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Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass (Dicentrarchus labrax) 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.

Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass (Dicentrarchus labrax) 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.

Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass (Dicentrarchus labrax) 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.

Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass (Dicentrarchus labrax) 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.

Acoustic pingers placed in the rear of a pair trawl net in the United Kingdom bass (Dicentrarchus labrax) 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.

Pingers were tested to reduce harbor porpoise (Phocoena phocoena) bycatch in bottom-set gillnets in the Swedish Skagerrak Sea. During the experiment, no harbor porpoise were caught in control or experimental gillnets, possibly as a result of a combination of factors including displacement of porpoise, high prey availability in other areas, or pingers acting as passive reflectors. Pingers did not affect the catch of target species, including cod (Gadus morhua) and pollock (Pollachius pollachius).

Harbour porpoise (Phocoena phocoena) bycatch was significantly lower (p<0.01) in high-density Iron Oxide (IO) gill nets compared to control nets. There was no significant difference in the acoustic target strength of the IO and control nets, and both nets behaved similarly in flume tank tests. The authors conclude the reduction of harbour porpoise bycatch in the IO nets was a result of the mechanical properties of the nets.

Gillnets fitted with Dukane NetMark 1000 pingers had significantly less bycatch of harbor porpoises (Phocoena phocoena) than control nets and the fish size and catch rates of the target species were not affected.

Gillnets from the North Sea wreck net fishery equipped with pingers had a 100% reduction in the bycatch of harbour porpoises (Phocoena phocoena) compared to nets with no pingers attached.

Bottom set gillnets with pingers (LU-1, 8 signals, 145 dB, 300 ms, random signal intervals) attached were tested against standard nets and nets with dummy pingers (double blind) to determine if they could reduce the incidental capture of harbor porpoises (Phocoena phocoena). The proportion (number of nets with porpoises/number without) of harbour porpoise bycatch was reduced from 0.00229 and 0.00295 for nets with dummy pingers and no pingers respectively, to 0.00015 for nets with active pingers. The difference in bycatch rates between nets with active and dummy pingers was statistically significant but not between nets with dummy pingers and with no pingers.