steelhead spawners are unlikely to contribute measurably to the natural
productivity of a mixed population of hatchery and wild fish unless natural
spawner abundance is generally below carrying capacity, according to a new
Brent Lister, a consulting fisheries biologist in British Columbia, studied the
census data of six Columbia River populations of summer steelhead, all with
mixed populations of hatchery and wild steelhead, and published his findings,
“Natural Productivity in Steelhead Populations of Natural and Hatchery Origin:
Assessing Hatchery Spawner Influence,” in the Jan. 9 Transactions of American
steelhead populations he studied were from the Deschutes, Warm Springs and
Umatilla rivers in Oregon, the Yakima River in Washington, and Joseph and
Little Sheep creeks, tributaries of the Imnaha River in northeast Oregon.
since Columbia and Snake river steelhead were listed as threatened under the
Endangered Species Act in late 1990s, biologists and ecologists have worried
about the threat of spawning hatchery fish on spawning native or wild
steelhead, Lister said.
other than DNA analyses over the last eight years, any negative impact of
hatchery on wild steelhead had not been shown.
the purpose of the study was to determine the influence of hatchery steelhead
spawners on the productivity of natural spawners in populations in mixed stock
and wild steelhead spawners can interbreed when both are present. Although
hatchery steelhead produced from native broodstocks can exhibit reproductive
fitness approaching that of natural spawners, over the long term as hatchery
fish are further in time from their broodstock origins, “the presence of
less-productive hatchery spawners may therefore result in reduced population
has led to such initiatives as one proposed by the Washington Department of
Fish & Wildlife in December. The WDFW proposal is to eliminate the release
of all hatchery-raised steelhead on the East Fork Lewis River and the North
Fork Toutle/Green River watershed as early as this year in order to “preserve
key wild steelhead populations by minimizing interference by hatchery-produced
fish." (CBB, Dec. 6, 2013, “WDFW Proposes Ending Steelhead Hatchery
Releases In Three Columbia Tributaries To Boost Wild Fish” (http://www.cbbulletin.com/429220.aspx)
has been working on this research since 2005, when he received funding for the
study from the Yakima Basin Joint Board, a coalition of irrigation districts in
central Washington near Yakima.
he found while studying census data of summer steelhead was that if the native
population is at carrying capacity, the presence of hatchery spawners has a
minimal impact on later adult returns. In fact, five of the six streams and
populations he studied contained apparent healthy stocks of wild steelhead that
Lister believes were operating at or near carrying capacity.
Deschutes River, for example, has a high incidence of stray hatchery fish. As
the Columbia River water heats up in the summer, these fish will move up into
the cooler Deschutes River. Many will stay and spawn, some will find their way
back to the mainstem Columbia River to move up to Columbia River and Snake
River hatcheries upstream from the Deschutes River.
with the numbers of hatchery fish present, Lister found no net impact on
five generations of exposure to stray, multiple-generation hatchery spawners of
local and nonlocal origin, there was no apparent effect on Deschutes natural
steelhead productivity and status,” he wrote.
came to the same conclusion in the Umatilla River, as well as the other rivers
in the study, with the exception of Little Sheep Creek. Little Sheep Creek,
along with the Umatilla River, are watersheds where hatchery supplementation is
there is not a full complement of wild spawners, however, the hatchery fish can
gain a foothold,” he said. That is what he saw in Little Sheep Creek, where
hatchery spawners were 73 percent of the spawning steelhead, but contributed
just 44 percent to mean productivity while wild spawners contributed 56 percent
study is available at the American Fisheries Society website at: http://www.tandfonline.com/doi/abs/10.1080/00028487.2013.824919#.UuGhDb7TnIU