Spatial and temporal trends of Geryon longipes in the western Mediterranean Sea

Abstract

[eng] The deep-sea crab Geryon longipes is a by-catch species of the deep-water bottom trawl fishery targeting the red shrimp (Aristeus antennatus) in the western Mediterranean. The main objective of this work is to analyze the spatial and temporal trends of itsstandardized biomass in the western Mediterranean, from the Strait of Gibraltar to Cape Creus, including the Balearic Islands. Two data sources were used: data obtained in oceanographic surveys that are carried out annually in spring (kg/km2 ) and data of catches landed by the commercial bottom trawl fleet (kg/trip). Data analyses were carried out for the entire study zone, for each of the 12 geographical sectors considered and for the 5 areas in which they have been grouped. The results of the general models showed the same interannual increasing trend for both data sources. By sectors and areas, similar trends were also found in both data sources, but with different geographical trends. An interannual negative trend was observed in the Alboran area, the Gulf of Vera and Catalonia; conversely, a positive trend was observed in the Levantine area and the Balearic Islands. In all sectors, the highest biomass was found between 500 and 700 m. Seasonally, two peaks of high biomass were found in most of the sectors, one in spring-summer and one in early winter; however, their relative importance depends on the sector. This work is a first approach to the study of this species and more studies are still needed to identify the factors driving the opposite interannual trends found in nearby areas.