Spatiotemporal and demographic patterns in commercial catches of tope (Galeorhinus galeus) and spurdog (Squalus acanthias)

Tope (Galeorhinus galeus) and spurdog (Squalus acanthias) have been historically overexploited by fisheries, leading to global population declines. Despite both species having well-documented migration patterns and being known to aggregate by sex and life-stage, interactions with commercial fisheries in the Northeast Atlantic have not been assessed in relation to seasonality, sex ratio and/or life-stage. Identifying and quantifying any differences would inform fisheries management efforts to mitigate the impact of overexploitation on these populations. Using reported landings and observer programme data, interactions with United Kingdom commercial fisheries on the Northwest European shelf were investigated. Both species were vulnerable to capture in setnet and bottom trawl gears, particularly in the English Channel and Celtic Sea. Recorded tope catches in the study area peaked in August (bottom trawls) and December (setnets), with no significant sex ratio bias in hauls suggesting the region is important for both sexes. For spurdog, sex-specific seasonal differences were found in the Celtic Sea in setnets with evidence of male-dominated hauls occurring further from the coast than female-dominated hauls. These results provide insights into finer scale spatio-temporal fisheries interactions for two elasmobranch populations in the Northeast Atlantic and demonstrate the utility of landings and observer programme data to identify opportunities for spatio-temporal fisheries and conservation management measures.