Preprint volume - SIBM

Pre-print Volume –Oral presentations
Topic 4: THE ELASMOBRANCHS
Y. ARTIOLI, E. VISENTIN 1 , A. BARAUSSE 2 , C. MAZZOLDI 1
Plymouth Marine Laboratory, Prospect Place, Western Hoe, PL1 3DH, Plymouth, UK.
1 Dept of Biology, University of Padova, Italy.
carlotta.mazzoldi@unipd.it
2 Environmental Systems Analysis Lab, University of Padova, Italy.
WHAT HISTORICAL DATA AND PREDICTIVE MODELS CAN TELL US
ABOUT ELASMOBRANCH FUTURE IN THE NORTHERN ADRIATIC
SEA
CONSIDERAZIONI SUL FUTURO DEGLI ELASMOBRANCHI NEL NORD
ADRIATICO INTEGRANDO DATI DI PESCATO E MODELLI PREDITTIVI
Abstract – With the aim to assess elasmobranch fishery status and predict future trends with different
management scenarios, in this study long term landing data (1945-2008) of Chioggia, the major fishing
fleet of the Northern Adriatic Sea, were analysed; surveys at the fish market were performed to assess
elasmobranch catch composition; an individual based model was developed for two species, Mustelus
mustelus and Scyliorhinus canicula. Landing data highlighted a dramatic decline in elasmobranch landing,
particularly for skates and Scyliorhinus spp. Landings presented periodic fluctuations, correlated in skates
with climate indices (NAO and WeMO). At present, elasmobranch composition of landing includes 13
species, with M. mustelus representing more than 60% of the total. A high proportion of landed males were
sexually immature. Model results predicted that, without management, in the next 50 years M. mustelus
population would decrease of 80%, and S. canicula of more than 90%. A management approach aimed to
protect juveniles performed far better than the fishing effort reduction. The results of this study highlight
the urgency to develop management actions for elasmobranch conservation and suggest a feasible and
promising management approach.
Key-words: shark fisheries, conservation, models.
Introduction - Elasmobranchs are exploited worldwide, and their fishery is increasing
as response to the growing demand and the accessibility of new areas to fishing boats.
Elasmobranchs are recognized to be highly vulnerable, due to their life history
characteristics (Bonfil, 1994). And indeed, even if data on elasmobranch landing and
stock status are often poor (Bonfil, 1994), several elasmobranch populations, in
particular those of large predatory species, show dramatic decline or collapse in
different areas (Dulvy et al., 2008; Ferretti et al., 2008). Moreover, elasmobranchs
often constitute bycatch of fisheries targeting other more abundant or valuable
resources (Bonfil, 1994) and, consequently they are not subject to economic extinction
prior to get close to local extinction. The decline of several elasmobranch stocks, their
high vulnerability to fishery, and the lack of data for several species and areas, call for
the improvement of international actions for the management of sharks and their
relatives. This study aims to forecast elasmobranch fishery in the Northern Adriatic Sea
(NA) analyzing and integrating: time series of landing statistics (1945-2008) from the
fish market of Chioggia; data of the present (2006-2007) elasmobranch landing
composition; results of a demographic model to predict population trends under
different management scenario based on data collected for Mustelus mustelus and
Scyliorhinus canicula.
Materials and methods – Fishing fleet consisted in 2007 of ca. 389 boats, using
different fishing gears. Official annual elasmobranch landings for the capture fisheries
of Chioggia from 1945 to 2008 were obtained from the Chioggia fish market (in
41 st S.I.B.M. CONGRESS Rapallo (GE), 7-11 June 2010
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