Study

Size selection of three commercial fish using sorting grids in the Persian Gulf shrimp trawl fishery

  • Published source details Paighambari S.Y. & Eighani M. (2016) Size selection of three commercial fish using sorting grids in the Persian Gulf shrimp trawl fishery. Regional Studies in Marine Science, 3, 251-253.

Actions

This study is summarised as evidence for the following.

Action Category

Fit a size-sorting escape grid (rigid or flexible) and large, supported escape openings to trawl nets

Action Link
Marine Fish Conservation

Fit a size-sorting escape grid (rigid or flexible) to a prawn/shrimp trawl net

Action Link
Marine Fish Conservation
  1. Fit a size-sorting escape grid (rigid or flexible) and large, supported escape openings to trawl nets

    A replicated, paired, controlled study in 2013 of shallow, coastal waters in the Persian Gulf off Iran (Paighambari & Eighani 2016) found that shrimp trawl nets fitted with one of two experimental rigid sorting grids (Nafted or Nordmøre) and either with or without a large, supported escape opening (Fisheye) caught fewer small, unwanted fish compared to a standard trawl without a grid or opening. The Nafted/Fisheye trawl net caught 53% fewer narrow-barred Spanish mackerel Scomberomorous commerson, 45% fewer tigertooth croaker Otolithes ruber and 55% fewer silver pomfret Pampus argenteus than the standard trawl. The trawl with the Nordmøre grid alone caught 59% fewer mackerel, 45% fewer croaker and 55% fewer pomfret than the standard trawl. In total, 15 trawl deployments with each grid type were conducted from a commercial fishing vessel in 2013 in depths of 13–33 m. Tows were 1.5 h long at speeds of 2.5–3 knots. Trawls were double rigged and towed an experimental net alongside a standard net. Both grid types were inclined at 45° with 60 mm bar spacing. The Nafted grid had a Fisheye steel frame sewn into the top of the codend for fish to escape (see paper for gear specifications).

    (Summarised by: Chris Barrett)

  2. Fit a size-sorting escape grid (rigid or flexible) to a prawn/shrimp trawl net

    A replicated, paired, controlled study in 2013 of shallow, coastal waters in the Persian Gulf, Iran (Paighambari & Eighani 2016) found that shrimp trawl nets fitted with a rigid size-sorting escape grid (a Nordmore grid) caught fewer undersized fish compared to a trawl net without a grid. The net with a grid caught lower proportions of undersized individuals of three of three fish species: narrow-barred Spanish mackerel Scomberomorous commerson (with: 11%, without: 36%), tigertooth croaker Otolithes ruber (with: 29%, without: 43%) and silver pomfret Pampus argenteus (with: 13%, without: 15%). For each species, the length at which half were likely to escape was smaller than the minimum landing sizes. In addition, compared to a 32% reduction in average exclusion rate of undersized fish with a Nordmore grid, a trawl net fitted with a different design of grid (Nafted) and an additional large supported escape opening (Fisheye), reduced the undersized catches by 47%. Data were collected from a total of 30 valid trawl deployments (15 tows for each grid design) conducted by a commercial vessel in 2013. Test trawl nets fitted with grids were towed for 1.5 h alongside nets without grids in depths of 13–33 m. Codends were all of 30 mm mesh size. Both the Nordmore and Nafted grids had 60 mm bar spacing at were fitted at a 45° angle. The Nafted grid was fitted in combination with a Fisheye escape opening, a steel frame sewn into the top of the codend to provide an elliptical opening of 400 mm for fish escape.

    (Summarised by: Chris Barrett)

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