The annual ocean sojourn for endangered coho salmon and steelhead trout made an unexpected pit stop in West Marin County’s San Geronimo creek this week, courtesy of a strange looking trap. Fortunately for the fish — the trap was manned by researchers from the advocacy group Turtle Island Restoration Network — whose loyalty is solidly on the side of the fish.
“We are counting the fish that are migrating back to the ocean,” explained Turtle Island director Todd Steiner.
The creek, which is part of the Lagunitas Watershed, represents one of California’s last wild spawning grounds for coho salmon. For three months during late-winter/early spring of every year, the group sets up a trap along the creek to funnel fish into a pen as they make their way from freshwater to ocean. The traps are emptied daily — with researchers weighing, measuring and taking a scale sample from each fish, before releasing them downstream.
“They take scale swabs,” said Catie Clune, Turtle Island’s education director. “We’re able to age them through that much like a tree ring.”
According to federal statistics, the watershed once was home to 4,000 coho salmon. But through the years their numbers have dropped to dire levels. The majority of the fish turning up in the group’s traps this week were steelhead and a strange eel-like creature called a lamprey.
“So we’re down to a couple hundred fish,” said Steiner of the coho, “in one of the best streams in the state.”
In the first few weeks of the trapping, the group collected 15 coho salmon and 141 steelhead -- distressing numbers for researchers who are hoping to restore the salmon population.
“This is the worst season ever maybe for coho,” offered Turtle Island researcher Alex Hearn.
Steiner blames development along the creeks for contributing to the salmon’s decline. The group is pushing for county legislation that would ban further development on the creek. Steiner said the drought may also be playing a part by stranding outgoing fish in small pools on the creek bed during summer, where they become vulnerable to hungry animals.
Newly hatched coho spend a year-and-a-half in the creek system before heading out to ocean where they’ll remain for a year before returning to their birthplace to spawn and die. Steiner said the annual fish survival numbers give researchers a good vantage point to gauge the health of the creek system.
“I hope what we’re not doing is studying a species as it goes extinct,” Steiner said.