No stocks this year, but triploid trout may be coming to county in 2011

By Guy Carl | Posted: Friday, April 30, 2010 12:00 am

Details are unfolding on how the new trout stocking protocols of the Department of Fish & Game will impact fishing waters in California.

The two public reservoirs in Napa County open to fishing, Lake Berryessa and Lake Hennessey, have been designated to potentially receive stockings of “triploid” rainbow trout.

However, the DFG will not have access to these fish until 2011. 

This means no new trout plantings will occur in these lakes this year.

Triploid trout are normal rainbows that have been genetically modified to be sterile, but are otherwise identical to other rainbow trout. They look, fight, and taste just the same.

But there is one exception to the similarities. With no ability to reproduce, triploids focus all of their energy on eating and growing large — sometimes to cartoonish proportions.

The most famous triploid trout come from Canada’s Lake Diefenbaker, where last year a triploid was landed that tipped the scales at a record 48 pounds! 

Granted, this fish was one of a huge batch that had escaped from a commercial trout farm nine years prior, but it is an example of how big these fish can get.

The science behind creating these monster fish happens during the incubation of the trout eggs.

A fertilized trout egg initially contains three sets of chromosomes — two from the female and one from the male. In nature, one of the chromosome sets is normally pushed out of the egg shortly after fertilization. If the extra set fails to be pushed out, the fish becomes a sterile “triploid.” At the hatcheries, these eggs can be induced to retain the third set by several methods.

The DFG will use a method of applying high pressure levels to the eggs immediately after fertilization, as well as purchasing already-modified triploid trout eggs from approved vendors.

According to DFG biologist Eric Larson, Lake Berryessa and Lake Hennessey are subject to trout stocking restrictions because they drain directly into steelhead spawning streams.

Through the mandated environmental impact studies done on the trout stocking program, it was found that the steelhead, a federally threatened species, could interbreed with the non-native strains of hatchery trout that could escape over the dam. So in order to protect the genetic integrity of the native steelhead, only the sterile triploids are allowed to be stocked in these lakes.

The final approval for stocking Berryessa and Hennessey is subject to the completion of the lake-specific environmental studies on these waters, expected to be finished later this year.

Larson is confident these studies will support the stocking of triploid trout.

Although there will be no trout stocks here in 2010, the DFG will be stocking Lake Berryessa with put-and-grow Chinook salmon. These fish will quickly to grow to legal catchable size. There is also a good hold-over population of trout from last year’s plants.

I’m looking forward to tying into some of these hawgs in our local lakes next year!


Kids’ Fishing Derby at Lake Hennessey May 23

Mark your calendar for the 41st annual George Carl Kids’ Fishing Derby, coming up on Sunday, May 23 at Lake Hennessey.

Put on by the Active 20-30 Club of Napa, the derby is open to all children between the ages of 3 and 16. There is no cost to enter the derby, and all participants receive a starter kit of fishing tackle along with a certificate of participation.

The date was set later than usual this year in hopes of catching a good late-spring bite of bass, bluegill and crappie.

More details will be published as the event date nears.

Guy Carl is a CPA and partner with BDCo Accountants and Advisors in St. Helena (www.bdcocpa.com).

Contact Guy at GC.outdoors@sbcglobal.net.