Marin County biologists have obtained a new antenna they say will bolster recovery efforts for the critically endangered and largest remaining population of Central California Coast coho salmon.
Using a system of radio tags and electrical fields, the equipment is expected to give researchers more accurate counts of coho salmon that will return to Lagunitas Creek to spawn beginning later this month as well as the young salmon leaving the creek and entering the ocean in the spring.
“The real research question we’re interested in is we want to know which fish in the watershed are surviving the best,” said Eric Ettlinger, an aquatic ecologist with the Marin Municipal Water District. “We really want to figure out what allows them to survive, and can we improve habitat conditions elsewhere to allow fish throughout the watershed to survive better.”
Where once more than 10,000 coho salmon would make the journey from Tomales Bay up Lagunitas Creek toward Mount Tamalpais, the population has since become critically endangered. The main threats since the mid-20th century have been the dams blocking tributaries; development blocking vital flood plains that act as a safe harbor from swift storm flows; the introduction of invasive species; and ocean fishing.
Researchers now find an average of about 250 salmon egg nests, known as redds, in the watershed each year, far below the federal target of 1,600 redds needed to remove the endangered status. Last season, researchers recorded the lowest counts of salmon redds in 12 years.
A 2017 report by the University of California at Davis report found the Lagunitas coho were at high risk of extinction in the next 50 years without “significantly increased intervention and protection of watersheds.”
Agencies and conservation groups such as the Salmon Protection and Watershed Network, or SPAWN, have been working to reverse this damage and restore habitats to give the species a chance at survival.
“They’re a keystone species and critical to not only their own survival but the survival of the whole ecosystem,” said Todd Steiner, the executive director of SPAWN. “They may very well be extinct if we hadn’t been doing the work that we have been doing.”
The new fish counting antenna installed near the mouth of Lagunitas Creek aims to make the most of this often expensive restoration work.
The Marin Municipal Water District has been tracking the movements of coho salmon for the last eight years using 12-millimeter radio tags that biologists surgically insert into the young fish while they’re rearing in the creek and its various tributaries.
Using the antenna, Ettlinger has been able to track which of the young salmon survive the year-and-a-half rearing period in freshwater and make it out to the ocean. The antenna creates an electrical field and sends out a unique code whenever a tagged fish passes by. Researchers are also alerted when these young fish survive the perilous ocean waters and return to the creek as adults to spawn another year-and-a-half later.
But the old antenna, which Ettlinger designed himself, had its problems. Standing upright, it was prone to catching sticks and other debris during floods. It also wasn’t very sensitive, Ettlinger said.
“A lot of the fish could swim through it without being detected,” Ettlinger said.
Using $23,000 obtained with help from Trout Unlimited’s Golden Gate Chapter, the Marin Agricultural Land Trust and Marin County, the water district purchased an upgraded antenna that addresses past issues and provide researchers better data on which fish are surviving.
Researchers are hoping for an average number of spawners to return this year based on a large number of young salmon, or smolts, that entered the ocean in the spring of 2019.
“I’m having a hard time predicting what we will get this year for a coho run, but it should be better than the disastrous run of last year,” Ettlinger said, referring to the 2019-2020 redd count of only 44 redds.
But fish monitors have a new hurdle to deal with this year in the form of the coronavirus pandemic. Coho salmon researchers with the National Park Service are being particularly affected after losing about $130,000 in funding used for monitoring Redwood Creek.
“I’m looking at trying to do the same amount of work with half the financial resources,” said Michael Reichmuth, a park service fishery biologist who leads the monitoring efforts. “I do realize that everyone is going through this stuff right now, so I’m not alone in this.”
About $100,000 of the loss was the result of the California Department of Fish and Wildlife deciding not to provide its annual grant funding for the Redwood Creek monitoring. The department cited the need to focus its reduced funding on other waterways, according to Reichmuth.
Fish monitors will also be unable to travel in shuttles together to various monitoring sites along Redwood Creek because of the coronavirus. Instead, they’ll have to trek as much as 10 miles to and from various spots along the creek.
“It can be physically draining, but it is a benefit to us that luckily since the creeks are in the parks, there is a pretty good network of trail systems that we have had at our disposal,” Reichmuth said.
