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>> Cali plans to plant triploid trout in 2011 [topic: previous/next]
PostPosted: Tue May 11, 2010 4:54 pm

Posts: 2221
Location: Pacifica, CA

" California hatchery-raised rainbows may not be the happiest trout on earth. Next year, they are all going to be sterile.

The California Department of Fish & Game in 2011 will begin raising sterile trout, also known as “triploid” trout, for planting in lakes and streams that have access to water with anadromous trout.

Triploid trout are oftentimes raised to grotesque proportions and planted in lakes for derbies and promotions. The “world record” rainbow is a 43-pound, six-ounce triploid caught in June, 2007 from Lake Diefenbaker in Saskatchewan, Canada.

But California trout anglers should not get their hopes up, if their hopes include fishing for Frankentrout.

The only difference between the fertile trout currently being planted and the sterile trout soon to be produced will be just that – fertility.

The DFG plants catchable rainbows after they grow to a half-pound as part of a “put-and-catch” fishery that is designed for anglers to have at them for a short time. Survivability and growth are not a goal of the program. Sterile trout will be raised to the same half-pound before being released. There will not be an attempt to engineer monster trout.

“The main purpose of using triploid trout is so there is not a genetic impact from hatchery rainbow trout on wild rainbow trout, especially anadromous rainbow trout and steelhead,” said Curtis Milliron, a senior biologist with the DFG’s Inland Fishery pre-stock program. “There may be specific factors that would impact whether we see especially large trout from some we’ve planted but these will be roadside, catchable trout planted with the intention to be fished on right away.”

Milliron said all rainbow trout have the potential for large growth spurts if they find a healthy spot, but it is unknown whether a triploid will grow any larger than a fertile fish.

The put-and-take fishery differs from the put-and-grow program popular in Eastern Sierra lakes like Topaz and Crowley. In those cases, the lakes are planted in the late summer and early fall with trout weighing ¾ of a pound and by the spring they will have doubled and sometimes tripled in size.

California’s new program is similar to Idaho’s rainbow trout program. Since 2001 Idaho has stocked triploid trout to protect hybridization of its native cutthroat population. By all reports, the fish swim, fight, taste and appear to be “normal” trout.

Trout eggs are sterilized by exposing to a pressurizing process for a short time.

“It takes time to run the eggs through the system and there is a loss of efficiency,” Milliron said. “We could get a 30% survival rate and it might take some handpicking. There’s more work involved in producing sterile fish and because we will be new at it we don’t know what kind of success we’ll have.”

Millliron said the DFG will probably purchase sterile eggs from a private source to augment their own hatchery efforts so there will be enough trout to stock.

The move is in response to a lawsuit filed in 2006 by the Pacific Rivers Council and the Center for Biological Diversity against DFG claiming that DFG's fish stocking operation did not comply with the California Environmental Quality Act (CEQA). In July, 2007, DFG was ordered by the Sacramento Superior Court to comply with CEQA regarding its fish stocking operations. Among the areas of controversy were:

· Declines in certain amphibian species populations in higher‐elevation lakes and streams, in part due to predation by stocked trout.

· Alterations in the genetic makeup of native trout species due to interbreeding with stocked strains of rainbow trout;

· Changes in food webs and ecological systems in higher elevation areas where introduced trout compete for food with terrestrial wildlife.

· Declines in native salmon, steelhead, and trout populations, in part due to predation and competition for spawning grounds, food, and space from hatchery‐reared fish.

· alterations in the genetic makeup of native salmon and steelhead due to interbreeding with stocked strains of salmon and steelhead;

· Declines in native salmon, steelhead, and trout populations due to non‐target harvest associated with fishing for stocked fish."


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