Abstract
The aim of this study is to identify elasmobranch species present in the SouthernTyrrhenian Sea, to describe their distribution and abundance, to identify significant spatial or temporal differences between species. 14 bottom trawl surveys were carried out from 1994 to 2007. 16 species of elasmobranchs were recorded. Multidimentional Scaling Ordination (MDS) showed two groups according to the depth gradient: in the first one the stations from upper slope and in the second one the stations from middle slope. Mean biomass indices and frequency of occurrence showed that Galeus melastomus, Etmopterus spinax and Scyliorhinus canicula were the most abundant species. Mean biomass indices for other species were very low. The mean abundance of G. melastomus exhibited a positive temporal trend in biomass and density. The mean abundance of E. spinax exhibited a negative temporal trend in biomass and in density. For other species abundance varied greatly between years, even if there was no evident trend.
Highlights
In the Mediterranean Sea there is a high level of exploitation due to a great variety of fishing gears; generally the elasmobranchs are not targeted by commercial fisheries but they are an important by-catch especially of the trawl fishery and deep-water long liners [1,2,3,4]
The analysis of demersal elasmobranch species in the Southern Tyrrhenian Sea has shown that demersal elasmobranch assemblages are aligned with depth
These results are similar to those obtained in the Atlantic Ocean [15] and in the Western Mediterranean
Summary
In the Mediterranean Sea there is a high level of exploitation due to a great variety of fishing gears; generally the elasmobranchs are not targeted by commercial fisheries but they are an important by-catch especially of the trawl fishery and deep-water long liners [1,2,3,4].The decreases in abundance and biomass of some elasmobranch species throughout the last decade have been reported in the Gulf of Lions [5,6].The role of these species as indicators of fishing pressure has been suggested [4,7,8] and management strategies are necessary to minimize significantly the chondrichthyan by-catch.This paper characterizes the assemblages of demersal elasmobranch on the bottom trawl fishing grounds along the Southern Tyrrhenian Sea. The decreases in abundance and biomass of some elasmobranch species throughout the last decade have been reported in the Gulf of Lions [5,6]. The role of these species as indicators of fishing pressure has been suggested [4,7,8] and management strategies are necessary to minimize significantly the chondrichthyan by-catch. This paper characterizes the assemblages of demersal elasmobranch on the bottom trawl fishing grounds along the Southern Tyrrhenian Sea. Experimental trawl surveys are analysed for the main species in terms of species composition, community structure and distribution.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
