State biologists advise sampling, local removals to tackle Duck Lake’s grass carp problem

Washington Department of Fish and Wildlife staff told the Ocean Shores Freshwater Advisory Board that long‑standing plant‑grazing grass carp and an illegal introduction of yellow perch have combined to collapse Duck Lake’s fishery and drive summer algal blooms. Ken Behan, WDFW warm‑water program manager, said the next concrete steps are sampling fish to determine whether stocked grass carp are sterile and enabling community removal efforts.

Behan traced the problem to two grass carp stockings—one in 1994–95 and a second later—combined with herbicide treatments that reduced vegetation to “less than 5%” of target cover. That loss of nursery habitat, he said, enabled yellow perch to “explode,” shifting the lake’s biomass and leaving predominately small, low‑value perch. "We caught 4 yellow perch one year, then the next year we caught 80, and then it was thousands," Behan said, describing how overcrowding has driven early maturation and…