2003-054-00

Evaluate the Relative Reproductive Success of Hatchery-Origin and Wild-Origin Steelhead Spawning Naturally in the Hood River

BACKGROUND
(see bibliography of our BPA funded publications in attachments file “Bibliography to 2016”).

Hood River steelhead spawn only above the former Powerdale Dam, which was a complete barrier to all salmonids. From 1991 until the dam was removed in summer of 2010, every adult passed above the dam was measured, cataloged, and sampled for scales or fin snip. We used those samples to create a 4-generation pedigree of winter run fish that we used to analyze the fitness of winter run hatchery and wild fish. The main results are firstly, that the old, domesticated “Big Creek” stock of winter-run fish had very poor fitness (~10% reproductive success, relative to wild fish) and the newer, F1, stock averaged about 85% relative reproductive success. Secondly, F2 (second generation) hatchery fish had half the fitness of F1 fish raised side-by-side with them in the same hatchery. This result implies a genetically-based decline in fitness. Thirdly, we also found that wild-born offspring of two F1 hatchery fish averaged 37% the fitness of the offspring of two wild fish, while offspring of hatchery-by-wild crosses averaged 87%. Again, this result suggests a genetically-based effect. We also showed (1) that F1 fish made better broodstock than wild fish (in terms of per-capita production of returning hatchery offspring), and (2) that there was a tradeoff among wild broodstock in which those that performed best in the hatchery produced offspring that performed worst in the wild, and vice versa. Finally, we see large differences between the offspring of wild and hatchery fish, raised under identical conditions, in patterns of gene expression. Thus, a large amount of empirical data suggest that very strong domestication selection in that hatchery made winter run fish quickly adapt to the hatchery, with negative consequences for performance in the wild. A meta-analysis of RRS studies from other species and rivers suggests this is a general phenomenon, and not peculiarity of steelhead or the Hood River.

QUESTIONS TO BE ANSWERED: What is the mechanism of domestication?
Our main efforts are now focused on figuring out what are the selection pressures in the hatchery that cause rapid domestication, and what aspects of hatchery culture exacerbate that selection. If we could answer those questions, then it might be possible to modify the hatchery environment to produce hatchery fish that are more like wild fish. That is our current goal. Towards that end, we are currently pursuing three lines of research.

(1) Test effects of modifying hatchery rearing conditions:
Here we vary environmental conditions in the hatchery that we suspect might exacerbate selection (e.g. density, feeding methods, environmental complexity). Then we test whether the modified conditions produce fish that show less variation among families in performance in the hatchery than do the standard conditions. Under standard conditions we see large variance among families in size at release, which means large opportunity for selection (larger smolts are more likely to return as adults, so we use size at release as our measure of performance in the hatchery). If we can find environmental conditions that reduce that variance, then there would be less selection among families, and a slower rate of adaptation to the hatchery.

(2) Identify trait variation among families that correlates with their performance in the hatchery:
We hypothesize that what is under selection are traits that enhance an individual’s ability to grow quickly in the novel environment of a hatchery. So the second approach has been to test candidate behavioral and physiological traits that might enhance growth. To date we have shown that fast growing families tend to be more dominant than slow growing families, and we are currently testing whether other measures of boldness and activity correlate with family growth rate.
We are also looking at genome-wide patterns of gene expression in the siblings of each family that is being raised in growth rate experiments (gene expression means how actively each gene is being transcribed to make proteins). Then we test whether expression levels of any sets of genes predict which families grow the fastest. The idea is that identifying suites of genes that predict growth rate under hatchery conditions might point us to the traits that are under selection.

(3) Genome scans:
The third approach is to do genome-wide scans of wild fish and first-generation hatchery fish in order to identify genes that may have responded to selection. The idea is, again, that finding such genes may point us to the traits that were under selection. There are two ways to do genome scans: gene expression analysis and genome-wide association studies (GWAS). We are currently undertaking both types of studies.

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2004

2020

Maureen Kavanagh

Implementation - Project Status Report

Province	Subbasin	%
Basinwide	-	100.00%

Artificial Production

RM and E

Steelhead - All Populations
Steelhead - Lower Columbia River DPS

Anadromous: 100.0%   Resident: 0.0%   Wildlife: 0.0%

RM&E Plus Cat. Review - Submitted and Reviewed (Public Tags)
RME/AP Categorical Review (Public Tags)
Council Recommended Projects (Public Tags)

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RPA 64.2 Determine if artificial production contributes to recovery,
RPA 64.1 Estimate relative reproductive success (RSS) of hatchery