In a news statement from the folks at the North Carolina Wildlife Commission in Raleigh fisheries supervisor Mallory Martin has some interesting plans to share. Hatchery- raised trout stocked in NC 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 NCWRC gradually has been shifting its production of trout from those that can produce fry 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, NC.
Hatcheries raise northern brook trout, which have mixed with native brookies, reducing the native trout population. Genetic assessments show 39% of NC brook troutare pure natives, 9% are direct descendents of northern brookies and 52% are a mixture. Sterile trout can reduce this 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 NC might be the 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. NC WILDLIFE RESOURCES COMMISSION @ 2008