial spawning

  6. Hydraulic redd sampling

  7. Hydraulic sampling

  8. Collect eyed embryos Collect eyed embryos Rear and release age-2 smolts Rear and release adults Rear and release adults Production goal = 300 adults Production goals = 4,000 – 30,000 smolts = 200 – 400 adults Captive rearing programs Salmon River Chinook SalmonHood Canal Steelhead (6 years of data for each of 2 populations) (1 – 3 years of data for each of 4 pop’s)

  9. Embryo collection success

  10. Viability and survival in culture

  11. Compare the ‘effective number of breeders’ represented in the captive population under: • Artificial spawning (assuming 1:1 mating) • Hydraulic sampling

  12. Population size (N) and breeders represented in embryo collection (B) Assumptions and estimates Chinook salmon 1.0 female per redd (Bentzen et al. 2001) N = # redds observed x 2 (i.e.,1:1 sex ratio) B = # redds represented in egg collection x 2 Steelhead 0.67 females per redd (Kuligowski et al. 2005, Berejikian et al. 2005) N = # redds observed x 0.67 x 2 (i.e.,1:1 sex ratio) B = # redds represented in egg collection x 0.67 x 2 Both Species 4,000 eggs per female

  13. Targeting release numbers What proportion of the breeding population would be represented to produce the target number of offspring? Steelhead

  14. Targeting release numbers What proportion of the breeding population would be represented to produce the target number of offspring? Chinook salmon

  15. Targeting number of breeders How many eggs would be spawned to obtain the genetic representation that was obtained by hydraulic sampling? Steelhead

  16. Targeting number of breeders How many eggs would be spawned to obtain the genetic representation that was obtained by hydraulic sampling? Chinook salmon

  17. Estimated maximum mortality from hydraulic sampling • Egg-to-fry mortality = 30% • Natural mortality? • Sampling induced mortality?

  18. Effective population size (Ne) Concerns with captive breeding programs: 1) Programs may be founded with a small number of breeders 2) Amplifying a small number of breeders can cause decreases in Ne 3) Reductions in Ne can lead to increased rates of genetic drift and inbreeding Ryman, N. and Laikre, L. 1991. Cons. Biol.

  19. Changes in effective population size in Hamma Hamma River Steelhead (from Van Doornik et al. in prep)

  20. Hydraulic Redd Sampling

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