Study

Seal mitigation measures on trawl vessels fishing for krill in CCAMLR subarea 48.3

  • Published source details Hooper J., Clark J.M., Charman C. & Agnew D. (2005) Seal mitigation measures on trawl vessels fishing for krill in CCAMLR subarea 48.3. CCAMLR Science, 12, 195-205.

Actions

This study is summarised as evidence for the following.

Action Category

Install exclusion and/or escape devices for mammals on fishing nets

Action Link
Marine and Freshwater Mammal Conservation

Install exclusion and/or escape devices for mammals on fishing nets

Action Link
Marine and Freshwater Mammal Conservation

Install exclusion and/or escape devices for mammals on fishing nets

Action Link
Marine and Freshwater Mammal Conservation
  1. Install exclusion and/or escape devices for mammals on fishing nets

    A controlled study in 2004 of a pelagic site in the South Atlantic Ocean, South Georgia (Hooper et al. 2005) reported that installing exclusion and escape devices on trawl nets resulted in fewer Antarctic fur seal Arctocephalus gazella entanglements compared to when no devices were installed. Results are not based on assessments of statistical significance. Fewer seals were entangled when exclusion and escape devices were installed within trawl nets (total 28 seals; 0.2 seals/trawl) than when no devices were installed (total 157 seals, 1.9 seals/trawl). A commercial fishing vessel (‘Top Ocean’, USA) trawling for krill (Euphausiacea) with two nets carried out 118 trawls with exclusion and escape devices on both nets, and 81 trawls without devices installed. Exclusion and escape devices on each net were modified throughout the study (see original paper for details). The final design had an inclined mesh barrier (140 mm mesh size) within the net, 1–3 escape openings (1–1.6 m diameter) in the roof of the net, and a large mesh barrier (14 x 12 m) inserted 47 m from the mouth of the net. Seal entanglements were recorded by fishers (30 trawls) and an independent observer (169 trawls) in June–July 2004.

    (Summarised by: Anna Berthinussen)

  2. Install exclusion and/or escape devices for mammals on fishing nets

    A study in 2004 of a pelagic site in the South Atlantic Ocean, South Georgia (Hooper et al. 2005) reported that installing two designs of exclusion device on trawl nets resulted in fewer Antarctic fur seal Arctocephalus gazella entanglements compared to when no device was installed. Results are not based on assessments of statistical significance. Fewer seals were entangled in trawl nets with a mesh barrier (total 5 seals, 0.8 seals/trawl) or a mesh ‘bag’ (total 2 seals, 0.06 seals/trawl) installed at the mouth of the net compared to when no exclusion device was installed (total 76 seals, 1.4 seals/trawl). The mesh barrier also reduced target fish catches (data not reported). A commercial fishing vessel (‘InSung Ho’, Republic of Korea) trawling for krill (Euphausiacea) carried out six trawls with a mesh barrier, 42 trawls with a mesh ’bag’ and 55 trawls without an exclusion device installed. The mesh barrier comprised two mesh panels (44 x 20 m; 240 mm mesh size) attached to the head rope and ground rope at the mouth of the trawl net. The mesh ‘bag’ comprised one mesh panel (240 mm mesh size) attached to the mouth of the trawl net and extending 20 m into the body of the net to form a large ‘bag’. Seal entanglements were recorded by fishers (eight trawls) and an independent observer (95 trawls) in August 2004.

    (Summarised by: Anna Berthinussen)

  3. Install exclusion and/or escape devices for mammals on fishing nets

    A study in 2004 of a pelagic site in the South Atlantic Ocean, South Georgia (Hooper et al. 2005) reported that modifying an exclusion and escape device by enlarging and relocating the escape panel resulted in fewer Antarctic fur seal Arctocephalus gazella entanglements. Results are not based on assessments of statistical significance. A total of 11 seals (6 seals/trawl) were entangled in trawl nets with an exclusion device angled towards a small escape panel in the roof of the net. However, after the exclusion device was angled towards a larger escape panel in the floor of the net, no seals were found entangled. A commercial fishing vessel (‘Atlantic Navigator’, Vanuatu) carried out a total of 15 trawls for krill (Euphausiacea) with a sloping metal grid angled towards an escape panel within the trawl net. In the first two trawls, a smaller escape panel (size not reported) was located within the roof of the net. In the following 13 trawls, the escape panel was larger (size not reported) and located in the floor of the net. During trawls, the net was kept at fishing depths for long periods and a pump used to remove krill. Seal entanglements were recorded by fishers (two trawls) and an independent observer (13 trawls) in June–July 2004.

    (Summarised by: Anna Berthinussen)

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