DFW helping to re-establish fishery in southern stretches of river by planting broodstock
Blackrock Fish Hatchery broodstock, those big trout used for spawning to propagate future generations, are being released in the Lower Owens River.
Last week marked the second large-scale release of the hatchery’s broodstock in as many months—and officials from the Department of Fish and Wildlife said there is going to be at least one more release in the coming month.
DFW Environmental Biologist James Erdman said he and other DFW biologists wanted to let all anglers know that the big broodstock fish from the ponds at the Black Rock Hatchery are now up for grabs.
The fish have been planted in the Owens River below Tinnemaha Reservoir, with one release done this past week and a previous one on April 22.
The fish are mostly browns and rainbows between three and five pounds each. Last week, Erdman said, the DFW released 222 fish in a load that weighed 1,000 pounds.
In April, the hatchery released 317 fish with a total weight of 950 pounds.
The fish have an average weight of three to four-and-a-half pounds.
“These super-catchable and trophy fish are available to be caught by anyone with a valid fishing license,” Erdman said.
The DFW is releasing the broodstock for two reasons.
The first, Erdman said, is because the invasive New Zealand mudsnail, which has infested the Owens River for about a decade, has been identified near the broodstock ponds and although Erdman said the big fish have not tested positive for carrying the snail, he’s taking no chances.
The snail can “hitch a ride” on trout once the waters are contaminated. When a trout eats the larvae of the snail, it then excretes them.
The larvae can then attach to the bottom of the waterway and, Erdman said, one snail could asexually produce a million snails.
Although the broodstock fish released into the Owens River were not found to be contaminated with the snail, Erdman said getting rid of the broodstock was a “pre-emptive strike,” since the broodstock ponds are located adjacent to the river.
“We’re clearing the fish out to ensure that the mudsnails from the river don’t get into the hatchery operation,” he said.
The Blackrock Hatcheries runs, in contrast, are clean; well- and spring-fed from water sources that are not infested with the invasive species—something that Erdman and the rest of the agency will do almost anything to maintain.
The second reason, he added, is because local hatcheries are switching from their traditional rearing of rainbows and browns to the sterile triploid trout, which grow faster because they don’t use any energy on reproductive functions.
The benefit of releasing the trout is also two-fold.
By stocking the Lower Owens with the broodstock, Erdman said, anglers fishing waters south of Tinnemaha Reservoir will have a better chance of landing a lunker. He said he has already heard reports of residents catching some of the big fish on the Lower Owens.
He also said the broodstock, as breeders, will help get the fishery on the river established, as the river reclaims its original course. The river was dry from the mid-1900s until 2006 due to the Los Angeles Department of Water and Power diverting water into the Los Angeles Aqueduct.
The river was “rewatered” at a lower-than-original-average-flow but at a flow that could sustain a fishery—after Inyo County Superior Court Judge Lee Cooper ordered DWP to rewater the river.
The rewatering of the river has been an experiment in bringing back a section of the river that once was a thriving fishery.
Aside from the benefit of helping to establish a healthy trout population in the river, Erdman said the DFW selected the Lower Owens for broodstock stocking because of its proximity to the hatchery.
“Because we electrically shocked them, the fish get very stressed out, so we try to get them as quickly as we can to the water, and the Lower Owens is literally right there,” he said.
Blackrock will continue to produce trout after the remaining broodstock is released, but it will be dealing in triploid rainbows rather than the mix of browns and rainbows it currently produces.
The trout that were released in the river are a mix of about 70 percent browns and 30 percent rainbows.
“We’re not quite done releasing the broodstock. We have at least one more event planned,” Erdman said. “And we just thought it was good to let all the anglers know these big fish are out there.”
Times reporter Wendilyn Grasseschi contributed to this report.