San Jose residents are being asked to keep an eye out for people setting illegal fish traps in local waterways after city workers and South Bay Clean Creeks Coalition volunteers recently broke up several found in the Guadalupe River.

The traps were discovered about two weeks ago under the Julian Street bridge and farther south near Virginia and Willow streets. The fish traps are built out of large items like river rock, which block the stream so fish become penned into a shallow pool of water away from their migratory path. That makes it easy for poachers to nab the fish from the stream. It can also interfere with wildlife research and fish repopulation efforts such as those supported by the coalition.

All of the structures were promptly removed by coalition volunteers and the San Jose Conservation Corps, but coalition founder Steve Holmes told the Resident it wasn’t the first time they’ve appeared. Several illegal traps were also found last month, and they’ve been discovered in the same areas stretching back at least several years.

“We’d seen crude traps along the waterways when they were made out of nets or barriers of shopping carts,” Holmes said.

Fish trapping is always problematic for game wardens and other wildlife professionals, and the new traps are even more sophisticated.

“One on Virginia Street…that one was really kind of well-designed. You had these low walls that allowed the fish to jump over, but there’s no stream,” he said. “There’s a wall and water seeping through it but no direction to follow. They become disoriented. People just come in and poach the fish.”

Holmes said there’s a “constant vigil to keep people from doing this,” noting more than 30 people including volunteers and game wardens now monitor the Guadalupe and all its tributaries for signs of unlawful activity. Signs reminding people to not fish in the river were added as an extra measure.

The California Department of Fish and Wildlife is “very aware of the situation,” according to spokesman Peter Tira, who said the dams sometimes are built for other reasons besides capturing fish.

“We found that the homeless will build dam structures to back up the creek, but they’re probably built for a variety of reasons including places to bathe, clean, do dishes and to cross the creek,” Tira said. “We do believe there’s cases where they may be used to poach fish, but it’s not just for fish. We believe it’s a combination of things going on.”

Several fish species that inhabit the Guadalupe River, including Chinook salmon, are predominantly strays from a hatchery in the Central Valley. A small population of Central California Coast steelhead trout, which are listed as threatened under the federal Endangered Species Act, are particularly vulnerable, according to Tira.

“They’re not in good shape; the last adult confirmed steelhead sighting was before 2013,” he said. “It’s significant because we want to see adult fish, because it means that they have returned to spawn or have moved up and down the river. Those are the fish that reproduce, so we like to see adults.”

People caught fishing without a license usually get hit with a base fine plus state and county penalty fees. The minimum fine is usually $485 but could be much more if other offenses are committed, such as taking salmon from spawning areas.

Tira said there are “special fishing regulations specific to the Guadalupe River that govern the fishing season,” which ended last month. Those rules spell out how many and which kinds of fish can be caught, and specify that only artificial lures and barbless hooks may be used.

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Anyone who sees illegal fishing is asked to call the California Department of Fish and Wildlife’s “Cal-Tip” hotline at 888-334-2258.