Mysteries of fish habitat decoded


Curtis Roegner works in an old U.S. Coast Guard station in Hammond, but he and his colleagues are on a different kind of rescue mission.

Through extensive research in the Columbia River estuary, Roegner and 14 other scientists at the National Oceanic and Atmospheric Administration Point Adams Lab are out to help save the salmon.

One of Roegner's duties is to study the benefits of habitat restoration and to figure out which projects work the best for giving juvenile salmon back the crucial nursery grounds that prepare them for the long journey out to the ocean and back.

Roegner, 47, said salmon have lost about 70 percent of their estuary habitat to development over the years, and scientists aren't sure yet what role habitat restoration plays in the larger recovery effort.

With a doctorate in oceanography from Dalhousie University in Nova Scotia, Canada, and a master's degree in marine science from the College of William and Mary in Virginia, Roegner also uses his expertise to plumb the dynamic saltwater-freshwater interface in the Columbia River estuary.

Dipping a censor into the water from a research boat, he collects data on salinity, chlorophyll, temperature and dissolved oxygen at different depths in the estuary, filling in "baseline" data that could later help scientists determine the impacts of climate change, algae blooms or low-oxygen "dead zones" in the ocean.

"We're trying to find out what it's really like under the water," he said. "What happens when you get low dissolved oxygen on the continental shelf? Does that come into the estuary? ... Are these events increasing or decreasing?"

So far he has detected slightly higher temperatures in some Columbia River waters and masses of a nontoxic red ciliate he calls "red water" that hangs near the surface of the estuary. He's also found that, in fact, low-oxygen water from the ocean is drifting into the Columbia and affecting fish habitat. But figuring out how these things affect the ecosystem is "like a mystery," he said. "It takes a lot of time to solve."

Roegner's work dovetails into other NOAA studies at the mouth of the Columbia to track juvenile salmon survival below Bonneville Dam and predation from cormorants and terns. Every year, a chunk of the Bonneville Power Authority funds for dam mitigation go to support NOAA research in Hammond.

"Everything has to come through the estuary," said Roegner. "Habitat is crucial. Salmon stay in the estuary a lot longer than people think."

Roegner, who did post-doctorate work for the University of Oregon in the Oregon Institute of Marine Biology in Charleston and went on to work for the University of Washington studying Willapa Bay oysters and crab larvae, has been focused on the Columbia River estuary for the past five years at NOAA's Hammond science lab.

He's currently studying the cumulative impacts of habitat-restoration projects in Youngs Bay and Grays River. To document improvements in restored marsh, Roegner tests for fish abundance, tide levels, salinity, vegetation, temperature and dissolved oxygen in the new habitat.

"When you open these places up, the field changes dramatically. We're trying to document all the changes we can and decide how good or bad it is for fish habitat."

At Vera Slough in Youngs Bay, a tide gate replacement has released stagnant water near the new Youngs Bay Bridge and flushed more of the estuary in and out of the marshlands over the past three years. But the impact on salmon has been minimal; while more fish in general now use the marsh, relatively few salmon have returned.

Breaching a dike in Grays River, meanwhile, raised the water levels by about 9 feet and ushered three species of salmon into an area that was previously fish-free.

"It turned a cow pasture into salmon habitat," he said. The next challenge is to figure out how to "kick-start Mother Nature and get a quicker end result."

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