For years, their path was blocked by dams and flood protection structures. After years of work and the creation of a path, the steelhead trout have now returned.

For the past 25 years, the Alameda Creek Fisheries Restoration Workgroup, a coalition of public agencies and nonprofit organizations, has worked to remove barriers to migration and provide fish access to San Francisco Bay and the Pacific Ocean.

And for 15 years, San Francisco Public Utilities Commission biologist Randy Renn has been part of this coalition and this effort.

“It was certainly a lot of work, but it was rewarding,” Renn said of the years of work. “This is our high-water fish trap, as you can see, it's aimed downstream to catch the fish swimming upstream.”

Between 2015 and 2023, Renn and his team of biologists have observed, caught and released about 300 fish. This year alone, they have seen their biggest resurgence, tagging nearly 2,600 steelhead trout.

“Steelhead trout are an indicator species and we are seeing an increase in fish populations in this watershed. This tells us that our watershed is healthy,” Renn said.

The reintroduction of steelhead trout will improve the overall health of the stream and the surrounding watershed.

A healthy watershed ensures high-quality water. The water system serves approximately 2.7 million customers.

Renn is in Sunol almost every day during fish-watching season, including weekends and holidays, to process the trout. Each fish is anesthetized in that water, then they implant a transponder, weigh and measure the fish, then take a scale and tissue sample.

The transponder acts as a fast-track. When a fish passes certain antennas placed along the stream, this is registered.

One of the antennas is in Fremont, where people can see the box light up when a fish with a transponder moves through it.

“We have already recorded 50 unique tags of our migratory fish this year, compared to just one tag detection last year,” said Leonard Ash, Alameda County Water District manager.

Ash explained that two small dams east of Fremont were removed and fish ladders were added to make it easier for fish to move through the water system.

“We need to provide safe passage for fish swimming upstream or downstream,” Ash said.

Renn is excited about the improvement and that different agencies are working together to make it possible.

“Everyone is here for the same reason: the fish and the health of the watershed,” Renn said.

So far, they have not been able to track the entire life cycle of a steelhead trout, but Renn is confident they will be able to do so in the next few years.

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