Coho salmon vanishing from Russian River

February 9, 2009 7:59:34 PM PST
The North Bay streams and creeks that feed the Russian River were once prime breeding grounds for one of California's prized fish. But overfishing, pollution, low water levels and dams have pushed Coho salmon to the edge of extinction.

You're not likely to see Coho salmon in Sonoma County's Russian River any time soon.

The tubs may be the Coho salmon's last hope. A captive breeding program at the Warm Springs Hatchery is trying to pull the fish from the verge of extinction.

"We decided that we had to intervene before the last wild fish disappears," said Manfred Kittle from California Fish & Game Department.

A breeding program was established in 2001 to bring the Coho salmon back to the Russian River. It is a collaboration between local, state and federal agencies and non-governmental organizations.

"So what we do, is catch wild fingerlings, bring them into the hatchery, we grow them to adulthood - we spawn them and the offspring are released back into the same stream where the parents came from," said Kittle.

"Some of those offspring will be kept at the hatchery and thus become captive breed stock and will be used for future spawning efforts," said biologist Ben White.

White heads up the salmon breeding program for the Pacific States Marine Fisheries Commission.

"In the wild they choose when to spawn, who to spawn with, and where to spawn, here in captivity it all falls on us," said White.

Each fish is fitted with a tag so it can be identified by scanning. This is a hands on job. Every week, biologists check the fish to see if they are ready to breed. Females are given a firmness rating between one and five.

"One being the tightest and the firmest, and essentially the farthest away from spawning and five -- a five being really soft, I call it like jelly soft meaning that she's ready to go, probably within a week," said White.

Their color will also change when they are ready to spawn.

"Prior to spawning, this whole belly of the fish will be dark almost a really dark grey," said White.

An ultra sound determines whether the female's eggs are mature. Numbers are attached to fish to make them easier to identify. Each salmon is carefully cataloged in order to maintain the greatest genetic diversity.

When they are ready these salmon are transported to holding tanks for a couple days until they are ready to breed.

When they are ready, biologists carefully choose the males, and check to make sure they're viable mates. When the eggs are ready, they are extracted from the females.

"So I get the eggs out of her by just applying pressure on her ventral surface," said White.

Each female salmon can only lay eggs once, and dies after she spawns. So biologists are very careful to make sure they collect every single egg.

"I would say the average is between one and three thousand eggs," said White.

Detailed records are taken on each fish. Each female's eggs are separated and fertilized by four different males to ensure genetic diversity. They are sorted into trays where they incubate until they hatch.

When the fish are old enough, they will be released back into the wild. But their odds of returning to breed are not good. About 6,000 juveniles were released in 2004, and only a handful returned.

"Every year though you can count the number on one hand - so it's been few and far between so far, but every year we expect more and more to come back, said White.

And with each little fish that returns the co-ho salmon get one more chance to keep their species alive.

If drought conditions improve, the Department of Fish and Game hopes to release 60,000 to 90,000 Coho salmon this year.

But only one percent of them are expected to eventually return and spawn.