Shipworm (Bankia setacea) activity within the Port of Everett and the Snohomish River Estuary: Defining the problem

Abstract

Log rafts stored in the Snohomish River estuary, a facility maintained by the Port of Everett, Washington, were infested by shipworms (Bankia setacea) during 1987. Studies were done to identify when the log rafts were infested, establish relationships between estuarine conditions and shipworm attack, and examine the potential for future infestations. The first two objectives were studied by retracing in time and place the patterns of log raft movements and by developing a salt water intrusion model. The last objective was met by developing a river flow predictive model. The timing of log raft movements and storage during periods of low river flow and high B. setacea larval settlement were responsible for the shipworm infestations. In particular, uncommonly low river flow in 1987 created estuarine salt water conditions favorable for shipworm activity in the normally safe log storage areas. If the late summer trend in freshwater flow reduction observed since 1963 continues, then by the year 2000, the average monthly flow during the period of maximum shipworm settlement will drop by about a third from current flow levels. Under these conditions, saltwater intrusion and B. setacea damage will become more common within the estuary. Key words: shipworms, log rafts, log storage, estuarine conditions, saltwater intrusion, river flow, predictive models