In a possible sign of the tension around the issue — or maybe a simple act of vandalism -- someone arrived on the banks of San Geronimo Creek last month and ripped out salmon-monitoring equipment used by Salmon Protection and Watershed Network, the group that has led the campaign to save the coho that still come back to the local creeks to spawn every year. The group — yes, it goes by the moniker SPAWN — uploaded this video, showing someone ripping the monitoring station out of the creek:

The fate of coho salmon in the Marin streams could have ramifications far beyond the North Bay. What happens to coho salmon there could affect the species throughout North America, said Eric Ettlinger, an aquatic ecologist at the Marin Municipal Water District.

“It’s the southernmost stable population in North America,” he said. “It’s very important for California because our fish likely have adaptations to live where the water is warmer than it is farther north.”

As the climate gets warmer, the Marin fish might share these adaptations with coho farther north, providing a measure of protection for the species.

But the Marin coho have gone through a tough time in recent decades. Though biologists did not keep a close count until the 1990s, they estimate that thousands spawned each year in the Lagunitas watershed until half a century ago.

From the winter of 1995-1996, biologists have estimated the population at about 500 adults. Then in 2008, the number dropped to about 50 adults, low enough that the population might start inbreeding. “A population that stays at that level has a severe risk of extinction,” said Ettlinger.

Dams that provide much of the water for Marin County cut off about half of the salmon’s habitat, Ettlinger said. But he added that the construction of buildings and roads, the introduction of nonnative plants and the removal of wood from streambeds also played a role.

Environmentalists want a buffer along the streams to protect plants that shade the water, provide food for the salmon, prevent erosion and runoff, and slow currents that can harm baby salmon.

In its current draft, the ordinance doesn't go far enough, said SPAWN Executive Director Todd Steiner. "The ordinance creates a 100-foot streamside buffer but has exemptions that allow anyone to develop within it," he said.

For example, it exempts ephemeral streams — those that dry up in the summer — unless they have vegetation of the type that lives on streams. And it exempts additions to buildings if the additions are 500 square feet or less.

On May 23, SPAWN released a letter from 140 scientists calling for a more restrictive ordinance.

On the other side of the debate, the San Geronimo Valley Stewards, a group of property owners, said the ordinance goes too far.

Niz Brown, the group's treasurer, says she owns three pieces of property on which development would not be possible under the ordinance because it is so restrictive.

It makes sense to exempt ephemeral streams because they don't have fish in them, she said. "They're really not streams, they're ditches," said Brown.

She said salmon populations are rebounding, so the protections aren’t necessary. She pointed out that the Marin coho population has come back since 2009.

Scientists estimate the number of adult salmon by doubling the number of redds, or nests. (Courtesy of the Marin Municipal Water District)

In the winter of 2012-2013, biologists estimated there were about 486 adults. Ettlinger said changes in ocean conditions seem to have played an important part in the recent fall and rise.

But the latest count still falls well short of the 1,300 that would be required to change the fish’s status from “endangered” to “threatened,” and is a small fraction of the 2,600 that would classify them as “recovered,” said Charlotte Ambrose, recovery coordinator for the National Marine Fisheries Service in Santa Rosa.

And Ettlinger said ephemeral streams really are important to salmon. Unlike artificial ditches, ephemeral streams flow into larger streams, affecting the water quality. Even when they appear dry, Steiner said, water flows beneath the surface.

That brings us back to the banks of a creek you can see flowing all year round, San Geronimo, the scene of last month's vandalism.

The person shown on the 31-second SPAWN video — you can't see much about who it is, though the individual appears to be Caucasian, barefoot and have jeans rolled up—destroys a monitoring station consisting of a net that funnels the fish into a box where researchers count and examine them before releasing them back into the water.

SPAWN's Todd Steiner said some of the equipment belonged to the California Department of Fish and Wildlife and some to his group.

SPAWN is offering $500 for information leading to the conviction of the culprit. The organization requested that anyone with useful information contact Andy Harris at andy@tirn.net or call the SPAWN office at (415) 663-8590.

San Geronimo Valley StewardsSan Geronimo Valley Stewards

In Marin County, a Battle Between Salmon Survival and Property Rights