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Scientists urge Marin County to take steps to protect coho

Aquatic scientists are calling on county supervisors to take action to protect habitat in Marin for the Bay Area’s last remaining wild run of endangered coho salmon, which face extinction.

Wildlife officials are now considering a drastic step to stop Marin coho salmon from disappearing: raising them outside their natural habitat. Later this year juvenile coho salmon could be pulled from Marin creeks and bred in captivity because the species is on the verge of collapse in the county.

Now scientists and environmental organizations, led by the Forest Knolls-based Salmon Protection and Watershed Network, are pressuring the supervisors to enact laws they believe will help protect habitat.

“My concern is not only for the salmon, but everything else that depends on them,” said John McCosker, a California Academy of Sciences senior scientist. “More and more of the ecosystem will be affected. Eagles, osprey, raccoons need their rotting flesh. It goes beyond the coho.”

McCosker, a Mill Valley resident, is one of more than 150 scientists who signed a letter to the supervisors which asks the board to:

– Enact a policy that prohibits removal of streamside native vegetation.

– Implement strict enforcement of violations of illegal new development within 100 feet of streams.

– Require any new development in coho watersheds to not increase the amount of stormwater runoff for the life of the project.

– Close loopholes in the stream conservation area ordinance that
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allow new construction in the zone and a net loss of riparian habitat.

Supervisor Hal Brown said Tuesday he had not seen the letter, but he said the county has addressed some of the issues.

“We are doing everything possible that we can,” Brown said. “At the same time we only have so many resources for enforcement. We know there are people who build illegally.”

Brown added that for older structures, “we do want to allow for some flexibility” for property owners.

Last month a controversial proposal prohibiting cutting trees and brush near creeks in the San Geronimo Valley was sent back to the drawing board as county supervisors called for a compromise aimed at preserving salmon habitat while accommodating homeowners.

Although the board took no formal vote, supervisors in effect rejected a strict regulation proposed by planning commissioners and instructed staff to return with a more modest proposal that can be used as a model for a countywide creekside program.

Peter Moyle, professor of wildlife, fish, and conservation biology at the University of California at Davis, said it’s critical steps be taken to protect Marin and other nearby coho populations.

“The lack of habitat protections in the headwaters of the Lagunitas watershed for this wild run of salmon could impact the recovery status of extirpated populations along the entire central California coast,” said Moyle, who also signed the letter.

That’s because Marin’s Lagunitas watershed has one of the largest remaining populations of wild coho salmon in Northern California, but now the fish have virtually vanished. In the past three years the number of fish returning to streams in its range, between Mendocino and Santa Cruz, has also taken a precipitous drop.

That the species – known as the Central California Coast coho salmon – is in trouble is not a surprise. The federal government listed the species as threatened in October 1996 and in June 2005 it was re-listed as endangered.

Coho salmon have a three-year life cycle in which they hatch, live in creeks for a year and go to sea for two years before returning to their birth sites.

In the 1940s, there was a statewide peak of 500,000 coho. But today’s native coho population is 1 percent of that – a decline caused primarily by a loss of free-flowing creeks and rivers that have been affected by development, culverts, dams and other obstacles. Development along creeks fills creekbeds with sediment, limiting oxygen for fish. Coho are gone from 90 percent of California streams that once supported the species.

“When I first came to Mill Valley in 1973 the population was a lot stronger, it was a remarkable sight,” McCosker said. “Now their populations have gone down, down, down and they are barely surviving.”