Spatial distribution, life–history and fishing aspects of deep-sea silver scabbardfish Lepidopus caudatus in the Azores.
Supervisor: Regis Santos (Univ. Azores)
The deep-sea fisheries are of important economic value even though the species inhabiting there are of very low productivity. Because of this, it is necessary to generate biologically and ecologically based fishing plans to make this fishery sustainable in time. The silver scabbardfish, Lepidopus caudatus, is a worldwide distributed demersal fish, commercially exploited in the Azorean region. Several demersal species have shown declines in abundance in the Azores, but despite silver scabbardfish high landings and discharge rates in the region, information about its ecology, population structure, biology and fisheries remain unknown. This work analyzed scientific survey and fishery dependent data from the past twenty years to understand the changes in abundance and size composition. The silver scabbardfish spatial distribution was associated with depths between 200 and 400 m, latitude, and longitudes close to seamounts, islands, and sandy bottoms. The size structure varied yearly, and a bigger-deeper trend was observed. The population was dominated by females. Growth rates were between the estimated values in previous studies in the Azore, and indicated a slow grower species. The abundance indexes highlighted a declining tendency in the abundance, and this result was backed by the overexploitation status for L. caudatus in the region. Lack of management measurements and the vulnerability of L. caudatus could lead to the depletion of the resource.

Keywords: Demersal fisheries, Azores, silver scabbardfish, population structure, growth parameters.