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Tribes Detail Success, Promise Of Supplementation To Boost Natural Spawning Salmon Populations
Posted on Friday, November 19, 2010 (PST)

“You’re going to find differences in reproductive fitness” between wild salmon and hatchery fish that find their way to the spawning grounds, according to the Yakama Nation’s Bill Bosch.


But better hatchery management practices now being employed that produce fitter fish can mute those differences. And numerous studies show that, when done right, supplementation with hatchery fish can boost natural production, according to Bosch and other tribal spokesmen who on Nov. 9 offered their side of the story to the Northwest Power and Conservation Council.


Can supplementation maintain or increase natural production? Can supplementation hatcheries be managed to maintain the long-term fitness of wild/natural populations? If there are negative hatchery effects, are they reversible?


“Yes,” in all cases, said Bosch, citing a sampling of study results as proof, as well as a 27-page “Bibliography in Support of Supplementation Science,” compiled by staff from the Yakama Nation’s Yakima Klickitat Fisheries Project and Columbia River Inter-Tribal Fish Commission. The commission’s member tribes include the Nez Perce, Umatilla, Warm Springs and Yakama.


“We’re moving in the right direction, according to the Columbia River treaty tribes. We’re moving toward recovery,” Bosch said. “This is what treaty tribes think progress looks like.”


The tribes requested the audience at the November meeting in Portland to provide an update on the tribes’ hatchery supplementation initiatives and to counter a presentation made by NOAA Fisheries’ Michael Ford in September. He cited two decades of research on Pacific salmon that “tend to show poor reproductive success of hatchery fish when they spawn in the natural environment” and that those hatchery fish can have negative impacts on wild juveniles and spawners. (See CBB Story “NOAA: Research Indicates Hatchery Fish Have Poor Reproductive Success When Spawn In The Wild”


NOAA Fisheries is charged with protecting wild salmon and steelhead stocks that are listed under the Endangered Species Act. Many of the tribal hatchery/supplementation programs are funded by the Bonneville Power Administration through the Council’s Columbia River Basin Fish and Wildlife Program.


CRITFC Executive Director Paul Lumley said the NOAA presentation focused on linking negative happenings to supplementation while the tribes’ approach is to use continually updated science to “make hatchery programs work to the benefit of wild fish. It’s not all negative; we have had some tremendous successes” with upriver populations.


“Like it or not we’ve had some success,” Lumley said.


According to the Regional Assessment of Supplementation Project definition, supplementation “is the use of artificial propagation in an attempt to maintain or increase natural production while maintaining the long term fitness of the target population, and keeping the ecological and genetic impacts on non-target populations within specified limits.”


It is largely designed to keep populations afloat in the face of other factors that limit salmon, such as mortality from hydro system passage, habitat losses and flow management for power production and irrigation. And human population growth and development needs will continue to put pressure on shared habitat and water resources.


There is a need mitigate for those limiting factors in order to fulfill obligations in treaties to provide fisheries and to “help wild populations that aren’t replacing themselves,” Bosch said. Supplementation is necessarily an important tool.


“There aren’t a lot of options,” Lumley said.


Bosch says that increased artificial production has helped what has been somewhat of a resurgence in certain salmon populations. The tribes “had to sit on the bank for 25 years” starting in the early 1970s because there simply weren’t enough spring chinook salmon returning to conduct fisheries. For the past decade and more, fisheries have been frequent.


In central Washington’s Yakima River basin enough fish have returned to allow sport fisheries in 7 of the past 10 years, after 40 years without.


Some of the population growth can be attributed to supplementation, the practice of giving hatchery produced smolts their final rearing at various streamside acclimation sites so that they home in on those areas to spawn naturally when they return as adults.


As an example, an ongoing study shows that redd survey totals for the upper Yakima and Naches rivers (1981 to 2010) indicated that the number of spawners increased for both populations during the post-supplementation period (2001-2010) but the average number of redds increased 245 percent in the upper Yakima vs. 160 percent for the unsupplemented Naches River. That suggests that supplementation increased the number of spawners in the upper Yakima beyond the natural increases associated with improved ocean survival. The number of redds and natural origin spawners has increased in the targeted Teanaway River indicating this approach may be successful for reintroduction of salmonids into underutilized habitat, according to a study synopsis.


The wild population in the unsupplemented Naches “appears to be declining while the upper Yakima is holding its own, replacing itself,” Bosch told the Council.


There are numerous examples in the Columbia River of hatchery fish getting a foothold in the wild, and taking advantage of it, he said. Coho stocks in the Wenatchee and Yakima rivers in Washington and the Clearwater River in Idaho were at or near extinction before being reintroduced by the tribes. Since the mid- to late 1990s reintroductions of the coho populations in those streams have, except for an occasional dip, showed an upward trend.


The tribes have done their best to apply new-found scientific information to raise hatchery fish that more closely mirror the genetics and behavior traits of their wild kin. That includes random, representative selection of local broodstock wherever possible, factorial mating to maintain diversity, low rearing densities and underwater feeders and cover to more closely represent natural conditions and tests of different rearing/release strategies to increase survival.


Bosch said that a new, unbiased review of hatchery program research literature is needed to address concerns about the potential for reduced reproductive fitness among wild fish that interact with wild fish.


One of the graphs presented by NOAA’s Ford in September compared the results from 18 studies that seemed to indicate that the reproductive fitness of hatchery origin fish and of natural salmon with which they interbreed decreases through time and in some cases decreases quite rapidly.


But a review of those studies shows that the researchers may not have adequately considered factors which might have “confounded” the results. In some cases, hatchery fish from non-local sources and/or with a multi-generational record of domestication were compared.


“Supplementation guidelines require use of extant local stock as the source for the hatchery broodstock,” according to a CRITFC “interpretation” of Ford’s graph. “If the open data points [hatchery fish from non-local broodstock] are removed from the graph, a liner regression line fit to the remaining data no longer has a dramatically downward slope, indicating that progressive loss of fitness will be of a much smaller magnitude than initially inferred.”


Likewise there can be confounding environmental effects, rather than genetic, that cause seeming reduced fitness in hatchery fish. Comparing natural origin spawning in optimal habitat with hatchery fish spawning in less ideal conditions tilts the odds in the wild salmon’s favor.


“You’re bound to find differences in reproductive success,” Bosch said.


“Similarly, some of the studies compare performance of hatchery stocks which have been deliberately, or inadvertently, selected for characters which diverge from those of the native stock (e.g., altered run timing). Such changes may be maladaptive, and inclusion in the graph of data from these programs graph biases the results against Supplementation,” the CRITFC analysis said.


One example would be steelhead. Wild/natural fish migrate to sea after 1 to 3 years in freshwater so they are logically more robust and likely to survive to return and spawn, Bosch said. Nearly all steelhead hatcheries operate to produce age-1 smolts. Steelhead also include unique winter and summer populations, which have in some cases been inadvertently hybridized in hatcheries. Making comparisons with wild fish is indeed apples and oranges in many cases.


“Steelhead is not a good species to make broad-based claims about hatchery fish,” Bosch said.


Bosch said the tribes are seeking agreement with others in the region that hatchery programs are to achieve mitigation obligations and to help make progress towards conservation objections. An overarching goal would to improve programs through adaptive management.


“We’re going to keep pressing this scientific position with some of our colleagues,” said Steve Parker, technical staff coordinator for Yakama Nation Fisheries.


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