Preprint volume - SIBM

Pre-print Volume –Posters
Topic 4: THE ELASMOBRANCHS
C. MANFREDI, E. CIAVAGLIA, C. PICCINETTI, N. VRGOČ *
Laboratory of Marine Biology and Fisheries of Fano, University of Bologna, Viale Adriatico, 1 – 16132 Fano,
Italy.
chiara.manfredi3@unibo.it
* Institute of Oceanography and Fisheries, Split.
TEMPORAL AND SPATIAL DISTRIBUTION OF SOME ELASMOBRANCHS
IN THE NORTHERN AND CENTRAL ADRIATIC SEA
DISTRIBUZIONE SPAZIO-TEMPORALE DI ALCUNI ELASMOBRANCHI
IN ALTO E MEDIO ADRIATICO
Abstract – Data collected from trawl survey, carried out in the Northern and Central Adriatic Sea, were
analysed in order to know about the spatial distribution of Myliobatis aquila, Mustelus mustelus, and
Squalus acanthias. Different distribution patterns between two seasons were detected.
Key-words: Elasmobranchs, Adriatic Sea, geographical distribution.
Introduction - Myliobatis aquila (L., 1758), Mustelus mustelus (L., 1758) and Squalus
acanthias (L., 1758) are three demersal elasmobranchs species widely distributed in the
Mediterranean. In the Adriatic Sea the smooth-hound lives on sandy and muddy-sandy
bottom of the continental shelf up to 200 m depth. The spiny dogfish lives in shallow
waters, especially at 10-200 m depth, but exceptionally it can be also found up to 900
m. The eagle ray lives on sand and soft substrates up to 100 m in depth, but most often
down to 50 m (Jardas, 1984). The aim of this work is to analyse their spatial
distribution and to consider possible seasonal changes.
Materials and methods – Data were collected in the Northern and Central Adriatic
from 2001 to 2007; in summer in the framework of the MEDITS project (Bertrand et
al., 2002) and in autumn-winter in the framework of GRU.N.D. project (Relini, 2000)
and FAO/AdriaMed Trawl Surveys Program. The sampling gear was an experimental
bottom trawl in summer surveys and an Italian commercial gear in autumn surveys. In
both surveys, the sampling design followed a depth-stratified random scheme. Catches
data were standardised per km 2 . In both seasons abundances per stratum in the three
sub-area (North Adriatic, Central Adriatic and North East Adriatic-Croatia), as
provided in the Medits project, were calculated. Statistical comparison of catches were
carried out per stratum by means of the non-parametric test of Kruskal-Wallis; in the
event of the H0 hypothesis being refused, a pairwise comparison procedure (test of
Mann-Whitney) was used to check significant differences between strata. Seasonal
distribution area was also mapped by means of geostatistical analysis using the
Indicator Kriging method. All spatial analysis and variography studies were carried out
using GStat; Arcview GIS 3.2a (Esri) was used for maps production.
Results – M. aquila was found up to 90 m depth. In summer, highest abundance
indices were estimated in the stratum 10-50 Croatia; catches in this stratum were
significantly higher respect to catches in the strata 10-50 North Adriatic and 50-100
Croatia (posthoc Mann-Withney test, p