Rainbow trout in Alameda Creek signals return of normal migration

Local conservationists focused on restoring Alameda Creek as a habitat for steelhead trout and other fish species who carry out most of their lives in ocean waters before migrating to inland waterways to spawn are celebrating what they call a milestone after finding a young fish they have been seeking to see accommodated in the local tributary to San Francisco Bay last month.

A juvenile rainbow trout was found in the creek by Alameda County Water District and San Francisco Public Utilities Commission, who issued a joint statement on April 24 along with the Alameda Creek Alliance.

“We’ve made incredible progress building fish migration infrastructure in the lower urban portion of our watershed, allowing spawning adult salmon and steelhead to swim upstream to reach good habitat in Niles Canyon and the upper watershed toward Sunol Regional Wilderness,” Jeff Miller, director of the alliance, said in a statement. “But the successful downstream migration of juvenile fish is just as critical; it’s gratifying to be able to document some of our trout moving toward the Bay to complete their dramatic life cycle.”

The young rainbow trout’s appearance in the creek’s lower watershed means that things are going as planned for conservationists at the alliance, as well as ACWD and SFPUC officials, who have collaborated for more than 20 years to restore the creek as a viable habitat for adult steelhead to spawn, and for juvenile rainbow trout who result to migrate through in order to carry out the majority of their adult lives in the open ocean.

Tagged juvenile trout were first detected in the upper watershed in October, with the completion of a “fish ladder” that enables fish to navigate through a previously impenetrable barrier to the open bay being completed in December. This means that in addition to being born and growing in the creek, the juvenile fish can return as adult steelhead for their own spawning process.

SFPUC biologist Brian Sak said that while it was gratifying to see results from the decades of work aimed at restoring the creek as a spawning habitat for steelhead, conservation efforts such as those leading up to the milestone marked last month are necessarily long, painstaking processes, with SFPUC having been monitoring steelhead — or the lack thereof — in the creek since 1998.

“We’ve always expected that some of the resident rainbow trout in the upper watershed that have been shown to be directly related to the system’s historic steelhead make it out to the Bay and ocean when the conditions are just right,” Sak said. “But we have been hoping that reservoir water releases designed to improve spawning and rearing, along with passage improvements, would make things easier for fish.”

“Having confirmation for the first time that trout from upstream are making it downstream to at least Fremont is wonderful news for the countless people that have worked so hard for the shared goal of bringing steelhead back to Alameda Creek,” he added.

Prior to the most recent fish ladder installed in December, the first fish ladder was installed in 2019 slightly upstream from the current one, with both being aimed at giving steelhead an opportunity to bypass flood control and water supply infrastructure that was blocking them from traveling up the creek.

In total, the ongoing Alameda Creek Fish Passage Improvements Program is set to cost $80 million, with more than $30 million in grant funding secured.

“This epic event of fish passage demonstrates how communities and stakeholders can come together with a united goal of improving such an important resource,” ACWD Board President Paul Sethy said. “It is wonderful to see this positive first sign, and it shows that even in an urban environment we can have natural beauty and functioning ecosystems — right here in our own backyard.”