Preprint volume - SIBM

Pre-print Volume –Posters
Topic 4: THE ELASMOBRANCHS
A. GIOVE, M. MINERVA, P. MAIORANO, G. D’ONGHIA, A. TURSI
Department of Animal and Environmental Biology, University of Bari,
Via E. Orabona, 4 - 70125 Bari, Italia.
agnese.giove@gmail.com
ELASMOBRANCH ASSEMBLAGES IN THE IONIAN SEA
ASSOCIAZIONI DI ELASMOBRANCHI NEL MAR IONIO
Abstract – Multivariate analysis was applied to the abundance of elasmobranch species collected in the
Ionian Sea during eleven trawl surveys carried out from 1996 to 2008. Two main assemblages were
detected: one regarding the northern sites of the study area, almost exclusively characterized by Galeus
melastomus and Etmopterus spinax, and the other constituted by the Southern-Calabria and Eastern-
Sicilian sites, characterized by a greater number of elasmobranch species.
Key-words: Chondrichthyes, geographical distribution, multivariate analysis, Mediterranean Sea.
Introduction - In the Ionian Sea elasmobranch species have been investigated with
respect to their occurrence, depth distribution and biology (e.g. Sion et al., 2004) while
very little is known on their geographic distribution pattern. This work provides the
first contribution to the knowledge on the elasmobranch assemblages in the Ionian Sea.
Materials and methods - Data were collected between 1996 and 2008 during eleven
experimental bottom trawl surveys carried out in the North-Western Ionian Sea as part
of the GRU.N.D. program (Relini, 1998). Catch data of elasmobranches coming from
470 tows were standardized to the swept area and grouped according to geographic
zones; replicates for each site were represented by the different surveys in the resulting
density matrix (N/km 2 ). In order to reduce the effect of extreme data, the matrix was
fourth root-transformed and Bray-Curtis similarities were estimated between samples.
Non-metric Multi Dimensional Scaling ordination was applied in order to identify
groups of sites that could correspond to some geographic distribution pattern. The
ANOSIM test was applied to evaluate the differences among groups identified. The
individual species contributions to discriminate and typify the groups were examined
by means of the PRIMER SIMPER routine (Clarke and Warwick, 2001).
Results - The MDS ordination of the samples of elasmobranch abundance data
revealed the presence of two distinct groups (Fig. 1): one corresponding to the sites
located in the northern region of the study area and another constituted by the
Southern-Calabria and Eastern-Sicilian sites. The discrimination of these groups was
confirmed by ANOSIM test (R=0.82; p=0.01). The main contribution to the separation
of the identified elasmobranch assemblages was due to Galeus melastomus (63.21%
contribution to dissimilarity) followed by Etmopterus spinax (24.94%). G. melastomus
proved to be not only the major discriminator of the assemblages, but also the most
abundant species in both the assemblages, although with a different contribution to
their intra-group similarities (Fig. 1). The Southern Calabria-Sicilian assemblage, in
fact, resulted to be characterized by a greater number of elasmobranch species.
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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