TY - JOUR
T1 - The effect of grid size on catch efficiency and by-catch in the demersal trawl fishery for Norway pout (Trisopterus esmarkii)
AU - Brinkhof, Jesse
AU - Grimaldo, Eduardo
AU - Herrmann, Bent
AU - Pettersen, Hermann
PY - 2022
Y1 - 2022
N2 - Norway pout (Trisopterus esmarkii) is caught with large trawls with small meshed codends, inevitably causing the fishery to have large by-catch issues. To reduce the amount of by-catch, a rigid sorting grid was made compulsory in 2010. However, there is still a severe by-catch issue, as well as the loss of target species because of the grid. A possible cause might be clogging of the grid, which could be solved by increasing the grid area. Therefore, this study compared the size selectivity of by-catch species and target species in a double-trawl configuration in which one trawl was equipped with a standard grid (6.30 m2), and the other trawl was equipped with a grid that had a 50% larger surface area (9.45 m2). The results demonstrated that the size selectivity and catch efficiency of the target species were unaffected; neither was there any significant difference between the two grids in terms of wanted by-catch species [blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), and greater argentine (Argentina silus)]. However, the larger grid caught significantly more unwanted by-catch species [haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and hake (Merluccius merluccius)]. Approximately one-third of the accumulated catches comprised the target species, one-third of wanted by-catch species, and one-third of unwanted by-catch species, demonstrating the by-catch challenges in this fishery. Simultaneously, none of the by-catch limits were exceeded.
AB - Norway pout (Trisopterus esmarkii) is caught with large trawls with small meshed codends, inevitably causing the fishery to have large by-catch issues. To reduce the amount of by-catch, a rigid sorting grid was made compulsory in 2010. However, there is still a severe by-catch issue, as well as the loss of target species because of the grid. A possible cause might be clogging of the grid, which could be solved by increasing the grid area. Therefore, this study compared the size selectivity of by-catch species and target species in a double-trawl configuration in which one trawl was equipped with a standard grid (6.30 m2), and the other trawl was equipped with a grid that had a 50% larger surface area (9.45 m2). The results demonstrated that the size selectivity and catch efficiency of the target species were unaffected; neither was there any significant difference between the two grids in terms of wanted by-catch species [blue whiting (Micromesistius poutassou), horse mackerel (Trachurus trachurus), and greater argentine (Argentina silus)]. However, the larger grid caught significantly more unwanted by-catch species [haddock (Melanogrammus aeglefinus), whiting (Merlangius merlangus), and hake (Merluccius merluccius)]. Approximately one-third of the accumulated catches comprised the target species, one-third of wanted by-catch species, and one-third of unwanted by-catch species, demonstrating the by-catch challenges in this fishery. Simultaneously, none of the by-catch limits were exceeded.
KW - Norway pout
KW - Small-meshed trawls
KW - Selectivity
KW - Grid
KW - Mixed fishery
U2 - 10.1016/j.ocecoaman.2022.106333
DO - 10.1016/j.ocecoaman.2022.106333
M3 - Journal article
SN - 0964-5691
VL - 229
JO - Ocean & Coastal Management
JF - Ocean & Coastal Management
M1 - 106333
ER -