The effects of domestication on predation vulnerability
Background
- Hatcheries may increase survival of fish with certain genetic traits that are maladaptive in the natural environment (relaxation of natural selection)
- Survivors can pass on these traits to their offspring and reduce the productivity of the naturally reproducing population
-
Purpose
- Is there differential predation mortality between the offspring of conventional hatchery and a supplemented population of spring Chinook salmon that could be the result of domestication selection?
Supplementation
- The offspring of natural origin adults in the supplemented population of the upper Yakima
- Parents could be any combination of returning, marked hatchery adults and unmarked naturally spawned adults
- Returning marked adults that were reared in the hatchery must spawn in the river (integrated population - at least one generation of natural selection between hatchery rearing)
Hatchery
- The offspring of hatchery origin adults in the upper Yakima River-started with BY02 marked adults
- Not allowed past Roza Dam to spawn (segregated - no natural selection in early life)
Naches
- Serve as a baseline for domestication – no history of hatchery influence
- Adults collected and spawned in September 2005, incubated to eyed stage in mister boxes, transferred to CESRF after pathogen screening
Hypothesis
Methods
- Used the juvenile offspring of three different lines of spring Chinook salmon that were reared identically in the hatchery (common garden experiment)
8 - 3m x 2.4m x 1.5m 3mm mesh net pens in a raceway were stocked with 2 rainbow trout and 2 torrent sculpins
- 8 - 3m x 2.4m x 1.5m 3mm mesh net pens in a raceway were stocked with 2 rainbow trout and 2 torrent sculpins
- Size matched 50 fry of each origin, marked them, and released into each of the net pens
-
At end of each trial survivors were recovered and enumerated
- At end of each trial survivors were recovered and enumerated
- Used the Wilcoxon matched pairs test for survival between origins (H vs. N, S vs. N, H vs. S)
Sculpin Trials
- Stocked 1 individual from each origin (size-matched) into glass aquaria divided into a safe zone (1/3 of tank, no food) and a predator zone (2/3 of tank, food)
- Stocked 1 torrent sculpin into each tank on second day
- Fed fry for each of six days
- Tested for differences in survival (sign test) and percent growth by weight of the survivors (ANOVA)
Results – Net Pens
Yearly Survival Difference
Results – Sculpin Trials
Summary
- Agrees with the hypothesis of domestication (survival; N > H, S > H, N > S)
- Differences are still small
- Good news for integrated supplementation programs?
- May not see the same thing each year because of annual variation (e.g. 2005)
- Will continue sculpin trials in 2007 (slightly modified) as a backup to the net pen trials
Literature
Acknowledgements
- USFWS - Ray Brunson, Joy Evered, Sonia Mumford
- YN - David Fast, Germaine Hart, Ted Martin, Sara Sohappy, Ann Stephenson, Charles Strom and CESRF Staff
- WDFW – Edward Beall, Charity Davidson, Christopher Johnson, Curt Knudsen, Natalia Pitts, Gene Sanborn, Steve Schroder, Gabriel Temple, Marilee Webster, Timothy Webster
- BPA – Patty Smith, David Byrnes