Unanswered Forum Topics

Pelagic gillnet modification trials in northern Australian seas

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Passive acoustic deterrents in the form of chains of metallic beads and air-filled plastic tubing attached to gillnets in Australia did not reduce bycatch of two small cetaceans: the Atlantic bottlenose dolphin (Tursiops truncatus) and Spinner dolphin (Stenella longiristris). A sub-surface set gillnet (set 4.5 m below the surface) in Australia reduced cetacean catch rate [Atlantic bottlenose dolphin (Tursiops truncatus) and Spinner dolphin (Stenella longiristris)] when compared to a standard surface set net.

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Field Experiments Show That Acoustic Pingers Reduce Marine Mammal Bycatch in the California Drift Gill Net Fishery

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Pingers reduce bycatch of California sea lions (Zalophus californianus) and short-beaked common dolphins (Delphinus delphis) in the California drift gillnet fishery for swordfish and sharks. Catch of target fish species (broadbill swordfish, common thresher shark, and shortfin mako shark) and non-target species were not affected by pinger use.
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Experimental testing of acoustic alarms (pingers) to reduce bycatch of harbor porpoise, Phocoena phocoena, in the state of Washington

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Pingers do not reduce bycatch of harbor seals (Phoca vitulina) in the salmon and sturgeon gillnet fisheries in northern Washington state but do reduce bycatch of harbor porpoise (Phocoena phocoena). Pingers did not affect catch of target species, chinook salmon (Oncorhynchus tshawytscha) and sturgeon (Acipenser sp.).
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Reducing bycatch: can acoustic pingers keep Hector's dolphins out of fishing nets?

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Acoustic pingers were tested for their effectiveness to reduce entanglement of Hector's dolphins in New Zealand gillnets. A remote control device was used to raise either active or passive acoustic pingers near Hector's dolphins. The dolphins' movement and distribution was observed from shore.Dolphins avoided the immediate area when pingers were active, but did not leave the larger harbor area. Dolphin sightings made during active pinger trials were distributed significantly farther from the source than during passive trials. 

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Deterring harbour porpoise from gillnets: observed reactions to passive reflectors and pingers

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Three different device types were mounted on floatline to test their potential for reducing harbor porpoise bycatch. The devices were two passive reflectors (target strength ranging from -38 dB to -24 dB) and a 2.9 kHz pinger. Behavioral responses of 355 harbor porpoise groups were monitored. 92.4% of the groups avoided the pinger equipped floatline, while only half the groups avoided the reflectors and control, empty, floatline.  

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Fishing methods to reduce sea turtle mortality associated with pelagic longlines

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18/0 circle hooks when compared with J hooks significantly reduce loggerhead (Caretta caretta) and leatherback (Dermocheles coriacea) sea turtle bycatch in Atlantic longline fisheries for pelagic swordfish. Circle hooks also reduced the rate of hook ingestion by loggerhead sea turtles. The combination of circle hooks and mackerel bait was the most effective in reducing sea turtle bycatch and had no negative effect on swordfish catch.

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Acoustic alarms reduce porpoise mortality

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Acoustic alarms reduce bycatch of harbor porpoises (Phocoena phocoena) in the Gulf of Maine sink gillnet fishery. Gillnets with and without acoustic alarms caught similar quantities of target species, cod and pollock. Acoustic alarms did not affect catch of bycaught silver hake, but Atlantic herring was caught less frequently in experimental nets with alarms. Harbour seals depredated fish caught in both nets with and without acoustic alarms.

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