Acoustic pingers eliminate beaked whale bycatch in a gill net fishery
Bycatch of beaked whales in gill net fisheries has been documented worldwide (Nicholson 1954, Di Natale 1994, Read 1994, Siliciliano 1994, Julian and Beeson 1998, Waring et al. 2006). Acoustic pingers have been successfully used to reduce bycatch of harbor porpoises (Phocoena phocoena) (Kraus et al. 1997, Trippel et al. 1999, Gearin et al. 2000) and common dolphins (Delphinus delphis) (Barlow and Cameron 2003), but pinger efficacy in reducing beaked whale bycatch has never been evaluated due to the rarity of beaked whale entanglements in fisheries.We report that bycatch of beaked whales in a California drift gill net fishery dropped to zero when acoustic pingers were added to reduce cetacean bycatch and that this effect is much greater than bycatch reductions for other cetacean taxa. Our study is based on 17 yr of fishery observer data collected by biologists at sea aboard drift gill net vessels fishing for swordfish and sharks in the California Current (Julian and Beeson 1998, Carretta et al. 2005).