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Experiments were carried out aboard vessels in the Danish North Sea hake gillnet fishery to determine if increasing the spacing of Aqutec AQUAmark100 pingers could be done without negatively impacting the effectiveness of the pinger. Control nets without pingers were tested alongside nets with pingers spaced at 455 m and 585 m. The control nets had a bycatch frequency of 0.54 incidents/haul for harbour porpoises. Nets with pingers spaced at 455 m had an incidence rate of 0 and nets with pingers spaced at 585 m had a bycatch frequency rate of 0.12. Bycatch indences were significantly different between the control and two experimental groups. This suggests that the spacing of pingers may be increased without significantly impacting their ability to reduce bycatch of harbour porpoises. 

Blue sharks account for most of the bycatch in the Canadian pelagic longline swordfish fishery. Electropositive metals (e.g. lanthanide) oxidize in seawater and create electric fields, which can alter the behaviors of several species of sharks. Researchers deployed seven sets (6300 hooks) with three hook treatments (standard hooks, hooks with electropositive metals - neodymium/praseodymium - and hooks with lead weights) on the Scotian Shelf in the Northwest Atlantic. Electropositive metals did not reduce the catch of blue sharks or other common shark bycatch species.  

This paper is a global assessment of marine mammal (cetacean, pinniped, sirenian, and marine mustelids) bycatch in gillnets and other entangling nets from 1990 to 2011. The authors found that at least 75% of odontocete species, 64% of mysticetes, 66% of pinnipeds, and all sirenian and marine mustelids have been recorded as gillnet bycatch over the past 20 years. 

This paper is a global review of seabird bycatch in gillnets. The authors identified 148 seabird species as susceptible to bycatch in gillnets, of which 81 have been recorded incidentally caught. A review of reported bycatch estimates suggests that at least 400,000 birds die in gillnets each year. The highest levels of bycatch are reported in the Northwest Pacific, Iceland, and the Baltic Sea.  

Studies were conducted aboard beam trawlers in the North Sea to determine the performance of pulse beam compared to conventional tickler chain beam trawlers.  Overall the pulse beam trawl caught 68% less than the conventional trawls.  Specifically, the pulse beam trawl caught significantly fewer plaice and sole compared to the conventional beam trawl. There was no significant difference in catch rates of undersized plaice between the two gears but the pulse beam trawl caught significantly less undersized sole.  Pulse beam trawls caught more turbot and brill (78%-131%) than conventional trawls but fewer cod (15%-60%).  In addition, catch rates of bottom species, including sandstar, common starfish and swimming crabs, were significantly less when the pulse beam trawl was used.

Fumunda acoustic alarms were tested in the absence of nets to determine their ability to modify the behavior of Australian snubfin and humpback dolphins, with possible applications to gillnet fisheries. The alarms emitted a regular interval pulse of 300 ms every 4 seconds at 10 kHz frequency.  The behavior of the animals changed slightly when the alarms were used but the likelihood of them leaving the area was not significantly different from the control.  This suggests this type of acoustic alarm may not be useful as a bycatch mitigation measure for these species.

Experimental trials were carried out in Argentina comparing franciscana bycatch rates in standard gillnets with gillnets with increased acoustic reglectivity by infusion with barium sulphate (BaSO4) and increased flexural stiffness of the nylon twine. There was no significant difference in franciscana bycatch rates or target catch rates among the three net types.  

Experimental trials were carried out in Argentina comparing franciscana bycatch rates in standard gillnets with gillnets with increased acoustic reglectivity by infusion with barium sulphate (BaSO4) and increased flexural stiffness of the nylon twine. There was no significant difference in franciscana bycatch rates or target catch rates among the three net types.  

Several seabird bycatch mitigation techniques were tested aboard distant water tuna fisheries in the South African EEZ.  Two types of bird scaring designs, light lines with short streams vs. hybrid lines with a mix of streamer lengths were compared with unweighted branch lines. In addition, unweighted to weighted branch lines were tested and night vs. day setting with a combination of bird scaring lines were tested for their effects on seabird avoidance and targeted fish catch rates.  A total of twenty seven seabird species were observed, but white-chinned petrels were the most common seabird observed and had the highest seabird mortality rate in the study. Albatross (black-browed, yellow-nosed and shy-type) also suffered high mortality rates while stealing bait from the petrels.  Other common surface foraging species included cape petrels. Hybrid lines did appear to reduce sea bird attacks for both species, but the results are not conclusive because the birds could still attack the line at points not protected by the bird scaring lines.  Sets made at night caught far fewer seabirds (0.439 birds/1000 hooks vs. 2 birds/1000 hooks) and catch rates were 18 times higher on the unweighted compared to weighted branch lines (1.07 birds/1000 hooks and 0.06 birds/1000 hooks respectively). The weighted and unweighted branch lines did not affect targeted fish catch rates.

Several seabird bycatch mitigation techniques were tested aboard distant water tuna fisheries in the South African EEZ.  Two types of bird scaring designs, light lines with short streams vs. hybrid lines with a mix of streamer lengths were compared with unweighted branch lines. In addition, unweighted to weighted branch lines were tested and night vs. day setting with a combination of bird scaring lines were tested for their effects on seabird avoidance and targeted fish catch rates.  A total of twenty seven seabird species were observed, but white-chinned petrels were the most common seabird observed and had the highest seabird mortality rate in the study. Albatross (black-browed, yellow-nosed and shy-type) also suffered high mortality rates while stealing bait from the petrels.  Other common surface foraging species included cape petrels. Hybrid lines did appear to reduce sea bird attacks for both species, but the results are not conclusive because the birds could still attack the line at points not protected by the bird scaring lines.  Sets made at night caught far fewer seabirds (0.439 birds/1000 hooks vs. 2 birds/1000 hooks) and catch rates were 18 times higher on the unweighted compared to weighted branch lines (1.07 birds/1000 hooks and 0.06 birds/1000 hooks respectively). The weighted and unweighted branch lines did not affect targeted fish catch rates.