Preprint volume - SIBM

Pre-print Volume –Oral presentations
Topic 4: THE ELASMOBRANCHS
status. We divided the dataset between epibathyal and mesobathyal layers to identify
differences of depth in the distribution of the species, specifically among juveniles and
adults. From those data we obtained graphs of the abundance, the biomass and the
mean weight. With length measures we built a length frequency distribution to realize a
box plot graph to observe the median, the minimum and the maximum trends. Having
total lengths we choose a cut off of 25cm to identify juveniles on the basis of literature
(Tursi et al., 1993) and of the observations of modes of length frequency distributions.
Time series of all those parameters have been tested by SYSTAT programme through
the non parametric correlation Spearman test with a significance level of 0.05 and
freedom degree equal to n° of observations minus 2.
Results – The cartographic representation of abundances related to fishing points,
shows that G. melastomus is distributed mostly in the south-east part of our study area.
Specifically the population occupies the north area of the S. Lucia bank (Fig. 1), with
juveniles concentrating between 200m and 500m (Fig. 2).
Fig. 1 – Galeus melastomus. Abundance distribution of adults and juveniles. GRUND (1994-2008).
Galeus melastomus. Distribuzione dell’abbondanza degli adulti e dei giovanili. GRUND
(1994-2008).
Fig. 2 – Galeus melastomus. Abundance distribution of juveniles. GRUND (1994-2008).
Galeus melastomus. Distribuzione dell’abbondanza dei giovanili. GRUND (1994-2008).
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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