Salmon returning to Marin creeks

By November 29, 2004Uncategorized

Federally protected coho salmon are slowly but surely making their way back to the creeks of Marin to spawn with a little help from locals working to re-establish populations, which have winnowed over the years.

“The overall trend has been an increase in population in coho but there have been variations from year to year,” said Greg Andrew, fisheries biologist with the Marin Municipal Water District, which manages much of the Lagunitas Creek watershed. “The best way to describe the coho population is stable, but tenuous.”

In the 1940s, Lagunitas Creek helped contribute to a statewide historic high of 500,000 coho. At Lagunitas Creek, the largest coho salmon in state history – 22 pounds and 36 inches long – was caught in January 1959.

But today’s salmon population is 1 percent of that – a decline precipitated primarily by a loss of free-flowing creeks and rivers that have been impacted by development, culverts, dams and other obstacles. Coho are listed as a threatened species by the federal government and endangered by the state.

Still, Lagunitas Creek and its tributaries are among the state’s prime coho salmon spawning grounds, and host of groups are working to keep the species stable.

Counts by the MMWD of redds – gravel nests where fish lay eggs – has been strong in recent years and efforts to buoy the coho may be part of the reason, researchers say. The water district spends about $460,000 annually on its fisheries programs.

The water district, for example, has placed logs – which are secured with wire and boulders – in sections of the creek to create pools. The pools help protect the fish from rushing waters during heavy storms and create a place for the coho to thrive during dry summers. The National Park Service has done similar work in Redwood Creek in West Marin.

“Placing of these woody debris are tiny steps that improve conditions and each year bring a few more fish,” said researcher Jerry Smith, a San Jose State University professor who teaches fisheries management and conservation biology. He has studied juvenile coho in Redwood Creek for the last decade. “Those pools are important during storm years so the fish and eggs are not swept away.”

The coho spawn in the Lagunitas watershed each winter after the two-foot fish, which weigh up to 12 pounds, leave the ocean and travel miles up local streams to lay their eggs, riding in on the coattails of large storms as Marin’s creeks swell.

They arrive as red, shimmering fish ready to spawn a new generation. Spawning continues into January.

Young fry who are born will repeat the same journey, if they are lucky enough to survive predation, heavy rains, dry summers or any other number of risks, which are many and sometimes unexpected. Coho have been preyed on by river otters who are coming up and eating salmon on Lagunitas Creek the last two years.

The 2- to 6-inch fry emerge in the creek and stay about 18 months, then head out to the open ocean and spend another 18 months before they come back to the creeks, spawn and then die – a three-year life cycle.

From his work in Redwood Creek, Smith is optimistic about the future of the coho.

“All of the classes or coho are doing well and have been able to rebound from disasters such as heavy rains and dry summers,” he said. “But coho are a very particular species and they don’t do well in fluctuating environments.”

And some of the coho environment can never fully be replenished, Smith noted.

Redwood Creek, for example, is affected as the community of Muir Beach pulls groundwater that would otherwise end up in the creek, lowering water levels, Smith said.

Also, a body of water known as the Big Lagoon at the mouth of Redwood Creek once was a large lake, allowing coho a place to stop and rest, increasing their chances for survival.

But in the 1950s, the 12-acre fresh water lagoon – which had another 13 acres of surrounding wetlands – started to disappear, choked to death by fill and levees put in by ranchers so the area could be used for cattle grazing. Sediment from development and the parking lot at Muir Beach further damaged the resource. Today, it resembles a meadow, covered with grasses and trees.

As the lagoon was lost to farming it disappeared, and so did many coho. The National Park Service now has plans to restore the lagoon.

“It will never be back to what it was, but it will help the fish thrive in good, wet years and protect them in dry years,” Smith said. “All these things help stabilize the population.”

Last week, members of SPAWN – the Salmon Protection and Watershed Network – were at Roy’s Pools along San Geronimo Creek planting willow, huckleberries and honeysuckles to create shade for the coho.

“These pools were pretty much exposed to sunlight and what that does is promote the growth of algae and it also dries out the pools,” said Paola Bouley, aSPAWN watershed biologist. “We are here to create a shady environment.”

San Geronimo Creek is a main tributary to Lagunitas Creek.

“These tributaries are really important spawning habitat for salmon, and before people didn’t realize that,” said Bouley, as she teetered on the edge of a culvert, planting a honeysuckle.

SPAWN helps coho in other ways. During the summer they pluck juvenile coho from drying creeks and get them into wetter areas.

“We have seen a large-scale decline, but it relatively stable now, with a population of about 500 spawners in the Lagunitas watershed since the mid-1990s, and it’s the largest wild coho run in California,” Bouley said. “Even though it’s the largest it is very vulnerable because it is a small population and very isolated.”

The Marin County Resource Conservation District, Trout Unlimited and others have also been involved in efforts to help save coho as well.

“The main goal is to maintain what we have and to protect what we have,” Bouley said. “It will take a little longer to see the effects of what we are doing, but these efforts have helped stabilize the population.”