National Institute of Aquatic Resources (DTU AQUA), Technical University of Denmark, Kgs. Lyngby, Denmark.
Danish Pelagic Producers Organisation, Copenhagen, Denmark.
PLoS One. 2024 Jul 31;19(7):e0306744. doi: 10.1371/journal.pone.0306744. eCollection 2024.
Sampling of the North Sea trawl fishery for lesser sandeel (Ammodytes marinus) showed that 96% of the catch weight consisted of the target species, and experimental sea trials demonstrated that the observed small bycatch percentages of haddock (Melanogrammus aeglefinus), mackerel (Scomber scombrus) and grey gurnard (Eutrigla gurnardus) could be significantly lowered by inserting a netting-based sorting device, an Excluder, in front of the codend. The sandeel fishery is conducted with small meshes in the codend, due to the small size and elongated body shape of this species. It is not mandatory for sandeel trawls to have any other selection devices than the small-meshed codend, and this can potentially cause problems with bycatch of unwanted species, if these are abundant on the fishing grounds. Therefore, we sampled the catch composition in this fishery and further, we compared the capture efficiency and species composition of a standard trawl, and one fitted with an additional sorting device called the Excluder. Overall, results showed small percentages of bycatch in the trips sampled and during the trials, the excluder significantly reduced the bycatches of mackerel, grey gurnard, and haddock above certain sizes. For other bycatch species results were inconclusive due to wide confidence limits affected by low bycatch numbers during the trials. The overall capture efficiency for the target species was not affected by adding the excluder in the trawl except for a significant reduction for a few semi-centimetre groups of the largest sizes of the species. These results highlight the potential of the Excluder as a bycatch reduction tool in the sandeel fishery for situations where bycatch can constitute a problem.
对北海拖网渔业中小鳞无须鳕（Ammodytes marinus）的采样表明，捕获物的 96%是目标物种，而实验性海上试验表明，鳕鱼（Melanogrammus aeglefinus）、鲐鱼（Scomber scombrus）和灰鲂（Eutrigla gurnardus）的观察到的小副渔获物比例可以通过在渔获物网前插入一个基于网的分拣装置 Excluder 显著降低。由于该物种的体型小且呈长形，因此拖网中的渔获物网眼较小。小鳞无须鳕拖网除了小网眼的渔获物网外，没有其他任何选择装置是强制性的，这可能会导致在捕捞区域，如果这些物种丰富，副渔获物中出现不需要的物种的问题。因此，我们对该渔业的渔获物组成进行了采样，并进一步比较了标准拖网和配备了称为 Excluder 的附加分拣装置的拖网的捕捞效率和物种组成。总体而言，采样的航次和试验中副渔获物的比例很小，Excluder 显著降低了超过一定大小的鲐鱼、灰鲂和鳕鱼的副渔获物。对于其他副渔获物，由于试验期间副渔获物数量低导致置信区间宽，结果不确定。在拖网中添加 Excluder 除了对该物种的几个半厘米组的最大尺寸的渔获量显著减少外，对目标物种的整体捕捞效率没有影响。这些结果突出了 Excluder 作为减少小鳞无须鳕渔业副渔获物的工具的潜力，特别是在副渔获物可能构成问题的情况下。
