Bycatch and incidental catch of the black scabbardfish (Aphanopus spp.) fishery off the Canary Islands

A total of 32 species were caught in surveys using Madeiran traditional longlines targeting the black scabbardfish (Aphanopus spp.) in the Canarian archipelago (northwest of Africa). Of these species, 15 belonged to the subclass Actinopterygii, 16 species to the Elasmobranchii, and one to the Holocephali. Species of the genus Aphanopus, the target species of this fishery, represented 38.5% of the catch in terms of the number of individuals and 36.4% in relation to the weight of the catch. The bycatch, which are non-target species of commercial interest, comprised only four species: two Teleostei species, Mora mora and Benthodesmus simonyi, which represented approximately 3.2% of the catch in number and 2.4% in weight; and two Elasmobranchii species, Centrophorus granulosus and Centrophorus squamosus, which represented 6.6% of the catch in number and 15.4% by weight. Deep-sea sharks were observed to be the most important component of the incidental catch (discarded species) of the traditional black scabbardfish longline fishery in the Canarian archipelago, representing 35.1% of the catch in number and 38.8% by weight. All of the Actinopterygii species were present in a proportion of less than 1%. The deep-sea shark species that were most frequent in the catches were Zameus squamulosus (44.9%), Deania hystricosa (14.7%), C. squamosus (13.5%), Centroscymnus coelolepis (6.7%) and Etmopterus princeps (5.1%). The ratio between the commercial catch (targeted species and bycatch) and the incidental catch was 1:1 in number of individuals. The ratio between the catch of the target species and the deep-sea sharks was 1:1 in number of individuals and in weight. The proportion of immature sharks constituted 31.7% of the total of all sharks caught.