Base Lake stocked with 10,000 redear sunfish

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  • By 55th Wing Public Affairs
OFFUTT AIR FORCE BASE, Neb. --  The U.S. Fish and Wildlife Service transferred 10,000 redear sunfish from the Valentine State Fish Hatchery to the Base Lake on Offutt Air Force Base, Neb., Oct. 19.

The hope is the fish will serve as a potential management tool for zebra mussels, who were accidently introduced to the lake back in 2006.

"Stocking redear sunfish was a recommendation from both the U.S. Fish and Wildlife Service and the Nebraska Invasive Species Advisory Council," said Dan James, U.S. Fish and Wildlife Service fish and wildlife biologist, who transferred the fish. "Redear sunfish have a specialized structure in their mouth called a molariform pharyngeal tooth, which enables them to crush zebra mussel shells in order to eat the mussel inside the shell."

Zebra mussels are native to fresh water lakes in southern Russia and have been spreading to waterways in the United States since the 1980s. After their discovery in the Base Lake, the base teamed with state and federal offices to treat the water with copper sulfate in 2008 and 2009 in hopes of eradicating the population.

Unfortunately, U.S. Fish and Wildlife Service biologists confirmed the re-establishment of zebra mussels at the lake in 2014, and since then the population has continued to increase.

Redear sunfish are known as consumers of the mussels but it is unknown how well zebra mussel mitigation might work using redear sunfish.

"A few scientific studies have shown that redear sunfish do eat zebra mussels, so we thought they might do the same in Offutt Base Lake," James said.

"In one of these studies 100 percent of the redears were found to have consumed zebra mussels as their primary prey," said Marvin Riedel, 55th Civil Engineer Squadron environmental compliance officer.

The idea of adding redear sunfish to the base lake was proposed by U.S. Fish and Wildlife, Nebraska Game and Parks and the Nebraska Invasive Species Project a few years ago. Thanks to a collaborative effort between the Gavins Point National Fish Hatchery, Nebraska's Valentine State Fish Hatchery and the U.S. Fish and Wildlife Service Great Plains Fish and Wildlife Conservation Office, this effort finally came to fruition.

"We have all been communicating since last year in the hopes of raising redear sunfish to stock into Offutt Base Lake," James said. "Doug Graham and his crew from the Valentine hatchery have experience raising the fish, so they raised some broodstock fish for Gavins Point to start their own program and were also able to raise an extra 10,000 fish beyond their own needs. We thank the Valentine hatchery very much for providing these fish."

The U.S. Fish and Wildlife Service and 55th CES will evaluate their survival and effectiveness as predators in the future.

"We hope the redears will adapt to conditions in the lake quickly and start eating zebra mussels next summer," James said. "We will monitor their survival, growth rates, and even analyze their diets by pumping out their stomachs to see how many mussels they are eating.  We are also monitoring the zebra mussel population numbers and will see if those numbers decrease over time."

"Our hopes are that the redear sunfish ... establish a breeding population which will incorporate zebra mussels into their regular diet to the extent that they will act as a control on the population of zebra mussels," Riedel said. "Currently there are no effective controls on zebra mussel breeding and population growth. Introducing a known zebra mussel predator could act as a significant brake on their growth rates."