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ISAB Responds to Question
of Excess Hatchery Fish

by Bill Bakke
NW Fishletter, February 21, 2003

The panel of independent scientists that reviews salmon recovery efforts in the Northwest says the recent large returns of hatchery fish may create big problems for ESA-listed salmon. The group explained their position and made recommendations in the December 2002 issue of Fisheries, a journal published by the American Fisheries Society.

Their review was prompted by a request from NOAA Fisheries. The agency was concerned about effects on ESA stocks of large returns of non-native hatchery spring chinook to Columbia River tributaries like the Methow River in northeast Washington. Strong local support for allowing hatchery chinook to spawn naturally with ESA-listed wild chinook was a major reason for the requested review.

But the Independent Scientific Advisory Board didn't pull any punches. "We believe the available empirical evidence demonstrates a potential for deleterious interactions, both demographic, and genetic, from allowing hatchery-origin salmon to spawn in the wild."

A plan to limit the natural spawning of hatchery spring chinook with wild spring chinook in the Methow was "protested by basin tribes and others who believed that allowing these hatchery-origin fish to spawn would help recover listed populations," say the authors, who also mentioned earlier public opposition to clubbing hatchery coho at an Alsea River hatchery in Oregon that led to several lawsuits and an effort to repeal the wild fish policy in Oregon.

The authors also noted the concern of Klamath River tribes and watershed groups over the straying of hatchery salmon after too many fish returned to California hatcheries. The tribes and public were concerned that the huge numbers of hatchery fish would swamp restoration efforts of the wild stock. The state responded by killing the excess hatchery fish.

"The scientific evidence does not support indiscriminately permitting hatchery-reared salmon to spawn naturally throughout the Columbia River Basin," said the ISAB after a careful and extensive discussion of the literature.

Though some groups support using hatchery salmon to rebuild wild salmon populations, the ISAB found little support for such strategies. "We are not aware of studies that demonstrate that reproduction by stray adult salmon from conventional hatchery programs makes meaningful contributions to the abundance of naturally spawning salmon populations," they said, noting also that they were not aware of peer-reviewed studies that demonstrated successful supplementation efforts.

The life history variation among populations of salmon is the result of the genetic structure of a population affected by natural selection in a constantly fluctuating environment. When salmon from two genetically divergent populations interbreed, their progeny could have lower survival fitness than the parents through the loss of local adaptations to the environment. It's a factor called "outbreeding depression" and the authors said "it could happen when hatchery salmon of non-local source spawn with local wild salmon."

The paper also discussed domestication selection, where hatchery salmon are selected for traits that fit the hatchery environment, making them less fit for survival in the natural environment. The ISAB authors said, "...domestication selection within hatcheries can lead to genetic divergence of wild and hatchery salmon from the same ESU [Evolutionarily Significant Unit]." They noted the considerable variation among salmon culture programs in the past and that present hatchery stocks "likely vary widely in their degree of domestication."

The authors reviewed a number of studies that indicated a change in reproductive success in hatchery salmon compared to wild salmon. "...These experimental results," said the ISAB, "...provide convincing evidence that

  1. Domestication selection can genetically alter hatchery populations in a relatively few generations;
  2. Hatchery-reared adults returning from the ocean and spawning in the wild generally produce progeny that do not survive as well as progeny from adults of wild origin;

    and persuasive indication that

  3. Interbreeding between hatchery-reared adults and wild fish can reduce the fitness of wild populations."

In response to the scientific evidence at hand, the ISAB recommended that a precautionary approach be taken. They suggested that "management actions be reversible if found to yield unintended results. Because it is virtually impossible to undo the genetic changes caused by allowing hatchery and wild salmon to interbreed."

The Methow River has two distinct populations of wild, ESA-listed spring chinook. One is found in the Chewuck River and the other is found in the Twisp, but the Carson stock of spring chinook used in the hatchery program is not native to the Methow River or its tributaries and is not included in the spring chinook ESU for these rivers. Even though the ISAB opposed letting the Carson spring chinook spawn naturally in the Methow, a negotiated compromise was made with interest groups and fish managers to allow these hatchery fish to spawn in the mainstem Methow River.

"We allowed fish that were not necessary for brood stock to spawn naturally in the river, but took steps to reduce risk by releasing Carson Hatchery spring chinook juveniles into the Okanogan River," said NOAA Fisheries' Kris Petersen. In addition, NOAA Fisheries, along with the management agencies, are building a local brood stock using Chewuck and Twisp stocks for the hatchery program.

"After 2001," Petersen said, "Carson spring chinook were not released into the Methow, but returning adults were allowed to spawn in the mainstem Methow, but not in the tributaries where they would interbreed with ESA-listed spring chinook." This year will be the last year where Carson spring chinook will return to spawn in the mainstem Methow.

Monitoring and evaluation are necessary to provide the means by which changes in management actions are accomplished, but monitoring alone is not sufficient. The ISAB cited two documents that identified monitoring problems: the 2000 Biological Opinion and the Basinwide Recovery Strategy from the Federal Caucus. "...both conclude that they are unable to assess the impacts of hatchery releases on wild populations because of insufficient monitoring and evaluation of past activities. Given this problem, the authors said a "well-designed, large scale experiment designed specifically to assess the effects of hatchery-derived spawning on wild populations is needed. It is time to implement such an experiment."

"There are still several outstanding questions about hatcheries that need to be answered," said co-author Jim Lichatowich, "and the fact that they have not been answered after 126 years of using hatcheries is a sign of failure at several levels of salmon management. One key question is if it is assumed that hatchery and wild salmon are equivalent in nature, then that must be verified." He has said if they are not equivalent, then hatchery and wild salmon must be isolated in the ecosystem.

Bill Bakke
ISAB Responds to Question of Excess Hatchery Fish
NW Fishletter, February 21, 2003

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