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Summary:

Acoustic Harassment Devices (AHDs) were shown to exclude harbor porpoise (Phocoena phocoena) from bays in British Columbia.

Summary: 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.).

Summary: Harbor porpoise (Phocoena phocoena) avoided an area around a non-lethal, experimental gillnet equipped with a pinger in British Columbia, Canada. In a separate experiment with gillnets in the Baltic Sea, pingers did not affect the catch of targeted herring (Clupea harengus).

Summary:

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.  

Summary:

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.  

Summary:

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.

Summary: Gillnets equipped with acoustic pingers caught only one harbor porpoise (Phocoena phocoena) compared to 42 caught in control nets off of New Hampshire, USA. Alarms sounds are above groundfish hearing and are not expected to affect fish catch.

Summary: Metal oxide nets containing barium sulphate (that increased their acoustic reflectivity and probably also their stiffness) reduced the bycatch of harbor porpoise (Phocoena phocoena) in an eastern Canada demersal gillnet fishery. No difference in catch of commercial fish species, including cod, pollock, haddock, and spiny dogfish, was observed between the nylon and barium sulphate nets. Metal oxide nets reduced the bycatch of greater shearwater (Puffinus gravis) in an eastern Canada demersal gillnet fishery, probably by increasing the visibility of the blue-dyed nets to the birds.

Summary: Metal oxide nets made from barium sulphate increased the detectability of gillnets by marine mammals when compared to nylon nets when approached at angles of incidence greater than normal incidence but less than 40 degrees. Hypothesized detection ranges indicate bottlenose dolphins (Tursiops truncatus) should be able to detect metal oxide nets in time to avoid entanglement, but harbor porpoise (Phocoena phocoena) may not be able to detect either net in time to avoid contact.

Summary:

Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass pair trawl fishery did not reduce bycatch of common dolphins (Delphinus delphis). Multi-monofilament net, placed in the North Sea and West of Scotland gillnet fisheries, had no significant impact on harbour porpoise (Phocoena phocoena) bycatch when compared to traditional monofilament net. Thin twine monofilament nets (.4mm twine diameter, 90 mm mesh size) reduced bycatch of harbour porpoise (Phocoena phocoena) and seals in the North Sea and West of Scotland gillnet fisheries when compared to thick (.6mm twine diameter, 267 mm mesh size) monofilament nets. Barium sulphate nets had higher bycatch of harbour porpoise (Phocoena phocoena) and seals in the North Sea and West of Scotland gillnet fisheries when compared to traditional gillnets.