The school of hard knocks: is the survivability of trawled-and-discarded European plaice (Pleuronectes platessa) affected by rocks in the catch? "Joanna Marie Goley"

Description

The newly reformed European Common Fisheries Policy introduced a discard ban, with an exemption of 'high likelihood of survival' species if it can be scientifically demonstrated. The commonly discarded European plaice (Pleuronectes platessa) being one of these species. To boost the survival of discarded plaice, the Belgian government necessitated beam-trawl vessels (> 221kW) to fish with a flip-up rope that excludes large stones (> 25 cm in diameter) and unwanted debris from the catch. During eight commercial beam-trawl trips on five Belgian beam trawlers between 2019 and 2020, the efficacy of the flip-up rope was assessed as well as catch composition. Two scientific observers monitored 197 deployments and assessed vitality, reflexes, injury, and on-board survival of 3195 plaice and recorded post-release survival among a sub-sample (n = 268
plaice). On-board survival was negatively related to the total catch weight and the weight of stones, both in interaction with wave height and to a lesser degree with the proportion of injury-inducing elements among the unwanted catch fraction (i.e., 10 - 20 kg sample of discards). One detailed catch comparison was conducted in December 2020, with the backboard side equipped with a flipup
rope and the other without. The use of the flip-up rope slightly improved survival: 51 % vs 44% of plaice survived 26 days after being discarded from the catch caught with vs without a flip-up rope, respectively, but this effect was not significant.

Period	2020 → 2021
Degree of Recognition	International