Preprint volume - SIBM

Pre-print Volume –Posters
Topic 4: THE ELASMOBRANCHS
R. CARLUCCI, F. CAPEZZUTO, D. BATTISTA, M. PANZA, L. SION
Department of Animal and Environmental Biology, University of Bari Aldo Moro, Via Orabona, 4 - 70125 Bari,
Italia.
r.carlucci@biologia.uniba.it
OCCURRENCE OF JUVENILES OF SCYLIORHINUS CANICULA
AND MUSTELUS MUSTELUS IN THE NORTH-WESTERN IONIAN SEA
RINVENIMENTO DI GIOVANILI DI SCYLIORHINUS CANICULA
E MUSTELUS MUSTELUS NEL MAR IONIO SETTENTRIONALE
Abstract - Occurrence of juveniles of Scyliorhinus canicula (Chondrichthyes: Scyliorhinidae) and
Mustelus mustelus (Chondrichthyes: Triakidae) was investigated as part of trawl surveys carried out from
1994 to 2009 in the North-western Ionian Sea. Two main finding areas were observed for juveniles of S.
canicula and one of M. mustelus.
Key-words: juveniles, elasmobranchs, Scyliorhinus canicula, Mustelus mustelus, Ionian Sea.
Introduction - Elasmobranchs show slow growth rate, late age at maturity and low
fecundity, resulting highly vulnerable to overfishing as well as to the reduction and
modification of habitats in the Mediterranean Sea (Vacchi and Notarbartolo di Sciara,
2000; Serena et al., 2005). In this note, the authors provide information on the
occurrence of Scyliorhinus canicula (Linneus, 1758) and Mustelus mustelus (Linneus,
1758) juveniles in the North-western Ionian Sea.
Materials and methods - Data were collected from 1994 to 2009 in the framework of
national (GRUND) and international (MEDITS) research projects on the assessment of
demersal resources in the Mediterranean Sea (Bertrand et al., 2000; Relini et al., 2000).
The study area was the North-western Ionian Sea (GSA19). The total length (TL in
mm) was measured for S. canicula and M. mustelus providing length/frequency
distributions (LFDs). The sex was recorded and the maturity of gonads was observed
according Stehmann (1998). All the immature specimens (stage 1), with size less than
300 and 540 mm TL, were considered juveniles in S. canicula and M. mustelus
respectively, according to Capapé et al., (2008) and Saїdi et al., (2008). For both
species, the density indices (N/km 2 ) of juveniles was estimated for each sampling haul.
The spatial distribution of juveniles was carried out by means of Arcview GIS 3.2
(Esri).
Results - During the investigated period both S. canicula and M. mustelus were rarely
caught throughout the study area. The former species was captured between 115-634 m
and the latter between 12-357 m depth. The minimum and maximum sizes were
respectively 88 and 558 mm TL in S. canicula and 250 and 1620 mm TL in M.
mustelus (Fig. 1). The bulk of the sampled population consisted of juveniles (79% in
the former and 74% in the latter species). The main concentration of S. canicula
juveniles occurred with temporal continuity southward S. Maria di Leuca and Siracusa
on the upper continental slope. The maximum density value was recorded during
autumn 2003 (513 N/km 2 ). The greatest number of M. mustelus juveniles was observed
with persistency southward Catania, within 50 m depth. The maximum density value
was recorded during summer 2007 (781 N/km 2 ).
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