Salmon Wetlands Slipping Away

July 9, 2001 -- Ayesha Gray sits sheathed in chest waders and heavy boots — perfect gear for slogging through the water-filled channels of central Oregon's SalmonRiver estuary.

Despite the inconvenience of working in waist-deep mud, Gray feelsprivileged to be studying the estuary's wetlands. Throughout the PacificNorthwest, wetland habitats in estuaries have been destroyed or degraded.

This is bad news for juvenile salmon, which rely on these marshyhabitats to make the transition from freshwater to ocean-dwellinglifestyles.

"People once thought of wetlands as worthless wastelands," says Gray, adoctoral student in fisheries at the University of Washington in Seattle.

But for salmon, whose stocks have been recently added to the federalEndangered Species list, nothing could be farther from the truth.

Learning Life Skills

Different species of salmon rely on estuarine wetlands to varying degrees.While some spend only two or three weeks of their youth in the estuary,others may spend up to four months in the same locales before heading out tosea.

Estuaries are important to all ocean-going salmon, says Dan Bottom of theNational Marine Fisheries Service. The water in estuaries is saltier than infreshwater rivers or lakes but not as salty as the ocean, he says. The Salmon River estuary serves as a staging area where salmon can graduallyadjust to more briny ocean conditions.

The estuaries offer salmon more than a transition environment, says CharlesSimenstad, a research associate professor at the University of Washington,who, with Gray and Bottom, has been studying the Salmon River estuary since1997.

"For one thing, the murky waters of estuaries make it harder for blue heron,bald eagles and other salmon-eating predators to spot the juvenile fish," heexplains.

With estuaries in decline, it's not surprising the species and typesof salmon that are most wetland-dependent are also the most endangered. Lastyear, the federal government conferred protection under the EndangeredSpecies Act to two of these — the Hood Canal summer chum and Puget Soundfall chinook salmon of Washington state.

Eat, Eat, Eat

Gray's studies focus on the estuary's role in the salmon's feedingand growth. "For juvenile salmon, their job is to eat," she says. "Eat andeat, just as much as you can … and don't get eaten."

The estuary's wetlands are fantastic foraging grounds, filled with aquaticinsects and small shrimp-like amphipods for the young fish to chow down.

In these food-rich habitats, juvenile salmon can gain 6 percent to 10 percent oftheir body weight per day. As Simenstad points out, "That's the equivalent of one of us putting on 15pounds overnight."

Salmon that linger in the estuaries may bemore likely to reach adulthood and spawn, producing the next generation offish.

Threatened Wetlands

Despite their value to salmon, estuarine wetlands have declined at the hands of humans. Across the Northwest, from 50 percent to 90percent of these natural habitats have been destroyed or degraded as aresult of diking, draining, or paving over to make way for agriculture orurbanization.

Now with help from the U.S. Forest Service and Oregon and Washington SeaGrant programs, the researchers are looking at ways to recover some ofthese lost salmon habitats. Within the Salmon River estuary, they've stakedout three wetlands where historic dikes have been removed and where nature is already repairing itself.

Combined, the three wetlands are a living laboratory in which theresearchers can watch how salmon respond to the wetlands in different stagesof recovery. They can track the salmon's movements through the differentparts of the estuary, study what these youngsters eat and measure how fastthey grow.

The researchers believe that a better understanding of this critical time inthe fish's life history will help guide future efforts to restore estuarinewetlands. And, perhaps, save the salmon that depend on them.

"Previous efforts to save salmon have focused on the open ocean or thefreshwater rivers of their birth," says Simenstad. "But they've often failedto consider the estuaries important links between the two domains."

Next week: the researchers explain how the fates of salmon and wetlands areentwined.