Spatial management of fisheries has the potential to complement selective gears to reduce unwanted catches, particularly in the context of the European Landing Obligation. This study applied spatio-temporal modelling for the first time in the Belgian beam trawl fishery to understand the taxon-specific causes and the spatio-temporal distribution of discard ratio variability. 8 species and 1 family were analyzed with Bayesian hierarchical models using observer data from 2006 to 2018. The results show that size composition of the catch and spatial variability were the most important factors in explaining discard ratio variability. The importance of taxon-specific catch, fish price variation, landing limitation restriction, and environmental factors was generally limited. The spatial structure of discards persisted over years in all taxa with seasonal variation in sole, plaice, dab, and lemon sole. Dab, plaice, lemon sole, and cod showed higher patchiness of spatial variation than that of whiting, haddock, skates, hake, and common sole. This study represents the first step towards facilitating effective spatial management of the Belgian beam trawl fishery. Further developments such as regionalized analysis, integration of fishing effort data, overlaying of taxon-specific maps, and real-time analysis could complement the current approach in developing effective spatial management strategies.
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