Using High‐Resolution Fisheries Data to Identify Spatial Patterns in Retained Catch Compositions for Mixed Fisheries

ABSTRACT Mixed fisheries exploit fish stocks that are heterogeneously distributed in space using gears that are not species selective. This poses a challenge for management as catch limits for less productive stocks constrain catches of more productive stocks leading to losses in yield and economic value. Decoupling catches of stocks caught together in mixed fisheries could increase potential yields and may be achieved through changes in spatial fishing patterns. This study identifies fine‐scale spatial patterns of retained catches for the UK otter trawlers in UK waters by combining vessel monitoring system positional information and logbook data on retained catches. Spatially contiguous units were identified through a combination of Principal Components Analysis and spatial clustering. Our results show a complex spatial structure in the fish assemblage which differs across UK sea areas, with greater similarity between the Northern North Sea and West of Scotland compared to other sea areas. Through simulation, we highlight how fine‐scale spatially resolved fisheries data can identify areas where choke risks from catches of low‐quota, low‐productivity species associated with target species can be reduced. This underscores the value of fine‐scale data for enhancing efficiency and sustainability in mixed fisheries. Wider benefits from the use of fine‐scale data include the ability to identify consistent spatial métier definitions for use in modelling technical interactions. Ultimately, our study informs strategies and approaches that decouple catches of low‐quota, low‐productivity species caught together in mixed fisheries, improving sustainability and the conservation of living resources under complex management challenges.