• Chambers, John S.
  Fisheries Biologist
  

The insecticide Sevin kills ghost shrimp, burrowing crustaceans, that reduce oyster production by smothering young oysters with castings from their burrows. Ten pounds per acre of the active chemical applied to exposed tideland is the most efficient concentration for controlling these pests. Either form of the chemical, granular or spray, is effective depending upon soil composition and topography of the infested area.

Sevin is only slightly soluble in water, and it quickly dissipates from the soil and marine animal tissues. It is relatively nontoxic so mammals but is lethal to crustaceans, worms, and some small fishes trapped and unable to escape high concentrations. Some animals appear irritated but survive. Although some clams have been killed, no mortalities  of oysters have been observed, and none to negligible amounts of Sevin have been assayed in oyster meats in as short a time as 1 day after treatment.

Sevin is U.S.F.D.A. approved for application to certain land farm crops, but tolerance levels have not been established for marine products. At the present time, Sevin is used on oyster land under an experimental-use permit rigidly controlling the application, and the effects are studied by Fisheries Department personnel. Authorization for issuance of the permits is made annually by the Washington Department of Agriculture to the Department of Fisheries.