In this study, a grid-net design (GND) with three different bar spacings was compared with the
commercial beam trawl used in the veined rapa whelk fishery to minimize the discarded catch
amount and the loss of commercial product. In addition, the damage and mortality rates of the
species that entered the tested fishing gear were determined to understand whether the
tested fishing gear has a possible negative effect on benthic species. In the grid-net design,
a rectangular metallic grid positioned 6 cm off the ground substituted half of the codend to
allow the escape of discard species. Sea trials were carried out in the south-eastern Black
Sea between 13 and 24 October 2021. Results showed that the discarded catch amount was
significantly reduced by each GND (P < 0.05). Compared with the commercial fishing gear,
the reductions in the discarded catch amounts (in terms of number) were 91.6%, 92.2%, and
95.0% for 22, 25, and 28 mm GNDs, respectively. The minimum commercial product loss was
determined at 22 mm GND. In addition, it was seen that each GND compared to commercial
gear caused statistically significantly less damage and mortality on the discarded species. In
conclusion, 22 mm GND was the most successful design among the tested gears in
minimizing commercial product loss and reducing the discarded catch amount.
Recommendations are given for this design to be adopted by the commercial fleet.