Life History and Fishing Aspects of the Deep-Sea Silver Scabbardfish Lepidopus caudatus in the Azores

SIMPLE SUMMARY: The silver scabbardfish, Lepidopus caudatus, is an important demersal deep-sea species commercially exploited in the Azores archipelago. Portugal has the greatest average landings in the world with Azores being the main contributor. Unfortunately, this species has no specific measurement regulations regarding its fishing. This study aimed to fill some basic information about the species in order to further use it as a foundation for management advice. The objective was to determine the spatial distribution, life history parameters, and abundance changes using scientific survey and fishery-dependent data from 1990 to 2019. The results showed the distribution of the species was mainly associated with areas closer to islands and seamounts (200–400 m) with preference for sandy bottoms. The life history parameters exposed a slow-growing species, with a high predominance of females in the population. The abundance revealed a declining tendency, and the exploitation rate suggested the species could be slightly overexploited. Overall, this resource could be considered as vulnerable, and the parameters calculated in this study could be the basis for future works such as analytical stock assessment, to serve as a guidance for its preservation and sustainable exploitation. ABSTRACT: Deep-sea fisheries are of important economic value. Therefore, it is necessary to generate biologically and ecologically based fishing plans to make this fishery sustainable over time. The silver scabbardfish, Lepidopus caudatus, is a worldwide-distributed demersal fish, commercially exploited in the Azores. Despite L. caudatus high landings and discharges in the region, information about its ecology, population structure, biology and fisheries remains little-known. This work analyzed scientific survey and fishery-dependent data from the past 30 years to understand the changes in abundance, spatial distribution and life history of this species. Lepidopus caudatus spatial distribution was associated with depths between 200 and 400 m, close to seamounts and islands, and on sandy bottoms. The size structure varied yearly, and the population was dominated by females (sex ratio, M:F = 0.46:1). Growth rates were between the estimated values in previous studies in the Azores and indicated a slow-grower species (L(∞) = 171.62 cm, k = 0.12 year(−1), Φ’ = 3.52). The abundance indices highlighted a declining tendency, and this result was backed by the high exploitation rate for the fish in the region (E = 0.53). Lack of management measurements and the species’ vulnerability could lead to the depletion of this species.