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[October 25, 2008]
Researchers try to find what happened to the salmon
(The Marin Independent Journal Via Acquire Media NewsEdge) Oct. 25--Researcher Robert Abbott sits among mounds of oysters shells at the San Rafael shoreline in hope the shells, along with some high-tech gadgetry, can help re-energize salmon runs in the bay.
The salmon fishery, which has been dwindling over the past few years, hit a low point this spring; to protect the shrinking population, the Pacific Fishery Management Council banned salmon fishing this year off the coast of California.
"We are still trying to figure out what the heck happened to the salmon," said Jerry McEowen of the Marin Rod & Gun
Club, which is helping facilitate research by providing space and access to San Pablo Bay.
Biologists suspect a variety of factors have caused the population crash: changing ocean conditions, toxic pollution, delta water diversions, loss of wetlands and invasive species that compete for food.
All the factors limit the salmon's ability to swim down from the delta, into San Francisco Bay and out to the open ocean, then later return to spawn in the fish's native rivers, creeks or hatcheries.
"They are not getting the right kind of food in the bay," said Abbott, who is with Environ International Corp. and is working on his research with a grant from the National Fish and Wildlife Foundation. "About half have nothing in their stomachs at all when they leave the bay before they go to open sea. This bay used to have a lot of wetlands, and vertical structures and things that produce amphipods, which salmon eat, but they have been largely
Abbott and his team are building artificial reefs from the oyster shells -- donated by Hog Island Oysters in Marshall -- in the water off the Rod & Gun Club in San Rafael to see if fish will be attracted to them.
"We think we will get lots of gobies, and lots of goby larvae on these reefs, which is perfect food for salmon," he said. "We should see amphipods as well settling on these structures. I call it the McDonald's cholesterol delivery system. We want to fatten the fish up."
And how will researchers know if the fish are drawn to the reefs?
Upstream, in hatcheries near Lake Shasta and near the Mokelumne River, workers are inserting small electronic tags in the fish's stomachs. The devices emit an electronic pulse every minute.
Sensors will be placed in the a control area and in the reefs, so when fish swim into the area, they can be monitored.
"We would expect them to go right through the control area, which is mudflats, and then linger at the reef area," Abbott said.
The heavy monitoring will start in December when the salmon begin to make their run.
Fellow researcher Rena Obernolte is holed up in a makeshift lab room -- set up in a Rod & Gun Club smokehouse -- where she peers into a high-powered microscope to see what is growing in the bay.
"We are looking to see how the invertebrate community differs between the mud flat and oyster shell reef," she said. "That is the key to all of this."
If successful, Abbott sees similar reefs being placed around the bay to help the salmon populations. He will share his research with the National Oceanic and Atmospheric Administration, the San Francisco Bay Conservation and Development Commission and others.
"We are desperate to keep what is left of the population," he said.
Read more San Rafael stories at the IJ's San Rafael section.
Contact Mark Prado via e-mail at firstname.lastname@example.org
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