[env-trinity] CBB: Research Indicates Wild Fish Conservation Best Served By Minimizing Wild/Hatchery Interactions

[Sari Sommarstrom]

THE COLUMBIA BASIN BULLETIN:
Weekly Fish and Wildlife News
www.cbbulletin.com
March 25, 2011
Issue No. 568

* Research Indicates Wild Fish Conservation Best 
Served By Minimizing Wild/Hatchery Interactions

An exhaustive look at available data for 89 
populations of chinook and coho salmon and 
steelhead shows that productivity in the wild 
shrinks in direct proportion with increases in 
the percentage of hatchery fish that join wild fish on the spawning grounds.

“Our results suggest that the net reproductive 
performance of the population will decline under 
all of the hatchery scenarios,” according to 
“Reduced recruitment performance in natural 
populations of anadromous salmonids associated 
with hatchery-reared fish,” a research paper 
published in the March 2011 edition of the 
Canadian Journal of Fisheries and Aquatic 
Sciences. The paper was authored by Mark Chilcote 
of NOAA Fisheries and Ken Goodson and Matt Falcy 
of the Oregon Department of Fish and Wildlife.

The paper can be found at: http://cjfas.nrc.ca

“While using hatchery fish in the short-term to 
reduce extinction risk and temporarily boost 
depressed wild populations to re-establish 
normative biological function are laudable 
conservation roles, such actions come at a cost 
in terms of reductions in per capita recruitment performance,” the paper says.

“Therefore, we conclude, as did Chilcote (2003) 
and Nickelson (2003), that under most 
circumstances the long-term conservation of wild 
populations is best served by the implementation 
of measures that minimize the interactions between wild and hatchery fish.

When considering the bookends ­ a totally wild 
spawning population vs. a spawning population 
comprised 100 percent of fish from hatchery 
origins ­ the conclusion was stark. The hatchery 
populations on average produced only 12.8 percent 
of the recruits (the number of fish that have 
matured in the ocean as counted before they 
encounter fisheries) produced by the wild population.

“The effect of hatchery fish on reproductive 
performance was the same among all three species. 
Further, the impact of hatchery fish from ‘wild 
type’ hatchery broodstocks was no less adverse 
than hatchery fish from traditional, domesticated broodstocks.

“We also found no support for the hypothesis that 
a population’s reproductive performance was 
affected by the length of exposure to hatchery 
fish,” the paper says. “In most cases, measures 
that minimize the interactions between wild and 
hatchery fish will be the best long-term 
conservation strategy for wild populations.”

The analysis shows that it’s wise to “keep the 
hatchery fish off the spawning grounds as much as 
possible if the goal is to rebuild the wild 
population,” said Goodson, the ODFW’s Conservation Planning coordinator.

“We kind of suggest that supplementation might 
not be the way to go,” in many cases, Goodson said.

“If the fish are going to wink out because there 
are problems” that won’t be remedied in the 
shorter-term, supplementing wild populations with 
hatchery fish may be necessary, Goodson said. “In 
some cases that is all we can do.” But the paper 
advises that such decisions should be weighed carefully.

“Supplementing natural spawning areas with 
hatchery fish to benefit the local wild 
population is a conservation tool that has seen 
widespread use in the Pacific Northwest (ISAB 
2003),” the paper says. “The intent of this 
activity includes re-establishing natural 
production in vacant habitats, lessening the risk 
of demographic extinction for wild populations, 
ensuring the available habitats are seeded to 
full capacity, and maintenance of genetic lineages.

“Depending on the circumstances there is a 
balance between risks and benefits that 
conservation managers must accurately assess and 
act on if supplementation programs are to be 
successful and achieve their intended effect,” the paper says.

The analysis indicates that using wild fish as 
broodstock in so-called integrated programs does 
not necessarily make a more wild-friendly hatchery fish.

“Surprisingly, we found that neither length of 
time exposed to hatchery fish nor hatchery type 
has any effect on a population’s intrinsic productivity,” the paper says.

“The incorporation of wild fish into hatchery 
broodstocks has been undertaken with the 
expectation it will ensure that the hatchery fish 
produced will be genetically similar to the local wild fish.

“Therefore, it is assumed that such genetically 
similar hatchery fish, if they escape capture and 
spawn in the natural habitat, will not harm, and 
may in fact benefit the conservation of the wild population.

“Use of wild fish for hatchery broodstock is a 
cornerstone of hatchery reforms currently being 
implemented for salmon and steelhead hatchery 
programs across much of the Pacific Northwest 
(USFWS 2010),” the paper says. “However, our 
findings call into question the effectiveness of 
this path as a means to lessen the impact of 
hatchery programs on wild populations.”

For the analysis the researchers selected 93 
populations (four later were dropped for a 
variety of reasons) of anadromous salmonids from 
the states of Oregon, Washington and Idaho that 
were known to contain both wild and hatchery fish.

They employed annual estimates from 1981 to 2000 
of parental (spawner) abundance for each 
population that were based on information sources 
that differed by species and region. They then 
estimated the proportion of hatchery fish in the natural spawning population.

The next step was to estimate the “preharvest 
number of adult progeny (recruits) naturally 
produced by each brood year of spawners using the 
following four-step process,” the paper says.

“First, we estimated annual return abundance by 
dividing the fishery survival rate, calculated as 
1 - fishery mortality rate, into the observed 
number of wild spawners. Next, we split each 
return into age categories, on the basis of the 
assumed proportion of different age at maturity for each population.

“A table of return estimates by each age category 
was then constructed, and members produced by 
each brood year were identified,” the paper says. 
“Finally, all members of each brood year were 
totaled to yield an estimate of recruits.”

“Our primary finding is that across a broad 
geographical range and three different species, 
Ph (the percentage of hatchery fish on the 
spawning ground) was a population characteristic 
that is negatively associated with reproductive performance,” the paper says.

“Intrinsic productivity declines as the fraction 
of the hatchery spawners in the natural population increases.

“We came to this conclusion after considering 12 
different models that attempted to weigh the 
effect of four other covariates in addition to Ph.”

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