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Research: Non-Native Fish -- Bass, Walleye
Pose Substantial Threat To Salmonids

by Staff
Columbia Basin Bulletin, March 6, 2009

Non-native, predatory species such as bass and channel catfish may pose as great a threat to imperiled Columbia River salmon and steelhead as do such factors as harvest and the hydro system, yet invasive fish have largely been ignored, according to Northwest Fisheries Science Center research published this week.

"Where data exist, we quantified the impact of non-indigenous species on threatened and endangered salmonids," according to the abstract for the article, "Non-indigenous Species of the Pacific Northwest: An Overlooked Risk to Endangered Salmon?" published in the March edition of BioScience.

Beth L. Sanderson of the Northwest Fisheries Science Center in Seattle is lead author for the paper. Contributing to the effort were Katie A. Barnas and A. Michelle Wargo Rub.

"The results indicate that the effect of non-indigenous species on salmon could equal or exceed that of four commonly addressed causes of adverse impacts -- habitat alteration, harvest, hatcheries, and the hydrosystem; we suggest that managing non-indigenous species may be imperative for salmon recovery."

Many native fishes in the Pacific Northwest, including 13 Columbia Basin salmonid stocks, are listed as threatened or endangered under the Endangered Species Act.

"Despite the clear evidence that invasive fishes have a substantial impact on economically important salmonids, Sanderson and colleagues note, only a very small percentage of research funding is devoted to examining the threat that non-indigenous species pose to native communities," says a press release announcing contents of BioScience's March edition.

"... we do not know enough about NIS impacts on native species to make educated prevention and management decisions. This lack of information is especially of concern with regard to threatened or endangered species," the paper says.

The article can be found at:

As part of their study, the NWFSC researchers analyzed 2007-2009 spending by the Bonneville Power Administration through the Northwest Power and Conservation Council's Columbia River Basin Fish and Wildlife program. The survey indicated that of the $385 million spent; only 0.3 percent was for evaluation of non-indigenous fish species (NIS) impacts, and less than 1 percent was allocated for efforts to control NIS.

"A greater proportion of funding (approximately $20 million, 5.2 percent) was spent on projects dedicated to the control and removal of noxious weeds and important native predators (e.g., pikeminnow and avian predators such as terns and cormorants)," the NWFSC paper says.

"Pikeminnow are clearly the biggest predator" among the Columbia's fish species, but the impacts of NIS species are notable as well, Sanderson said.

Another $560,000 was spent on projects to introduce or maintain non-native fish stocks.

"Management agencies are becoming more cautious about introducing and stocking non-indigenous fishes, yet the continued stocking of some non-indigenous fish species reflects the high value attached to sport fisheries in this region," the new NWFSC paper says.

More research is needed to better evaluate the impact of NIS on salmon, and develop management strategies to reduce those impacts, according to the article.

"We're not interested in taking on the recreational fishing industry," Sanderson said. Many of the introduced stocks, such as bass and walleye in the Columbia and Snake rivers, are prized fisheries regulated by the states.

The paper concludes that broader assessments of NIS impacts are needed to help guide management that reduces predation on salmonids, according to Sanderson.

"Considering the percentage of funds allocated to NIS research and the results of our review of impacts, the level of attention given to NIS seems disproportionately small, given the magnitude of the potential threat that NIS pose to native communities," the paper says.

The idea that more knowledge and action is needed appears to be gaining momentum. The Independent Scientific Advisory Panel in a July report recommended that the NPCC and the fish and wildlife agencies in the basin "elevate the issue of non-native species effects to a priority equivalent to that of habitat loss and degradation, climate change, and human population growth and development." The ISAB was formed to provide scientific advice to the Council, basin tribes and the NOAA Fisheries Service, which listed the 13 stocks and is responsible for building salmon recovery plans.

The NPCC in amendments to its fish and wildlife program approved in early February "acknowledges invasive non-native species pose direct threats to the Program's fish and wildlife restoration efforts through competition, predation and habitat modification."

NOAA Fisheries in its May 5, 2008, Federal Columbia River Power System biological opinion says it will work with federal dam operators, states and tribes to "coordinate to review, evaluate, and develop strategies to reduce non-indigenous piscivorous predation." The formation of a workshop will be an initial step in the process."

The BiOp's reasonable and prudent alternative No. 44 says that beginning in 2010, annual progress reports will describe actions taken as a result of the workshop. The BiOp describes mitigation measures intended to improve the survival of listed salmon and steelhead and assure those fish stocks aren't jeopardized.

A workshop was held in September. According to notes from the session, participants identified three distinct areas of focus for "next steps": (1) development of a "problem statement", (2) identifying additional information needs and (3) identifying the partners needed to help make progress.

An initial list of objectives developed at the meeting focused almost entirely on the need to develop more information about NIS impacts and on possible strategies for "modifying non-native piscivorous predation dynamics."

The research paper released Monday drew its conclusions after assembling all known occurrence and distribution records on non-indigenous species found in roughly 1,800 square kilometers of hydrologically connected areas throughout Washington, Oregon and Idaho.

The spatially explicit database the NWFSC researchers compiled from these records indicates that NIS -- the majority of which are plants and fish -- are present in all of those connected areas, with as many as 486 in some watersheds.

The researchers examined the extent to which introduced species are a risk to threatened and endangered salmon and identified all documented NIS in the Pacific Northwest, including fish, invertebrates, birds, plants, and amphibians.

The new article cites past research that documents NIS as one of the dominant environmental threats to biological diversity and a cause of the downfall of 48 percent of the listed species overall, and 70 percent of listed fish species, in the United States. Another study pegged the NIS cost to the U.S. economy in 2005 alone at $120 billion "and the occurrence and ranges of NIS are steadily increasing," the paper says.

The status of freshwater aquatic fauna is especially dire, Sanderson and colleagues report. In particular, non-indigenous fishes compete with or prey on native fishes, posing a serious threat to the persistence of the natives.

Sanderson and colleagues assembled reports of predation by six of the 60 non-iondigenous fish species found in the region: catfish, black and white crappie, largemouth bass, smallmouth bass, walleye, and yellow perch. The researchers estimate that NIS are now in the majority, representing 54 percent, 50 percent, and 60 percent of the fish species found in Washington, Oregon, and Idaho, respectively.

A review of published and gray literature found 27 existing studies that quantified NIS predation to some degree.

"Of those studies reporting the number of juvenile salmon eaten by individual NIS predators, we found values that ranged from zero to 10.4 million (median value = 5.2 million), with many studies reporting hundreds of thousands of juveniles consumed by a single NIS predator species at a specific study site in the Columbia River basin," the article says. "At locations in the Columbia River, smallmouth bass and walleye consumed between 18,000 to 2,000,000 and 170,000 to 300,000 juvenile salmonids per year, respectively."

"By synthesizing data on the spatial distribution and known impacts of NIS on salmonids throughout the Columbia River basin, we can begin a discussion of the overall effects of these NIS," the report says.

The article says that mortality attributed to NIS predation may be similar to that associated with juvenile passage through each of the eight dams on the Columbia and Snake rivers. Likewise it could match or surpass productivity declines attributed to habitat loss and degradation and to that estimated for in-river harvests.

Research: Non-Native Fish -- Bass, Walleye -- Pose Substantial Threat To Salmonids
Columbia Basin Bulletin, March 6, 2009

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