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RESEARCH ARTICLE

Demersal chondrichthyans in the western Mediterranean: assemblages and biological parameters of their main species

Sergio Ramírez-Amaro A B , Francesc Ordines A , Bàrbara Terrasa B , Antonio Esteban C , Cristina García D , Beatriz Guijarro A and Enric Massutí A
+ Author Affiliations
- Author Affiliations

A Instituto Español de Oceanografía, Centre Oceanogràfic de les Balears, Moll de Ponent s/n, E-07015 Palma de Mallorca, Spain.

B Laboratori de Genètica, Universitat de les Illes Balears, Carretera Valldemossa kilómetro 7.5, E-07122 Palma de Mallorca, Spain.

C Instituto Español de Oceanografía, Centro Oceanográfico de Murcia, Varadero 1, E-30740 San Pedro del Pinatar, Murcia, Spain.

D Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Muelle Pesquero s/n, E-29640 Fuengirola, Málaga, Spain.

E Corresponding author. Email: sergio.ramirez@ba.ieo.es; srgramirez08@gmail.com

Marine and Freshwater Research 67(5) 636-652 https://doi.org/10.1071/MF15093
Submitted: 3 March 2015  Accepted: 12 May 2015   Published: 6 August 2015

Abstract

The composition and structure of demersal chondrichthyan assemblages and the biological parameters of their main species were compared in four geographical subareas (GSAs) established by the General Fisheries Commission for the Mediterranean in the western Mediterranean : northern Alboran Sea (GSA01) and Alboran Island (GSA02), Balearic Islands (GSA05) and northern Spain (GSA06), with the first two being considered jointly. Data were obtained from 199 hauls undertaken from May to June 2013 during the Spanish International Bottom Trawl Survey in the Mediterranean (MEDITS). Twenty-five different chondrichthyan species were caught in all GSAs: seven were common to all areas, five appeared only in GSA01, nine appeared only in GSA05 and one appeared only in GSA06. Analysis of community structure (clusters, multidimensional scaling, analysis of similitude) revealed two assemblages related to depth, with very similar bathymetric ranges in all GSAs, namely continental shelf (from 41 to 252 m) and slope (from 284 to 813 m). The highest diversity, biomass and abundance values on the shelf and slope assemblages were recorded in GSA05 and GSA01 respectively. These results highlight the effects of the distinct fishing and oceanographic parameters related to the GSAs. Generally, the biological parameters of the most important species did not show differences between GSAs, which could suggest the existence of a single population in the western Mediterranean.

Additional keywords: abundance, bottom trawl fishery, depth-related trends, diversity, length at first maturity, vulnerable species.


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