Study Shows Conflicts in Hatchery Production/
Efforts to balance hatchery production for harvest with aims to protect the genetic "integrity" of naturally producing salmon and steelhead populations must be carefully orchestrated scientifically, and in some cases may be difficult if not impossible to achieve, according a recently published paper that analyzes data from a southwest Washington steelhead supplementation project.
". . . if conservation issues are determined to be the most important issue for hatchery propagation, then production goals may need to be forfeited," according to the research article, "Loss of Genetic Integrity in Hatchery Steelhead Produced by Juvenile-Based Broodstock and Wild Integration: Conflicts in Production and Conservation Goals." It was published online May 27 in the scientific journal, North American Journal of Fisheries Management.
Corresponding author is Daniel M. Bingham. Contributing authors are Benjamen M. Kennedy, Kyle C. Hanson and Christian T. Smith. At the time of writing all were based at the U.S. Fish and Wildlife Service's Abernathy Fish Technology Center, 1440 Abernathy Creek Road, Longview, Wash. Bingham is now a private consultant .
"In summary, it's a long-term case study showing that many of the currently touted conservation-based hatchery protocols conflict with production goals, resulting in loss of genetic integrity in hatchery fish," Bingham said of the study analysis.
"The goal of this study was to evaluate whether broodstock management at the AFTC hatchery maintained wild-type genetic characteristics in hatchery fish used to supplement the steelhead population in Abernathy Creek," the research paper says. "Specifically, we analyzed 10 microsatellite loci to compare effective sizes, genetic diversity, and genetic divergence among juvenile-based broodstock, wild smolts, and hatchery juveniles across 11 brood years.
"We expected that genetic characteristics of hatchery fish would approximate those of the wild fish if the protocol was effective."
The AFTC hatchery is located on southeast Washington's Abernathy Creek, which enters the lower Columbia River about 145 kilometers downstream from the lower Columbia River's Bonneville Dam and 90 km upstream from the Pacific Ocean.
Propagation of winter steelhead using endemic steelhead began in 1999, which is when juveniles were first brought into the hatchery to be raised for broodstock. Prior to this time no steelhead production took place on Abernathy Creek, but stray hatchery and wild steelhead were common in the system.
Hatchery fish were produced at AFTC using broodstock comprised of endemic juveniles that were caught in the wild (1999-2001; collected as age-0 parr) and raised to maturity for three consecutive years (2002-2004; bred as age-3 adults).
Then the program transitioned to an integrated broodstock comprised of adult wild and hatchery fish that returned to spawn (2005-2010). Additional husbandry techniques designed to reduce genetic drift and selection were attempted, including production of at least 70 families, use of one-to-one pairwise crosses between males and females, equalization of family sizes, and integration of at least 10 percent wild fish into the broodstock each year.
"We examined whether a supplementation program for steelhead Oncorhynchus mykiss in southwesternWashington could produce hatchery fish that contained genetic characteristics of the endemic population from which it was derived and simultaneously meet a production goal," the research paper says.
"Importantly, some auxiliary conservation-based husbandry protocols were attempted (i.e., pairwise mating between males and females) but not always completed due to insufficient broodstock and conflict between production and conservation goals," the paper says. "The hatchery met production goals in 6 of 9 years, but wild-type genetic integrity of hatchery fish was degraded every year."
"Specifically, we analyzed 10 microsatellites and observed a 60 percent reduction in the effective number of breeders in the hatchery . . .. Hatchery fish consequently displayed reduced genetic diversity and large temporal genetic divergence compared with wild counterparts."
The ideal would be to provide plenty of hatchery fish for harvest, while assuring the genetic integrity of wild, naturally produced fish that are in most situations off limits to sport and commercial fishers.
Many of those wild salmon and steelhead are protected under the Endangered Species Act and at relatively low population levels.
"Despite substantial conservation-based husbandry efforts, hatchery steelhead rapidly diverged from the wild component," the paper concluded.
Four significant management-based conclusions can be drawn from the study analysis, according to the article.
"First, juvenile-based broodstock conjoined with equal-family contribution and pairwise mating did not produce F1 hatchery offspring with wild-type genetics. In contrast, the juvenile-based broodstock itself seemed to reasonably represent the genetics of wild fish.
"Thus, the mating scheme did not capture the effective size and diversity of the juvenile-based broodstock population or natural reproduction.
"Second, the number of wild fish used as broodstock had significant positive effects on genetic diversity and effective population sizes of hatchery fish. Prior to implementing husbandry focused on increasing wild spawners in broodstock, however, managers should weigh the possible impacts of 'broodstock mining' and 'Ryman-Laikre' effects.
"Third, the literature review conducted in this study highlights that inconsistency in the ability of conservation-based husbandry to mitigate for genetic consequences could partially stem from the diversity of conditions, practices, and goals present in conservation-oriented supplementation programs.
"We therefore recommend that critical information regarding gene flow between the hatchery and wild components, and also information on demography (e.g., number of spawners, sex ratios), be presented and considered to allow more conclusive inferences across studies.
"Finally, the AFTC hatchery management plan was designed to meet production and conservation goals with no real knowledge regarding its ability to obtain sufficient broodstock or to implement conservation-based hatchery protocols. To ensure the benefit of conservation efforts, major logistical issues need to be seriously considered. Foremost, spawning protocols should be based on both realistic expectations for the availability of spawners and on scientific theory," the article says.
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