Study

Development and observations of a spiny dogfish Squalus acanthias reduction device in a raised footrope silver hake Merluccius bilinearis trawl

  • Published source details Chosid D.M., Pol M., Szymanski M., Mirarchi F. & Mirarchi A. (2012) Development and observations of a spiny dogfish Squalus acanthias reduction device in a raised footrope silver hake Merluccius bilinearis trawl. Fisheries Research, 114, 66-75

Actions

This study is summarised as evidence for the following.

Action Category

Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water)

Action Link
Marine Fish Conservation

Fit a size-sorting escape grid (rigid or flexible) to a fish trawl net

Action Link
Marine Fish Conservation
  1. Use a different design or configuration of size-sorting escape grid/system in trawl fishing gear (bottom and mid-water)

    A replicated study in 2008–2009 of a pelagic area in the Gulf of Maine, Atlantic Ocean, USA (Chosid et al. 2012) found that changing the design of an experimental size-sorting escape grid (grid colour, orientation and position of escape vent) in a fish trawl did not typically reduce the unwanted catch of spiny dogfish Squalus acanthias between grid designs. Overall, >88% of dogfish that entered the trawl net were excluded by the size-sorting grid, regardless of grid colour or design configuration (data presented graphically). However, a black grate with an escape opening in the bottom of the trawl had a higher ratio of dogfish reduction than black top opening grids and white grids with either top or bottom openings (data not tested for statistical difference). Two fishing trials were done in the Gulf of Maine in October–November 2008 and July–August 2009 using trawl nets designed for commercial targeting of silver hake Merluccius bilinearis. The trawl nets were modified with a polyethylene grid, with 51 mm bar spacing, inserted into the extension piece in front of a small diamond mesh (51 mm) codend. Different grid colours (black and white), configurations of grid angle (35° and 45°) and location of the escape opening (top and bottom) were tested. Thirty-two valid hauls were completed. An underwater camera attached in front of the grid collected video data in 30 hauls. Dogfish escaping through the grid were recorded from review of the video data.

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

    A replicated study in 2008–2009 of two bottom fishing areas in the Gulf of Maine, USA (Chosid et al. 2012) reported that experimental rigid size-sorting escape grids fitted to a fish trawl net allowed high proportions of unwanted spiny dogfish Squalus acanthias to escape. Overall, more than 88% of spiny dogfish that entered the trawl net were excluded by size-sorting grids, regardless of grid colour or design configuration. However, a black grate with an escape opening in the bottom of the trawl was reported to show the highest dogfish escape ratio (data not tested for statistical difference). Data were collected from 32 deployments of a silver hake Merluccius bilinearis trawl during fishing trials in October–November 2008 and July–August 2009. The trawl nets were fitted with a polyethylene grid, with 51 mm bar spacing, inserted into the extension piece in front of a small diamond mesh (51 mm) codend. Different grid colours (black and white), configurations of grid angle (35° and 45°) and location of the escape opening (top and bottom) were tested. Counts of dogfish were obtained from underwater video (mounted in front of the grid) and codend catches.

Output references

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