Sperm whale and longline fisheries interactions in the Gulf of Alaska-passive acoustic component. North Pacific Research Board Project Final Report. F0412

Demersal longlining is a fishing technique where one to three miles of baited fishing line is placed on the ocean floor and left to “soak ” for 8-20 hours before being retrieved to haul black cod. Historical whaling records indicate that sperm whales (Physeter macrocephalus) off southeast Alaska incorporate fish into their diets, particularly black cod (Anoplopoma fimbria). In the 1970s sperm whales were encountered off longline gear in the Gulf of Alaska, but beginning in 1995 the frequency and intensity of depredation encounters between longline fishermen and sperm whales increased. Since 2002 the SE Alaska Sperm Whale Avoidance Project (SEASWAP) has been studying this phenomenon using fishermen reports, photo-ID, and biopsies (see related report by NPRB R0309). In 2004 and early 2005 both passive acoustic towed arrays and autonomous recorders mounted on longline deployments have provided an opportunity to both monitor and track sperm whale acoustic activity, whenever fishing vessels were present and absent. This report summarizes work on the passive acoustic component of the project (NPRB F0412) during 2004, with an emphasis on the development of passive acoustic technique