By Deb Murphy
After six years of stocking non-breeding (triploids) trout and following inter-departmental discussions, the California Department of Fish and Game will begin raising and stocking little breeders (diploids) in the Owens River and Mono Lake basins next spring.
CDF&W started stocking only sterile trout, statewide, in 2011 in response to lawsuits and an environmental study that indicated an impact to native fish and other native species, according to CDF&W’s environmental scientist Jim Erdman. The state’s native cutthroat and golden trout species could be compromised by cross-breeding with stocked rainbows.
But, there are no native cut throats or goldens in the Mono Lake or Owens River basins and no danger of cross-breeding, so the diploids are on their way back. Erdman stressed triploids will continue to be stocked in the Walker Basin.
Triploids are not technically genetically modified. Diploids have two sets of chromosomes; triploids are created by forcing the egg to retain a third complimentary chromosome normally ejected during egg development.
And, according to a study done by the Game and Wildlife Conservation Trust between March 2006 and May 2006, there isn’t much difference between the two. The diploids ranked a tick higher in fighting ability and visual condition. Both are equally likely to take dry flies, stated the study.
The switch from non-breeders to breeders won’t lead to a sustainable fishery in either basin, Erdman said. “There’s too much fishing pressure,” he said.
Despite the study results, the re-introduction of breeders should be applauded by the fishing community who never really believed the sterile triploids were up to par with their breeding brethren.