Two sympatric, not externally discernible, and heavily exploited deepwater species with coastal migration during spawning season: implications for sustainable stocks management of Aphanopus carbo and Aphanopus intermedius around Madeira

Abstract

Several artisanal fisheries target deepwater species. These stocks are highly sensitive to overfishing because of their slow growth and late maturation. This vulnerability is higher if species concentrate during spawning season in coastal areas, as occur with scabbardfish (Aphanopus spp.). In this paper, we explore if two Aphanopus species (A. carbo and A. intermedius) that coexist show migration patterns to coastal areas during spawning. We analysed specimens of both species throughout 4 years (2014–2017) in a weekly basis and compare morphological parameters with the distance of the coast (coastal (<12 n.m.; 1 n.m. = 1.852 km) versus offshore (>12 n.m.)). Both species showed coastal patterns of migration during the spawning season (October– December), with 65.90% of total specimens of A. carbo and 51.60% of A. intermedius being caught at <12 n.m. during this season. Fishing events were also more numerous at <12 n.m. to the coast during spawning season (46.6%) relative to nonspawning season (32.6%). A series of management measures (e.g., October–December season) were developed to preserve Aphanopus stocks in the Northeast Atlantic Ocean.