Carp eradication preparation underway in Clear Lake

CLEAR LAKE — You can tell how heavy the huge net is by how the three handlers heave it into the water from their boat just a few feet off shore.

A noisy, motorized spool helps parcel out lengths of the net as they go. It extends up to 1,000 feet.

Lead weights along the bottom edge hold it fast to the lake bottom. Cork buoys on top help it stand up in the water like an arcing wall unfurled shore to shore around an unseen prey, until gradually, painstakingly, the crew starts reeling it back — yanking it over rocks and detritus until whatever is inside is trapped in a tiny space.

So far, the group from Minneapolis-based WSB, a firm experienced with carp management, has merely been testing the waters — trying to figure out where best to operate next fall, when they will come to clear out some of the overabundance of invasive fish populations.

The next time this team comes to town, they hope to capture some of the 10 million pounds of common carp and goldfish that are thriving in Clear Lake and further threatening a struggling native species called Clear Lake hitch.

“This (test run) will save us a lot of shots in the dark when we’re going for real,” Senior WSB Environmental Scientist Jordan Wein said.

Funded by a $177,872 grant from the California Department of Fish and Wildlife, the project is being hosted by the Robinson Rancheria, one of several tribes around the lake working with state and federal agencies and others to try to save the hitch, or “chi,” a culturally important staple food that many fear is on the brink of extinction.

There are multiple challenges to saving the fish — most of them developed over decades of human expansion and activity — and few opportunities to make a short-term impact.

But Robinson Rancheria’s environmental staff hopes eradicating invasive, nonnative carp and goldfish may take some of the pressure off the hitch, in part by reducing competition for food as well as direct predation.

The non-native species “prey mainly on egg and larval stages, but they eat everything,“ said Luis Santana, a fish biologist for the tribe who is participating in the effort.

Carp are a common problem in lakes, reproducing prolifically, thriving in varying temperatures and conditions, and eating a variety of substances in abundance, resulting in over-competition for food and disrupted lake bottoms. They reduce aquatic life and contribute large amounts of phosphorous-rich waste that helps feed algae and further contribute to diminished water quality in which other species can’t survive.

“Carp and gold fish are the last ones standing,” California Department of Fish and Wildlife Fish Biologist Ben Ewing said.

Santana last year tagged 30 carp so that when the fish congregated along the shore for spawning this winter, areas with carp could be detected for the recent feasibility study.

WSB was contracted for the job because of its experience with carp management around the country. It also has identified entities that purchase removed fish for uses like fertilizer and pet food, so the carp don’t go to waste.

But several local residents also are learning the skills of seine fishing, including Stephanie Nix, a water resources technician with Robinson Rancheria, who eagerly boarded the WSB boat for her first try recently.

The crew on Clear Lake caught few fish during its 10-day effort in early February, saving a few dozen for research studies underway by local tribes, a team at University of California, Davis and the U.S. Fish and Wildlife Service.

At one point, it brought up about 40,000 to 50,000 pounds near Cache Creek, most of which were put back in the lake, Santana said.

Karola Kennedy, the tribe’s interim environmental director, said any carp that get removed when the first phase of removal starts in the fall will help the hitch, but the data is not sufficiently refined at this point to know exactly how many fish have to come out to reach a tipping point.

Also, said Santana, “it is a massive lake, and the carp, they do learn, so it won’t work forever.”

You can reach Staff Writer Mary Callahan (she/her) at 707-521-5249 or mary.callahan@pressdemocrat.com. On Twitter @MaryCallahanB.