N.C. will stock sterile trout

Change planned to protect native fish

Hatchery-raised trout stocked in North Carolina's streams beginning in 2009 won't experience parenthood.

That's because all brook, brown and rainbow trout will be sterile and unable to reproduce.

The N.C. Wildlife Resources Commission gradually has been shifting its production of trout from those that can produce fry in the wild to those that won't be able to spawn offspring.

The impetus for converting to sterile trout is to help preserve the native Southern Appalachian brook trout, said Mallory Martin, the commission's regional fisheries supervisor in Marion.

Hatcheries raise northern brook trout, which have mixed with native brookies, reducing the native trout population.

Genetic assessments show 39 percent of N.C. brook trout are pure natives, 9 percent are direct descendants of northern brookies and 52 percent are a mixture. Sterile trout can reduce hybridization.

"The primary reason is to preserve the genetic integrity of our Southern Appalachian brook trout," said Doug Besler, cold-water research coordinator.

When fishery technicians begin the 2009 stockings, all 800,000 fish will be sterile or, as they're known to biologists, triploids. About half the fish stocked in 2008 will be triploids. Triploids look and act like non-sterile fish but grow faster.

Each year, fishery technicians release hatchery fish into 1,100 miles of hatchery-supported waters and into 18 delayed-harvest stream segments and lakes managed for catch-and-release. Martin said only a few reproduce in the wild.

Another benefit to stocking sterile trout is that any less-hardy hatchery fish that make their way upstream into wild-trout sections can't breed with naturalized rainbows and browns and, consequently, weaken their gene pools.

He said the agency until 1970 supplemented wild-trout streams with stocked fish. No longer.

"We don't go back to wild trout waters with hatchery fish," he said.

Martin said North Carolina might be the first Southeastern state to go with sterile trout. Virginia has been experimenting with triploids. Idaho stocks triploid rainbows to protect native cutthroat trout.

To create triploids, hatchery workers pressure-treat trout eggs inside a metal chamber. The pressure results in an extra set of chromosomes, three rather than two, thus making the unborn fish sterile.

FISH KILL WON'T REDUCE STOCKINGS: Despite a large fish kill at Armstrong State Fish Hatchery last month, the N.C. Wildlife Resources Commission says it should be able to fulfill its trout stocking plan this season.

Heat and drought caused the deaths of more than 103,000 brown and rainbow trout at the cold-water fish hatchery located in McDowell County, the commission said in a Sept. 5 news release. Most of the fish were scheduled for stocking next year.

The agency said its other two trout hatcheries have produced enough trout for this fall's delayed-harvest season and for the 2008 stocking season.