Trapping the Local Steelhead

It’s a gem of an urban creek with an endangered species running right through downtown.   

Biologists Scott Taylor (left) and Aaron Brinkerhoff discuss what's been trapped today.   

Any day—Monday through Sunday, rain or shine—one or more of our biologists will be out on San Mateo Creek with the trout.

The creek flows down to the bay from the Crystal Springs Reservoir through suburbs and downtown San Mateo as well as parts of the Peninsula Watershed. The SFPUC is dedicated to year-round restoration of both creek and critters that live there. We've been releasing small, prescribed amounts of water daily from Lower Crystal Springs Dam into the creek for habitat improvement since 2015, and lead biologist Aaron Brinkerhoff says conditions keep getting better.

These days, Brinkerhoff and team are trapping, then releasing, young so-called “steelhead"--the ones that migrate out to sea. (The rest in the same species are “residents," also known as “rainbow” trout. They'll stay in the fresh water of their birthplace all their lives.)

“This little urban creek is such a gem,” Brinkerhoff says.  “We have an endangered species running right through the neighborhoods."

The trap is set early each spring. That’s when the young steelhead—called smolt—enter certain physical changes that equip them for salt water. They’re now four to eight inches long, they’ve taken on  the silvery hue that distinguishes them from the residents, and they’re moving downstream. The hope is that they’ll survive the three years at sea and return home to spawn.

So any smolt happening into the trap is quickly and gently weighed, measured and implanted with an electronic tag for lifelong tracking. The young captives are kept in cool creek water during the process to minimize any stress before they’re released to continue on their way. “Even a small sample tells us a lot,” Brinkerhoff says. “Over time we’ll be able to see how the population is doing.

“This creek has a unique asset, and that’s our daily flow release. It’s like having a savings account of water.”