This past week we restocked two of our LMD lakes in Washington State with Triploid Grass Carp. These sterile fish are helping us keep problem aquatic plant growth suppressed in this lake system. In 2002, we build and installed fish passage screens that allow salmon and cutthroat trout to move back and forth to the saltwater below these lakes while holding the grass carp in. Over the past seven years, these fish have played a key role in keeping excessive vegetation in check while we have used other technologies to spot treat invasive aquatic weeds when necessary. This stocking was to augment the biological control agent populations in the lakes and replace fish lost to mortality and predation.
Managing using biological control agents required constant monitoring of the pressure on the target plant and managing the population of the biocontrol agent to insure control is achieve without over controlling vegetation in the lake. Our biologists monitor these conditions and adjust stocking rates as necessary using a permit from the Washington Department of Fish and Wildlife.