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Providing evidence to improve practice

Individual study: The impact of turtle excluder devices and bycatch reduction devices on diverse tropical marine communities in Australia's northern prawn trawl fishery.

Published source details

Brewer D., Heales D., Milton D., Dell Q., Fry G., Venables B. & Jones P. (2006) The impact of turtle excluder devices and bycatch reduction devices on diverse tropical marine communities in Australia's northern prawn trawl fishery. Fisheries Research, 81, 176-188


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Fit one or more mesh escape panels/windows and one or more soft, rigid or semi-rigid grids or frames to trawl nets Subtidal Benthic Invertebrate Conservation

A replicated, paired, controlled study in 2001 in areas of seabed in the Gulf of Carpentaria, northern Australia (Brewer et al. 2006) found that nets fitted with a mesh escape window (“bycatch reduction device”) and a grid (“turtle excluder device”), caught fewer large sponges and reduced the total weight of small unwanted catch (invertebrates and fish combined), compared to unmodified nets. Nets fitted with both escape window and grid caught 85% fewer large sponges and reduced the weight of small unwanted catch by 8%, compared to unmodified nets. The modified nets reduced the catch of commercially targeted prawns by 6%. The use of a “turtle excluder device” and a “bycatch reduction device” has been compulsory since 2000 in the Australian prawn fishery. Commercial vessels towed twin Florida Flyer prawn trawl nets from each side of the vessels in August–November 2001. Modified nets were fitted with both one of two designs of escape window (a “Bigeye” design or a square-mesh escape window) and one of 23 grid designs (rigid or semi-rigid frame with ≤120 mm bar spacing and an opening of ≥700 mm). A modified and an unmodified net were randomly assigned to either side of the vessel and towed simultaneously (324 modified nets examined for small unwanted catch, 150 for sponges; 703 unmodified nets for small unwanted catch, 339 for sponges). Total weights of small unwanted catch (<300 mm), commercially targeted prawns, and counts of sponges (>300 mm) were recorded. The combinations of various device designs were not compared. The “Bigeye” design was later removed from the Australian list of approved escape zone designs.

(Summarised by Anaëlle Lemasson & Laura Pettit)

Fit one or more soft, semi-rigid, or rigid grids or frames to trawl nets Subtidal Benthic Invertebrate Conservation

A replicated, paired, controlled study in 2001 in areas of seabed in the Gulf of Carpentaria, northern Australia (Brewer et al. 2006) found that the effects of fitting a grid (“turtle excluder device”) to trawl nets, on large sponges and small unwanted catch (invertebrates and fish combined) varied with the device orientation. Nets fitted with a device oriented either ‘downward’ or ‘upward’ caught 82–96% fewer large sponges, compared to unmodified nets, but only the ‘downward’ devices reduced the weight of small unwanted catch (by 8%; data not provided for the ‘upward’ device). Compared to unmodified nets, nets fitted with a ‘downward’ device reduced the catch of commercially targeted prawns by 6%, while those with an ‘upward’ device caught similar amounts. The use of a “turtle excluder device” has been compulsory since 2000 in the Australian prawn fishery (as well as the use of a “bycatch reduction device”). Commercial vessels towed twin Florida Flyer prawn trawl nets from each side of the vessel in August–November 2001. Nets with one of 23 grid designs (rigid or semi-rigid frame with ≤120 mm bar spacing and an opening of ≥700 mm) grouped as either ‘upward’ (9 devices) or ‘downward’ (14 devices) oriented (267 nets examined for small unwanted catch, 392 for sponges) and an unmodified net (339 for sponges, 703 for small unwanted catch) were randomly assigned to either side of the vessel. Total weights of small unwanted catch (<300 mm), commercially targeted prawns, and counts of sponges (>300 mm) were recorded.

(Summarised by Anaëlle Lemasson & Laura Pettit)

Fit one or more mesh escape panels/windows to trawl nets Subtidal Benthic Invertebrate Conservation

A replicated, paired, controlled study in 2001 in seabed areas in the Gulf of Carpentaria, northern Australia (Brewer et al. 2006) found that nets fitted with either one of two escape zone designs (“bycatch reduction device”) did not reduce the numbers of large sponges caught or weight of small unwanted catch (invertebrates and fish combined), compared to unmodified nets. Data were not provided. Nets fitted with a ‘Bigeye’ escape zone reduced the catch of commercially targeted prawns by 4.2% compared to an unmodified net, while nets fitted with a square-mesh escape panel caught similar amounts. The use of a “bycatch reduction device” has been compulsory since 2000 in the Australian prawn fishery (as well as the use of a “turtle excluder device”). Commercial vessels towed twin Florida Flyer prawn trawl nets from each side of the vessel in August–November 2001. Nets fitted with one of the two designs of escape zone (112 nets examined for small bycatch, 97 for sponges) and an unmodified net (703 for small bycatch, 339 for sponges) were randomly assigned to either side of the vessel. Total weights of small unwanted catch (<300 mm), commercially targeted prawns, and counts of sponges (>300 mm) were recorded. The “Bigeye” design was later removed from the Australian list of approved designs.

(Summarised by Anaëlle Lemasson & Laura Pettit)