Towards a sustainable pulse trawler fleet: insights from a spatial fishing effort allocation model of the Belgian fleet

The Belgian fishery is specialized in targeting fish species living near the seafloor or in the top layer of the sediment. To catch these demersal species, Belgian fishing vessels typically tow beam trawl fishing gear over the seafloor with heavy tickler chains rigged in the net-opening [1]. Despite its efficiency to capture high quantities of fish, conventional beam trawling with tickler chains is under pressure. First, it has a strong impact on the benthic ecosystem [2], while ecological concerns are rising. Second, fuel usage is high, while fuel prices are increasing. Third, beam trawl fisheries are highly affected by the implementation of the discard ban of the Common Fisheries Policy [3], because discard ratios of non-commercial and undersized species are high due to a poor selectivity for target species [4].

As an alternative, the EU allowed the use of the electrotrawling (pulse trawling) for a part of the beam trawler fleet active in the North Sea [5]. However, pulse trawling is successfully implemented in the Dutch fleet [6], uncertainty about the socio-economic and ecological impact obstructs the transition to pulse trawling in the Belgian fishery and obstructs the development of a pulse trawler fleet in the Belgian fishery. Hidden disincentives such as extra costs, changed catch composition, spatial interactions and quota restrictions may lead to unexpected behavior of fishermen and result in the in the so called implementation error and unintended outcomes of fisheries management [7, 8].

Within the Benthis project, the objective of this study is to find alternative management scenarios to reduce the impact of the beam trawler fishery on the benthic ecosystem. In this study, we assess the socio-economic impact of alternative pulse trawl scenarios in the Belgian fleet. Therefore, a spatially explicit fleet dynamic model is developed to study the changes in fishing effort allocation patterns of the Belgian beam trawler fleet. With this model, two possible scenarios of the current debate concerning pulse trawling in the Belgian fishery are analyzed. A scenario, whereby pulse trawlers are only allowed to fish in the North Sea, is compared with an alternative scenario whereby pulse trawlers are allowed to fish in all areas where Belgian beam trawlers have fishing rights.