Scientists studying salmon in the estuaries at the mouth of the Columbia River are warning that hatcheries intended to boost runs of big Chinook may be doing the river’s wild fish more harm than good.
“Overall, the historical replacement of diverse wild populations with fewer hatchery stocks of a narrow size range and migration timing has intensified nearshore habitat use during the spring-summer migration peak and reduced life-history variation of
Columbia River Chinook salmon,” they wrote in the draft of a peer-reviewed paper published online by the North American Journal of Fisheries Management last week. “Such changes could undermine the fish conservation goals of both hatchery mitigation and estuary restoration programs” on the Columbia.
Once the most productive salmon producing watershed in the lower 48 states, the 1,250-mile-long river that flows south from the Rocky Mountains of British Columbia, Canada into the U.S., before turning west to form the border between the states of Washington and Oregon suffered as the country tried to battle its way out of the Great Depression.
“The federal role in damming the Columbia tied in well with the New Deal belief that the government should stimulate economic recovery by putting people to work and encouraging the creation of public utilities,” records a National Park Service history of the river’s Grand Coulee dam. “Franklin D. Roosevelt, elected president of the United States in 1932, asked for plans for a low dam with foundations strong enough to support a higher dam later, one that would back water up to the Canadian border.”
No thought was given to the river’s salmon.
“Of all the impacts that caused extinctions of Columbia River Basin salmon and steelhead, dams were the most significant. And the most significant of the dams, at least in terms of the number of known runs that were extinguished, is Grand Coulee,” according to the Northwest Power and Conservation Council.
“The dam wiped out runs that spawned in tributaries that drained into the Columbia from that point, river mile 596, to the headwaters, a distance of 645 river miles. Adding the tributary miles where salmon spawned nearly doubled the distance. The Bureau of Reclamation, which built the dam, was aware of the impact Grand Coulee would have on salmon and steelhead and took steps to compensate for the losses through the construction of hatcheries. This was complicated, however, by the fact that the upper Columbia salmon runs had been declining for years before the dam finished them off.”
Since then, hundreds of millions of dollars have been spent on hatcheries intended to help save the salmon and, as the new study notes, 13 specific populations of four species of Columbia salmon and steelhead have ended up listed under the Endangered Species Act.
Millions of additional dollars are now being spent on the restoration of estuary habitats, but the study warns the money could be wasted.
“Salmon habitat use in the Columbia River estuary occurs at the intersection of two mitigation programs with different management objectives targeting different subareas of the basin and life stages of salmon: a hatchery program to replace lost habitat and fishery production potential from the interior basin caused by the construction of mainstem dams and a habitat restoration program in the estuary to offset the mortality of naturally produced juveniles caused by the operations of the Federal Columbia River Power System,” the study says. “The considerable spatial and temporal overlap among hatchery origin (HO) and naturally produced (NP) salmon imply a strong potential for interactions in the estuary that are not anticipated by either program but could undermine the salmon conservation goals of both.”
Elsewhere, hatchery fish have been shown to sometimes displace naturally produced, wild fish.
“In Oregon’s Salmon River estuary, for example, wetland restoration contributed few adult survivors to the local coho salmon population until a decades-old hatchery program also was discontinued,” the study says.
It doesn’t go so far as to suggest the closure of Columbia hatcheries, but instead argues “for designing hatchery releases as experiments to test for density-related effects on salmon consumption, growth, or residence times in estuarine rearing
habitats; and identify any significant behavioral interactions and effects, including whether large pulses of hatchery fish displace NP juveniles from prime rearing areas.
“A better understanding of density effects is needed to determine whether hatchery practices are working in concert with estuary restoration to achieve the survival and life history diversity objectives.”
Though the mouth of the Columbia is about 800 miles south of the city of Ketchikan near the end of the Alaska Panhandle, the river has a strong connection to the 49th state.
Anywhere from a third to nearly half of the Chinook – the big fish Alaskans call “king” – that are caught in the Southeast Alaska commercial troll fishery each year are Columbia fish, according to the Alaska Department of Fish and Game.
The catches vary year to year and depend on when in the season fishing periods are opened, but the Alaska catch of Columbia kings is invariably significant.
The Wild Fish Conservancy last year went to court to try to force a closure of the troll fishery, arguing that “fewer than 3 percent of all Chinook harvested in this Southeast Alaska fishery actually originate from Alaskan rivers. If allowed to fully mature and return home, the other 97 percent would migrate back to rivers from British Columbia to Oregon, feeding the southern resident (killer whales) as the Chinook pass through the whale’s critical foraging areas.”
Meanwhile, pressure has been growing in Alaska for better studies of the interactions between hatchery and wild fish. State Fish and Game officials have dismissed the idea hatchery pink and chum salmon might be linked to declines in sockeye, coho and Chinook stocks around the Gulf of Alaska.
But scientists looking for linger damage from the 1989 Exxon Valdez oil spill in Prince William Sound stumbled on a correlation between returns of hatchery pinks and Copper River sockeye just to the south of the Sound.
When pink returns went up, sockeye returns went down. The Cooper is witnessing a sockeye run of less than 1.5 million sockeye this year, and Sound hatcheries are expecting a bonanza return of close to 38 million pinks.
Statewide, Fish and Game predicts that pinks will account for more than 65 percent of the salmon harvest, and about 40 percent of those pinks will be hatchery fish.
Overall, if the forecast is correct, the Alaska farmed fish – which Alaskan commercial fishermen prefer to call “ranched” – will make up more than 25 percent of the total Alaska salmon harvest.
Thanks to industrial-scale hatcheries largely controlled by commercial fishing interests, Alaska has become a world leader in the production of ranched salmon.
But in Alaska, unlike around the mouth of the Columbia, negative interactions between hatchery pinks and other salmon have been hard to quantify with the exception of the Prince William Sound-Copper River connection.
And as Bill Templin, the director of state fisheries research, likes to say, “correlation is not causation.”
The scientists studying the Columbia found no direct causal links between hatchery fish and fading wild fish, either, but noted the correlations are now so strong it’s time to start a serious search for casual connections.
CORRECTION: The Wild Fish Conservancy was misidentified in an earlier version of this story.