A bevy of road-weary salmon filled the Mokelumne River in the Central Valley town of Clements, having made the long upstream journey from the Pacific Ocean, now doggedly intent on returning to their place of birth to complete their final act of life: spawning.
Jose Setka looked down from a metal footbridge as fish swarmed underneath, leaping up a small waterfall and into the Mokelumne River Fish Hatchery.
“When I first started working in the early 90s, if we had 5,000 fish come back to the river, we were ecstatic,” said Setka, the East Bay Municipal Utility District’s Director of Fisheries and Wildlife.
Through two decades of research and modifications to the river, the hatchery has become a rare success story in the fight to restore beleaguered salmon populations. The facility is now a destination for salmon, these days averaging 10,000 returning fall run chinook, or king salmon, a year.
Last year the hatchery set its new high point with 20,000 salmon returning to the facility. Setka said this year’s numbers were slightly below last year’s — somewhere above 15,000 — yet the results were still encouraging given the challenges.
“Another thing to recognize is a lot of these fish were born essentially during the drought years where conditions not only in the Mokelumne but especially in the Delta were not good,” Setka said.
Over the last 20 years, the hatchery has continually tweaked every aspect of its operation: adding gravel to the river to create better spawning habitat; using pulse releases of water to entice fish to head up river, and focusing on releasing juvenile hatchery fish down river in the Delta to avoid some of the hazards that threaten young fish as they journey to the ocean.
“One of the great things about fish coming out of this hatchery is they tend to be bigger and stronger,” said John McManus, Director of the Golden Gate Salmon Association. “When they come out they’re really big and strong and because of that they survive at much higher rates.”
Amid four other Central Valley fish hatcheries, Mokelumne has emerged as the biggest success story. During the last salmon fishing season, fish from the hatchery accounted for one-third of all recreational fish caught, and 20 percent of the commercial catch.
“Some of the other rivers in the area aren’t doing quite as well,” said Jay Rowan of the California Dept. of Fish and Wildlife. “So having some fish out in the ocean that people can catching commercially or recreationally has been a huge help.”
While some of the fish will spawn in the gravel of the river waters just outside the hatchery, most will navigate up into the facility where they become part of an artificial spawning assembly line. The milk and eggs are extracted from the males and females and artificially inseminated. The eggs are stored in the facility until they hatch. Newly hatched fish are raised in long metal channels before they’re released in the Delta in May. The hatchery has also raised fish in net pens in Half Moon Bay to improve their chances of survival even further.
Setka looked like a proud father beaming down from the footbridge as fish clamored below, instinctively pushing on toward the facility where they were conceived three years earlier.
Setka watch the scene as drops of rain began to pelt his face.
“It is an incredible success story,” he said.