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The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains over 3000 records (more than 4000 individuals) of large elasmobranch species from 20 different countries around the Mediterranean and Black seas, observed from 1666 to 2017. The main species included in the archive are the devil fish (1 813 individuals), the basking shark (939 individuals), the blue shark (585 individuals) and the great white shark (337 individuals).In the last decades other species such as the shortfin mako (166 individuals), the spiny butterfly ray (138) and the thresher shark (174 individuals) were reported with an increasing frequency. This was possibly due to an increased public awareness on the conservation status of sharks, and a consequent development of new monitoring programmes. MEDLEM does not have a homogeneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the northern sectors and the absence in our database of some species does not imply their actual absence in these regions. Some considerations are made on the frequency and spatial distribution of records, size structure of the observed individuals for selected species, general area coverage and species involved as by-catch by fishing gear.
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Mediterranean Marine Science
Vol. 0
MEDLEM database, a data collection on large
Elasmobranchs in the Mediterranean and Black seas
MANCUSI CECILIA Environmental Protection
Agency (ARPAT)
BAINO ROMANO Environmental Protection
Agency (ARPAT)
FORTUNA CATERINA Italian Institute for
Environmental Protection
and Research (ISPRA)
DE SOLA LUIS GIL IEO
MOREY GABRIEL Balearic Islands Government
BRADAI MOHAMED
NEJMEDDINE
INSTM
KALLIANOTIS ARGYRIOS N.AG.RE.F
SOLDO ALEN University of Split
HEMIDA FARID USTHB
SAAD ADIB ALI Tishreen University
DIMECH MARK Food and Agriculture
Organization of the United
Nations (FAO)
PERISTERAKI PANAGIOTAHellenic Center for Marine
Research
BARICHE MICHEL American University of Beirut
CLÒ SIMONA Medsharks
DE SABATA ELEONORA Medsharks
CASTELLANO LAURA Aquarium of Genoa
GARIBALDI FULVIO University of Genoa
LANTERI LUCA University of Genoa
TINTI FAUSTO University of Bologna
PAIS ANTONIO University of Sassari
SPERONE EMILIO University of Calabria
MICARELLI PRIMO Aquarium of Massa
Marittima
POISSON FRANCOIS MARBEC, Univ. Montpellier,
CNRS, Ifremer, IRD
SION LETIZIA University of Bari
CARLUCCI ROBERTO University of Bari
CEBRIAN-MENCHERO
DANIEL
RAC-SPA
SÉRET BERNARD Ichtyo Consult
FERRETTI FRANCESCO Hopkins Marine Station of
Stanford University
EL-FAR ALAA National Institute of
Oceanography and Fisheries
(NIOF)
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SAYGU ISMET
SHAKMAN ESMAIL University of Tripoli
BARTOLI ALEX SUBMON – Marine
Environmental Services
GUALLART JAVIER University of Valencia
DAMALAS DIMITRIOS Hellenic Center for Marine
Research
MEGALOFONOU
PERSEFONI
University of Athens
VACCHI MARINO ISMAR (Institute of Marine
Sciences, National Research
Council
BOTTARO MASSIMILIANO Stazione Zoologica Anton
Dohrn
NOTARBARTOLO DI
SCIARA GIUSEPPE
Tethys Research Institute
FOLLESA MARIA
CRISTINA
University of Cagliari
CANNAS RITA University of Cagliari
KABASAKAL HAKAN Ichthyological Research
Society
ZAVA BRUNO Wilderness Environmental
Studies
CAVLAN GRAZIELLA Nature Trust
JUNG ARMELLE Des Requins et Des
Hommes
ABUDAYA MOHAMMED National Research Centre
(Gaza-Palestine)
KOLITARI JERINA University of Tirana
BARASH ADI University of Haifa
JOKSIMOVIC
ALEKSANDAR
University of Montenegro
MARČETA BOJAN Fisheries Research Institute
GONZALEZ VILAS LUIS University of Vigo
TIRALONGO FRANCESCO University of Catania
GIOVOS IOANNIS iSea & Marine and
Environmental Research
(MER)
BARGNESI FILIPPO Marche Polytechnic
University, Ancona &
Cattolica aquarium,
Cattolica, RN, Italy,
LELLI STEFANO Food and Agriculture
Organization of the United
Nations, EastMed Project
BARONE MONICA Food and Agriculture
Organization of the United
Nation, Fisheries Resources
Consultant
MORO STEFANO Sapienza University of Rome
MAZZOLDI CARLOTTA University of Padova
CHARIS CHARILAOU DFMR - Department of
Fisheries and Marine
Research
ABELLA ALVARO JUAN Institute for Marine Biological
Resources and
Biotechnologies (IRBIM),
National Research Council –
(CNR)
SERENA FABRIZIO Institute for Marine Biological
Resources and
Biotechnologies (IRBIM),
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National Research Council –
(CNR)
https://doi.org/10.12681/mms.21148
Copyright © 2020 Mediterranean Marine Science
To cite this article:
MANCUSI, C., BAINO, R., FORTUNA, C., DE SOLA, L., MOREY, G., BRADAI, M., KALLIANOTIS, A., SOLDO, A.,
HEMIDA, F., SAAD, A., DIMECH, M., PERISTERAKI, P., BARICHE, M., CLÒ, S., DE SABATA, E., CASTELLANO, L.,
GARIBALDI, F., LANTERI, L., TINTI, F., PAIS, A., SPERONE, E., MICARELLI, P., POISSON, F., SION, L., CARLUCCI,
R., CEBRIAN-MENCHERO, D., SÉRET, B., FERRETTI, F., EL-FAR, A., SAYGU, I., SHAKMAN, E., BARTOLI, A.,
GUALLART, J., DAMALAS, D., MEGALOFONOU, P., VACCHI, M., BOTTARO, M., NOTARBARTOLO DI SCIARA, G.,
FOLLESA, M., CANNAS, R., KABASAKAL, H., ZAVA, B., CAVLAN, G., JUNG, A., ABUDAYA, M., KOLITARI, J.,
BARASH, A., JOKSIMOVIC, A., MARČETA, B., GONZALEZ VILAS, L., TIRALONGO, F., GIOVOS, I., BARGNESI, F.,
LELLI, S., BARONE, M., MORO, S., MAZZOLDI, C., CHARIS, C., ABELLA, A., & SERENA, F. (2020). MEDLEM
database, a data collection on large Elasmobranchs in the Mediterranean and Black seas. Mediterranean Marine
Science, 0, 276-288. doi:https://doi.org/10.12681/mms.21148
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276 Medit. Mar. Sci., 21/2 2020, 276-288
Mediterranean Marine Science
Indexed in WoS (Web of Science, ISI Thomson) and SCOPUS
The journal is available on line at http://www.medit-mar-sc.net
DOI: http://dx.doi.org/10.12681/mms.21148
Research Article
MEDLEM database, a data collection on large Elasmobranchs in the Mediterranean
and Black seas
Cecilia MANCUSI1, Romano BAINO1, Caterina FORTUNA2, Luis Gil DE SOLA3, Gabriel MOREY4,
Mohamed NEJMEDDINE BRADAÏ5, Argyrios KALLIANOTIS6, Alen SOLDO7, Farid HEMIDA8, Adib Ali
SAAD9, Mark DIMECH10, Panagiota PERISTERAKI11, Michel BARICHE12, Simona CLÒ13, Eleonora DE
SABATA13, Laura CASTELLANO14, Fulvio GARIBALDI15, Luca LANTERI15, Fausto TINTI16, Antonio PAIS17,
Emilio SPERONE18, Primo MICARELLI19, Francois POISSON20, Letizia SION21, Roberto CARLUCCI21, Daniel
CEBRIAN-MENCHERO22, Bernard SÉRET23, Francesco FERRETTI24, Alaa EL-FAR25, Ismet SAYGU26, Esmail
A. SHAKMAN27, Àlex BARTOLÍ28, Javier GUALLART29, Dimitrios DAMALAS11, Persefoni MEGALOFONOU30,
Marino VACCHI31, Francesco COLLOCA32, Massimiliano BOTTARO32, Giuseppe NOTARBARTOLO DI
SCIARA33, Maria Cristina FOLLESA34, Rita CANNAS34, Hakan KABASAKAL35, Bruno ZAVA36, Graziella
CAVLAN37, Armelle JUNG38, Mohammed ABUDAYA39, JERINA KOLITARI40, ADI BARASH41, ALEKSANDAR
JOKSIMOVIC42, ILIJA CETKOVIC42, BOJAN MARČETA43, LUIS GONZALEZ VILAS44, Francesco
TIRALONGO45, Ioannis GIOVOS46, Filippo BARGNESI47, Stefano LELLI48, Monica BARONE49, Stefano
MORO50, Carlotta MAZZOLDI51, Charilaou CHARIS52, Alvaro JUAN ABELLA53 and Fabrizio SERENA53
1 Environmental Protection Agency, ARPAT, Italy, 2 Italian Institute for Environmental Protection and Research, ISPRA, Italy, 3
IEO, Spain, 4 Balearic Islands Government, Spain, 5 INSTM, Tunisia, 6 N.AG.RE.F., Greece, 7 University of Split, Croatia, 8 USTHB,
Algeria, 9 Tishreen University, Syria, 10 Food and Agriculture Organization, 11 Hellenic Center for Marine Research, Greece, 12 American
University of Beirut, Lebanon, 13 Medsharks, Italy, 14 Aquarium of Genoa, Italy, 15 University of Genoa, Italy, 16 University of Bologna,
Italy, 17 University of Sassari, Italy, 18 University of Calabria, Italy, 19 Aquarium of Massa Marittima, Italy, 20 MARBEC, Univ. Mont-
pellier, CNRS, Ifremer, IRD, France, 21 University of Bari, Italy, 22 RAC-SPA, Tunisia, 23 Ichtyo Consult, France, 24 Department of Fish
& Wildlife Conservation, Virginia Tech. USA, 25 National Institute of Oceanography and Fisheries, Egypt, 26 University of Cukurova,
Turkey, 27 University of Tripoli, Libya, 28 SUBMON – Marine Environmental Services, Spain, 29 University of Valencia, Spain, 30 Uni-
versity of Athens, Greece, 31 Institute of Marine Sciences, National Research Council, Italy, 32 Stazione Zoologica Anton Dohrn, Italy, 33
Tethys Research Institute, Italy, 34 University of Cagliari, Italy, 35 Ichthyological Research Society, Turkey, 36 Wilderness Environmental
Studies, Italy, 37 Nature Trust, Malta, 38 Des Requins et Des Hommes, France, 39 National Research Centre, Gaza-Palestine, 40 University
of Tirana, Albania, 41 University of Haifa, Israel, 42 University of Montenegro, Montenegro, 43 Fisheries Research Institute, Slovenia,
44 University of Vigo, Spain, 45 University of Catania, Italy, 46 iSea & Marine and Environmental Research, MER, Greece & Cyprus, 47
Marche Polytechnic University, Ancona, Italy, 48 Food and Agriculture Organization of the United Nations, EastMed Project, Italy, 49
Food and Agriculture Organization of the United Nation, Fisheries Resources Consultant, Italy, 50 Sapienza University of Rome, Italy,
51 University of Padova, Italy, 52 DFMR - Department of Fisheries and Marine Research, Cyprus, 53 Institute for Marine Biological
Resources and Biotechnologies, IRBIM, National Research Council, Italy
Corresponding author: fabrizio.serena@irbim.cnr.it
Handling Editor: Argyro ZENETOS
Received: 10 September 2019; Accepted: 1 April 2020; Published on line: 10 May 2020
Abstract
The Mediterranean Large Elasmobranchs Monitoring (MEDLEM) database contains more than 3,000 records (with more than
4,000 individuals) of large elasmobranch species from 21 different countries around the Mediterranean and Black seas, observed
from 1666 to 2017. The principal species included in the archive are the devil ray (1,868 individuals), the basking shark (935
individuals), the blue shark (622 individuals), and the great white shark (342 individuals).
In the last decades, other species such as the thresher shark (187 individuals), the shortfin mako (180 individuals), and the
spiny butterfly ray (138) were reported with increasing frequency. This was possibly due to increased public awareness on the
conservation status of sharks, and the consequent development of new monitoring programs. MEDLEM does not have homo-
geneous reporting coverage throughout the Mediterranean and Black seas and it should be considered as a database of observed
species presence. Scientific monitoring efforts in the south-eastern Mediterranean and Black seas are generally lower than in the
northern sectors and the absence of some species in our database does not imply their actual absence in these regions. However,
the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected
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Medit. Mar. Sci., 21/2, 2020, 276-288
the available data allowed us to analyse the frequency and spatial distribution of records, the size frequencies for a few selected
species, the overall area coverage, and which species are involved as bycatch by different fishing gears.
Keywords: Bycatch; databases; geographical distribution; large elasmobranchs; Mediterranean and Black seas; sharks.
Introduction
Even if the Mediterranean Sea covers approximately
1% of the planet’s ocean surface, it displays a relatively
high fish diversity, with approximately 3-4% of the en-
tire world’s fish species inhabiting its waters (Fredj et al.,
1992; Groombridge & Jenkins, 2002). In particular, the
chondrichthyan richness is particularly high with 7% of
the total number of cartilaginous fishes represented in-
side the basin (Compagno, 1984a; Compagno, 1984b;
Séret & Serena, 2002; Last et al., 2016; Serena, 2005;
FAO, 2018a; FAO, 2018b). Despite this high biodiver-
sity, the Mediterranean Sea shows greater conservation
concern for chondrichthyans than the rest of the world, as
reported by the last IUCN Regional Red List assessment,
which listed more than half of the 73 evaluated species
as threatened (Dulvy et al., 2016). In addition, after ten
years since the first assessment, 13 species are still con-
sidered data deficient, indicating large knowledge
and data gaps characterising this geographic area
(Walls & Dulvy, 2020).
Due to their life history characteristics, sharks and
rays are particularly susceptible to over-exploitation and
their populations have very low resilience. Species often
show restricted distributions and small population sizes,
dependent on mating, spawning, nursery, and breeding
grounds or specific habitats (Stevens et al., 2000; Sere-
na, 2005). In general, cartilaginous fish are exploited for
fins, skin, jaws, and meat. Sometimes they are a direct
target of commercial and recreational fisheries while in
other cases they are incidentally caught as bycatch. In
many areas of the world a decline in cartilaginous fish
landings has been observed, while fishing effort has gen-
erally increased (Heithaus et al., 2008; McPhearson &
Myers, 2009; Davidson et al., 2016). The global capture
of sharks and rays reported to the Food and Agriculture
Organization of the United Nations increased to a peak
in 2003 and subsequently declined by 20% (Dulvy et al.,
2014).
Since 2010, the General Fisheries Commission for the
Mediterranean (GFCM) adopted measures to reduce by-
catch rates and, after that, a reduction in sharks and rays
landings has been observed in the Mediterranean area
(FAOc, 2018). However, there is no evidence that the dis-
card of these species has also been reduced. Moreover,
many countries reported shark statistics without making
any distinction at the species level or even not recording
some species at all. The inadequate collection of landing
information in many areas makes it difficult to quantify
the impact of fishing drawdown.
Large cartilaginous fishes are mostly pelagic and
highly migratory species not closely associated with the
seabed but living primarily in the open seas, away from
continental shelves. Their highly migratory nature and
their behaviour generally do not reflect environmental
boundaries. In the Mediterranean, both life-history traits
and a very low catch rate resulted in several issues for
the collection of robust scientific data. The most common
monitoring schemes usually fail to reveal large pelagic
shark occurrences and data collection is not supported by
standardised assessment procedures (Damalas & Mega-
lofonou, 2012). Although there is no real direct fishery
targeting large cartilaginous fishes in the Mediterranean
and Black seas, they are incidentally caught mainly
by gillnets and longlines. In contrast, benthic rays and
some smaller sharks, such as the smooth-hound and cat-
sharks, constitute a lower bycatch portion in these fishing
gears, whilst they are often important bycatches of the
bottom-trawl and small-scale fisheries, widely operat-
ing throughout the basin. Large elasmobranchs are also
caught by bottom longlines targeting European hake. The
surface drifting longlines, targeting tuna and swordfish,
also capture some pelagic shark species as bycatches or
discards (Bonfil, 2002; Mejuto et al., 2002; Peristeraki
et al., 2008; Damalas & Megalofonou, 2012; Garibaldi,
2015; Poisson et al., 2016).
In the Mediterranean area, the basking shark (Cetorhi-
nus maximus), the devil ray (Mobula mobular), and the
great white shark (Carcharodon carcharias) have been
historically recognised as the species that require the
most protection. Although they are not directly targeted
by any Mediterranean fishery except, perhaps, the devil
ray in the Gaza Strip (Palestine), they have been includ-
ed in several conventions related to conservation of ma-
rine living resources: Barcelona Convention Protocol on
Specially Protected Areas and Biological Diversity (SPA/
BD) in the Mediterranean (all three species are listed in
Appendix II), Bern Convention, on Appendix II of the
Convention on International Trade in Endangered Spe-
cies (CITES), and in some national and EU regulations.
To face the biodiversity loss and to increase the ef-
fectiveness of the conservation measures in the Med-
iterranean basin, it is important to establish a common
procedure to collect data on shark specimens that are acci-
dentally captured, sighted at sea or stranded. In this light,
the MEDLEM database (Mediterranean Large Elasmo-
branchs Monitoring) aims at contributing to the improve-
ment of knowledge on the presence, spatial distribution,
and bycatch of large elasmobranch species present in the
Mediterranean and Black seas. Hence, it may represent a
useful tool for national and international organisations in-
volved in the biodiversity management and conservation
of this important semi-enclosed basin (e.g., the Food and
Agriculture Organization/General Fisheries Commission
for the Mediterranean (FAO-GFCM), the United Nations
Environment Programme/Mediterranean Action Plan and
IUCN SSC Shark Specialist Group, and the European
Community Action Plan).
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278 Medit. Mar. Sci., 21/2 2020, 276-288
In more detail, the main aims of the MEDLEM pro-
gramme are (1) collecting information on bycatch, sight-
ing, and stranding events throughout the Mediterranean
and Black seas, (2) establishing a common protocol,
and (3) recording their spatial occurrence (Serena et al.,
2014). As an additional goal, MEDLEM stores scientific
papers related to elasmobranchs in the Mediterranean and
Black seas as well as any reliable information from news-
papers and social media.
Established officially in 1985 (Mancusi & Serena,
2014), it became fully operational in 2000, beginning to
record data on elasmobranchs catches, sightings, strand-
ings, and historical records within a single database
(Ben-Tuvia, 1971; Boero & Carli, 1979; Biagi, 1995;
Megalofonou et al., 2000; Lipej et al., 2000; Bradaï et
al., 2002; Barrul & Mate, 2002; Soldo & Jardas, 2002a;
Soldo & Jardas, 2002b; Morey & Massuti, 2003; Kaba-
sakal, 2004; Morey et al., 2006; Morey et al., 2008; Ali
& Saad, 2010; Kabasakal & De Maddalena, 2011; Kaba-
sakal, 2013a; Kabasakal, 2013b; Carlucci et al., 2014).
The MEDLEM programme directly links up with the
FAO IPOA-Sharks and it was submitted to the discussion
of the SAC Sub-Committee on Marine Environment and
Ecosystems (SCMEE) of the GFCM, Scientific Adviso-
ry Committee on Fisheries (SAC) (Barcelona, 6-9 May
2002) as “subproject Basking shark”. At the meeting of
the SCMEE in Spain (Malaga, 10-12 May 2004), a com-
mon protocol for collecting field data was proposed and
many Mediterranean countries showed the will to coop-
erate with this initiative and to conform to a standardised
data collection framework. At the seventh session of the
GFCM (Rome, 19-22 October 2004), the SCMEE reit-
erated the importance of wider uses of the MEDLEM
protocols and information system, already adopted by
several regional bodies, to favour the timely exchange of
information on large elasmobranchs (FAO, 2005; Sere-
na et al., 2008; Serena et al., 2009). The MEDLEM pro-
gramme has also been presented at the European Elas-
mobranch Association annual conference (Mancusi et al.,
2005), the IUCN (Cavanagh & Gibson, 2007), and RAC-
SPA (UNEP, 2009) meetings.
Materials and Μethods
Study area
The Mediterranean Sea covers ca. 2,500,000 km2,
with 23 countries bordering its more than 45,000 km of
coastline (EU, 2010). The basin spans from the Straits of
Gibraltar to the Middle East for ca. 4000 km, reaching
its maximum depth (5,267 m) in the eastern Ionian Sea
(Calypso Pit) (Barale, 2008). The Mediterranean Sea can
be roughly divided into two main sub-basins, the west-
ern and the eastern Mediterranean, separated by the Sic-
ily-Tunisia ridge. The eastern basin is characterised by
a higher oceanographic variability of SSTs (Sea Surface
Temperatures) ranging between 17.82°C during winter
and 29.71°C during the warmest months (Poulos et al.,
1997; Abboud Abi Saab et al., 2013) and, also, a higher
average salinity (39‰). By contrast, the western basin is
generally cooler and relatively less salty, with an aver-
age sea surface temperature of 12°C during winter, 23°C
during summer, and an average salinity of ca. 36‰ (Ser-
ena, 2005).
The MEDLEM database
The main features of the MEDLEM Database Appli-
cation are: (i) the implementation of data collection, es-
pecially for bycatch evaluation; (ii) the standardisation of
data entry procedures; (iii) effective data sharing among
the participating countries, and (iv) free access for par-
ticipants to the web site. The database was initially cre-
ated in Oracle. Recently, the application has been writ-
ten with Apache/Perl technology, allowing interfaces to
a MySQL database (version 3.23.58); a migration from
MySQL to Oracle has been necessary using the technol-
ogy Zope/Plone or Apache/PHP (Serena et al., 2006).
The MEDLEM database is organised as shown in Table
1. The protocol characterises the word “large”, which
defines the nature of the database (Mediterranean Large
Elasmobranchs Monitoring database). This refers to the
Table 1. Structure of the MEDLEM database.
Documentation of the archive Contents of the documentation
BIBLIOGRAPHIES Bibliographic references
BIOLOGICAL_PARAMETERS Biological parameters (length, weight, sex, biometrics, etc.), if known, of the species
insert in the database
GEARS List of the fishing gears responsible for captures
SPECIES_DATA Spatio-temporal data about catches, strandings or sightings (data, time, country,
latitude, longitude, etc.);
SPECIES_LIST List of all the species captured/sighted/stranded
USERS Details of the users of the application
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Medit. Mar. Sci., 21/2, 2020, 276-288
maximum size reached by each different species: we only
consider sharks with more than 100 cm in total length
(TL) and batoids with more than 150 cm in disc width
(DW) (Serena et al., 2014). Applying this rule to our spe-
cies in the Mediterranean and Black seas, we restricted
for MEDLEM protocol the families listed in Table 2.
Thanks to the collaboration of several research in-
stitutes, military authorities, and professional and recre-
ational fishermen a great amount of valuable information
on catches, sightings, and strandings of large cartilagi-
nous fishes has been archived into the MEDLEM da-
tabase. Furthermore, the database gathered significant
observations derived from social media, particularly
Facebook and YouTube, with some videos and images
allowing species identification. Thanks to the support
of Facebook pages and citizen science platforms such as
the “Mediterranean marine life” Facebook group, Shark-
Pulse, the “Gruppo Ricercatori Italiani sugli Squali, raz-
ze e chimere (GRIS)”, the SharksStudiesCenter, etc., we
have been able to obtain valid data. Currently all infor-
mation is collected by the medlemcontact@gmail.com
account or directly on the field.
A data quality check is carried out on all newly re-
ceived information. Unconfirmed information is discard-
ed, and duplicated data is eliminated. The data collected
allowed us to create records distribution maps for the most
significant species, mad possible using a software called
ModestR, which supports arranged databases in provid-
ing features to clean, manage, and analyse large species
distribution datasets (García-Roselló et al., 2014).
Finally, to take into account biases related to dif-
ferences in reporting rates between different historical
periods, occurrence rates (specimens per year), were
measured considering three different periods, arbitrari-
ly designated: 1800‒1865; 1866‒1985 and 1986‒2017.
During the first period, named “ancient”, events such as
catches, sightings, etc., were reported in literature occa-
sionally and ancillary information was absent or rarely
included in the report. During the successive period, up
to approximately 1985, even if several occurrences were
recorded, they were often collected in a non-systematic
manner, and with information quality and details depend-
ing only on the scientists’ skills. In the most recent times,
many better-defined monitoring programs have been ac-
tivated, including MEDLEM, which unofficially record-
ed events as early as 1975. Previous recordings quoted in
1666 have been considered just as general information.
As part of this program and thanks to the creation of an
information network in the Mediterranean, it was possible
to acquire more and higher quality information, although
actual effort cannot guarantee complete spatio-tempo-
ral coverage and some occurrences are likely to still be
lost. The amount of information collected in MEDLEM
allowed us to carry out a first preliminary assessment of
the elasmobranch bycatch in the Mediterranean as well
as to enhance our knowledge of many biological aspects
of some species. Indeed, due to these records, it was pos-
sible to estimate the length-weight relationships and the
length-frequency distributions for some Mediterranean
elasmobranch species.
Results and Discussion
The data recorded into the MEDLEM database and
presented here refer to the period from 1666 to 2017. The
archive contains a total of 4,963 specimens correspond-
ing to 3,197 records, obtained from various research in-
stitutes belonging to 21 different countries. The higher
number of records are mainly from Italy (2,248 records)
followed by Palestine (1,084 records, almost entirely
matching to exceptional M. mobular catches), Greece
(301), Spain (286), Croatia (225), Turkey (159), Egypt
(128), France (126), Syria (115), Malta (93), Tunisia (68),
followed by the other countries (Fig. 1A).
The MEDLEM database includes 34 species and 2
categories (group of species) belonging to 16 different
families and 7 orders (Tab. 2). The most frequent species
reported is the devil ray (M. mobular) holding 37.6% of
the total number of records, followed by the basking shark
(C. maximus, 18.8%), the blue shark (Prionace glauca,
12.5%), the great white shark (C. carcharias, 6.9%), the
thresher shark and bluntnose sixgill shark (Alopias vulpi-
nus and Hexanchus griseus each with 3.8%), the shortfin
mako (Isurus oxyrinchus, 3.6%), and the spiny butterfly
ray (Gymnura altavela, 2.8%). All the other species ac-
count for ca. 9% of the available records (Fig. 1B). The
highest occurrence of M. mobular records is ascribed to
two specific events in March 2006 and February 2013, in
which 279 and 299 specimens were landed in Gaza Strip
(Levantine Sea) by a local purse seine, called “shinshu-
la”, and then slaughtered on the beach and used as food
(Abudaya et al., 2017). Remarkably, it seems that the lo-
cal fishery directly targeting Mobula has been operating
in the area throughout the years, passing unnoticed until
those events were reported (Cebrian, pers. comm.).
Other records in the database refer to less (I. oxyrin-
chus, G. altavela, A. vulpinus, H. griseus) or rarely ob-
served species (Alopias superciliosus, Sphyrna zygaena,
Squatina squatina, and Squatina oculata). Among the
rarely sighted species, some observations can be consid-
ered as the first record of the species in the Mediterranean
Sea: Sphyrna mokarran (Boero & Carli, 1977) and the
recently well-documented first occurrence of Galeocerdo
cuvier (Tobuni et al., 2016). Furthermore, some records
reported the first observation of a species in national wa-
ters, such as Taeniurops grabatus in Italy and Syria (Ser-
ena et al., 1999a; Ali et al., 2013) and Himantura uarnak
in Syria (Ali et al., 2010). The database also includes
some questionable records of Sphyrna tudes. This spe-
cies was initially described in the Mediterranean Sea by
Tortonese (1951) and later confirmed by McEachran &
Séret (1987), but needs confirmation.
Regarding the occurrence rates from 1800 to 1865, the
average was 1.7 specimens/year, which increased to 5.3
specimens/year in the second period (1866-1985), based
mainly on bibliographic sources. In the last 32 years
(1986-2017), the recording rate has further increased to
87.3 specimens/year (Fig. 1E). However, this increase is
likely to be attributed to the increased scientific commu-
nity attention towards elasmobranchs and both the high-
er abilities and efforts attained in the identification and
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280 Medit. Mar. Sci., 21/2 2020, 276-288
Table 2. List of the orders, families and species recorded in the MEDLEM database. IUCN Categories are also considered (CR, Critically
Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; LC, Least Concern; DD, Data Deficient; NE: Not Evaluated).
Group Order Family Scientic name Common name
IUCN
Cate-
gories
In-
divi-
duals
%
Batoid MYLIOBATOFORMES Mobulidae Mobula mobular Devil ray EN 1868 37,6
Shark LAMNIFORMES Cetorhinidae Cetorhinus maximus Basking shark EN 935 18,8
Shark CARCHARHINIFORMES Carcharhinidae Prionace glauca Blue shark CR 622 12,5
Shark LAMNIFORMES Lamnidae Carcharodon carcha-
rias Great white shark CR 342 6,9
Shark HEXANCHIFORMES Hexanchidae Hexanchus griseus Bluntnose sixgill shark LC 189 3,8
Shark LAMNIFORMES Alopiidae Alopias vulpinus Thresher shark EN 187 3,8
Shark LAMNIFORMES Lamnidae Isurus oxyrinchus Shortfin mako CR 180 3,6
Batoid MYLIOBATOFORMES Gymnuridae Gymnura altavela Spiny buttery ray CR 138 2,8
Shark SQUALIFORMES Echinorhinidae Echinorhinus brucus Bramble shark EN 76 1,5
Batoid MYLIOBATOFORMES Dasyatidae Dasyatis pastinaca Common stingray VU 69 1,4
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus plum-
beus Sandbar shark EN 57 1,1
Shark CARCHARHINIFORMES Triakidae Galeorhinus galeus Tope shark VU 51 1,0
Shark LAMNIFORMES Alopiidae Alopias superciliosus Bigeye thresher shark EN 37 0,7
Batoid RAJIFORMES Rajidae Rostroraja alba White skate EN 37 0,7
Shark LAMNIFORMES Lamnidae Lamna nasus Porbeagle CR 27 0,5
Shark SQUALIFORMES Squatinidae Squatina aculeata Sawback angelshark CR 26 0,5
Batoid RAJIFORMES Rajidae Raiformes Raja rays nei 22 0,4
Shark CARCHARHINIFORMES Sphyrnidae Sphyrna zygaena Smooth hammerhead CR 21 0,4
Shark HEXANCHIFORMES Hexanchidae Heptranchias perlo Sharpnose sevengill
shark DD 10 0,2
Shark LAMNIFORMES Odontaspididae Odontaspis ferox Smalltooth sand tiger CR 10 0,2
Shark SQUALIFORMES Squatinidae Squatina oculata Smoothback angelshark CR 10 0,2
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus ob-
scurus Dusky shark DD 9 0,2
Batoid RHINOPRISTIFORMES Rhinobatidae Rhinobatos rhino-
batos Common guitarfish EN 7 0,1
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus bra-
chyurus Copper shark DD 6 0,1
Shark SQUALIFORMES Squatinidae Squatina squatina Angelshark CR 6 0,1
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus spp Carcharhinus sharks nei 5 0,1
Batoid MYLIOBATOFORMES Myliobatidae Aetomylaeus bovinus Bull ray CR 3 0,1
Shark CARCHARHINIFORMES Carcharhinidae Galeocerdo cuvier Tiger shark NE 3 0,1
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus falci-
formis Silky shark NE 2 0,0
Shark CARCHARHINIFORMES Sphyrnidae Sphyrna tudes Smalleye hammerhead NE 2 0,0
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus brevi-
pinna Spinner shark NE 1 0,0
Shark CARCHARHINIFORMES Carcharhinidae Carcharhinus lim-
batus Blacktip shark DD 1 0,0
Batoid RHINOPRISTIFORMES Rhinobatidae Glaucostegus cemi-
culus Blackchin guitarfish EN 1 0,0
Shark HEXANCHIFORMES Hexanchidae Hexanchus nakamurai Bigeyed sixgill shark DD 1 0,0
Shark CARCHARHINIFORMES Carcharhinidae Rhizoprionodon
acutus Milk shark NE 1 0,0
Batoid MYLIOBATOFORMES Dasyatidae Taeniurops grabatus Round stingray DD 1 0,0
Total 4963
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recording of shark species occurrences. However, the
lack of both research programs and systematic sampling
protocols concerning Mediterranean and Black seas’
large elasmobranchs does not allow the reliable detection
of temporal and spatial trends, so far. In this sense, the
MEDLEM database is likely to provide an underestima-
tion of the real value of the incidental catches.
In terms of species composition, the only record-
ed species before 1890 were the basking shark and the
great white shark, with a sporadic presence of shortfin
mako in 1870-1890. In the last decades, many other spe-
cies were recorded (i.e., thresher shark, bluntnose six-
gill shark, devil ray, and shortfin mako), reaching a total
number of 34 species plus 2 categories of mixed species
(Fig. 1F). Unfortunately, information on the fishing gears
involved in the catches is often missing for most of the
recorded specimens. Almost 40% of total records (ap-
proximately 1000 individuals) is related directly to the
incidental catches that occur during normal fishing activ-
ities (Fig. 1C), mostly from trammel net, longlines and
Fig. 1: Number of the specimens recorded in the MEDLEM database by country (A). Proportional distribution of MEDLEM
records by species (B). Details on circumstances the species has been found or captured (C). Type of gear used to catch the fished
specimen recorded in the MEDLEM database (D). Others: rifle-harpoon 12; anchovy mid-water trawl 1; shrimp net 1; pole line
32. Number of registered records by year for each species (E). Number of records of the main species registered between 1990
and 2017 (F).
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282 Medit. Mar. Sci., 21/2 2020, 276-288
purse-seines. However, given that we know that during
these activities the majority of incidental catches are not
recorded, and occasional high catches sometimes occur
such as the Gaza Strip events described above, such spe-
cific episodes can cause high bias in the final analysis
(Fig. 1D).
The information’ spatial coverage is more complete
and more capillary in the Adriatic, Tyrrhenian, Aegean
and Balearic seas and the Strait of Sicily. The south-cen-
tral and south-western Mediterranean sectors provided
less information, probably as a result of lower coverage
of the collaborative research centres (Fig. 2). The great
white shark (C. carcharias) has been reported throughout
the Mediterranean with greater frequency in the north-
ern Adriatic Sea (FAO-GFCM’s Geographic Sub Area
[GSA] 17), Straits of Sicily (GSA 16) and Tyrrhenian
Sea (GSA9). It is also reported from Tunisian waters
(Bradaï & Saidi, 2013), Turkish waters and the Marmara
Sea (Kabasakal, 2003a; Kabasakal, 2008) (Fig. 3A). The
basking shark (C. maximus) has been reported in different
Mediterranean areas with some records distributed in all
GSAs. The majority of other records was observed (in
decreasing order) in the northern Tyrrhenian Sea (GSA 9)
(Serena et al., 1999b), Balearic Islands, northern coasts
of Spain (GSA 5 and 6), Adriatic Sea (GSA 17) (Man-
cusi et al., 2005), Tunisia (GSA 13 and 14) (Capapé et
al., 2003b), Turkey (Kabasakal, 2013b), Syria (Ali et
al., 2012) and northern Ionian Sea (Carlucci et al., 2014)
(Fig. 3B). Data suggest seasonal hotspots of basking
sharks around north Sardinia and Apulian coasts, where
individuals were recorded mainly between January and
March (De Sabata & Clò, 2010; Carlucci et al., 2014;
De Sabata et al., 2014. The shortfin mako (I. oxyrinchus)
has been recorded along the Italian coasts, mainly in the
northern Tyrrhenian and Adriatic seas, but also in Cre-
tan waters (GSA 23) and south Levantine waters (GSA
26) (Lteif, 2015); many records were reported also from
Tunisian waters (Bradaï et al., 2002). The largest short-
fin mako shark recorded in the Mediterranean Sea was
caught off south-western Turkey, and it was ca. 580 cm in
TL (Kabasakal & De Maddalena, 2011) (Fig. 3C).
The bluntnose six-gill shark (H. griseus) was reported
in Maltese waters (20 specimens; GSA 15), in the north-
ern Tyrrhenian Sea (45 specimens; GSA 9), in southern
Adriatic Sea, northern Ionian Sea, south Sicily waters
(21 specimens; GSA 18, 19 and 16 respectively), along
the coasts of Tunisia (GSA 13 and 14) (Capapé et al.,
2003a; Capapé et al., 2004) and in the Turkish waters (24
specimens). Kabasakal (2013b) states that 150 specimens
of H. griseus were caught by commercial fishing vessels
in the seas of Turkey between 16 July 1967 and 4 Feb-
ruary 2013, 90 of which were recorded in the Marmara
Sea (Fig. 3D). The bluntnose six-gill shark is also regu-
larly captured along the coast of Lebanon (Lteif, 2015.)
but currently not recorded in detail in the database. Also,
there are some incidental catches of H. griseus mainly
on deep bottom longlines as well as very rare inciden-
tal catches of A. vulpinus and A. superciliosus on surface
longlines targeting swordfish in the Aegean Sea and the
seas around Crete, but specific records could not be pro-
vided (Lanteri et al., 2017).
Even if its presence is known in many other areas, the
thresher shark (A. vulpinus) has been mainly reported in
the northern Tyrrhenian Sea (GSA9), Adriatic Sea (GSA
17) (Fortuna et al., 2010) and around Balearic Islands
(GSA 5). The thresher shark is also regularly observed
in the Gulf of Gabes (GSA 14) (Bradaï et al., 2002) but,
more recently, it seems to be more frequent along the
coasts of Tunisia (GSA 13) (Hattour & Nakamura, 2004)
(Fig. 3E).
The devil ray (M. mobular) was reported mainly in
the Tyrrhenian (GSA 9, 10 and 11) (Notarbartolo di Sci-
ara et al., 2015), Adriatic (Fortuna et al., 2014), northern
Ionian waters (GSA 17, 18 and 19), around Balearic Is-
lands (GSA 5), Tunisia coasts (GSA 13 and 14) (Bradaï
& Capapé, 2001) and in the Levantine basin (Gaza Strip,
see above; Fig. 3F) (Abudaya et al., 2017).
All spiny butterfly rays (Gymnura altavela) were re-
corded in the Balearic Islands (GSA 5) and the Levant
basin, along the Syrian coasts (GSA 27). In this last area,
114 specimens were collected by bottom trawlers and bot-
tom longlines from July 2010 to March 2013 (Alkusairy
et al., 2014). The species has also historically occurred
along Tunisian coasts, where individuals at all maturity
stages were observed (Capapé et al., 1992) but only one
occurrence was recorded in the Italian waters (Psomada-
kis et al., 2006) (Fig. 3G).
Some species, like the blue shark (P. glauca), are more
frequently caught as commercial bycatch, and thus reported
by various countries in the context of the European Union
Fig. 2: Spatial distribution of all MEDLEM records.
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Data Collection Framework (EU DCF). The blue shark
has been reported in both the western Ionian Sea (GSA 19)
and eastern Ionian Sea (GSA 20) - Crete (GSA 23), north
and south Levantine basin (GSA 24 and 26), Ligurian Sea
(GSA 9) (Serena & Silvestri, 2018), Tunisian coasts (GSA
13 and 14), and more frequently in the southern regions of
Tunisia (Bradaï et al., 2002) (Fig. 3H). However, such data
are not included in the MEDLEM database, since the by-
catch of this species is not considered as an unusual event.
Therefore, the map reporting the geographical distribution
of the blue shark is not representative of the actual distri-
bution of the species.
The MEDLEM data provided some insights on the
geographical distribution of other locally rare or uncom-
mon species, such as Lamna nasus (Fig. 3I), Carcharhi-
nus plumbeus, Galeorhinus galeus, and S. zygaena (Fig.
3J). A. superciliosus. I. oxyrinchus and G. altavela were
regularly present in Lebanese waters, whereas in the last
decade S. oculata and Sphyrna spp. seem to have com-
pletely disappeared in Lebanon, where M. mobular has
never been recorded (Lteif, 2015). The sandbar shark (C.
plumbeus) has been mostly recorded and landed through-
out the year in the Gulf of Gabes (Tunisia), and some
authors suggest that this area might be a nursery for many
Fig. 3: Spatial distribution of the principal species represented in the MEDLEM database. Carcharodon carcharias (A), Cetorhinus
maximus (B), Isurus oxyrinchus (C), Hexanchus griseus (D) Alopias vulpinus and bigeye thresher Alopias superciliosus (E), Mob-
ula mobular (F; in order to maintain a standard representation, the exceptional catches recorded in the Gaza strip are not shown),
Gymnura altavela (G), Prionace glauca (H), Lamna nasus (I) and, Sphyrna zygaena (J).
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284 Medit. Mar. Sci., 21/2 2020, 276-288
species (Bradaï et al., 2005; Saidi et al., 2005; Saidi et
al., 2007).
Whilst the two most recorded species, basking and
great white sharks, can be found all around the Medi-
terranean (whenever data is available), they probably
are not the most frequent species in this area. So far, the
geographical coverage of data sources and providers is
scattered and to obtain a sound indication on the “pres-
ence-absence” of the poorly represented species, the sci-
entific network and reporting system should be intensi-
fied, particularly in areas where the observation effort is
lower.
Finally, even though morphometric measurements are
scarce, some inferences can be drawn at least for some
species (Fig. 4A): for example, recorded specimens of
great white and basking sharks show a maximum total
length of 750 cm (with a minimum of 80 cm) for the
white shark and 1,000 cm for the basking shark (with a
minimum of 150 cm), respectively. For these two spe-
cies, information allowed the definition of length-weight
relationships which are shown in Figure 4 (B, C). In
both cases an exponential tendency is observed with an
acceptable model fitting, considering the low number of
records at disposal.
MEDLEM permitted not only to establish collabo-
rative interactions among many Mediterranean research
institutes but also to collect meaningful historical infor-
mation on the incidental captures of large and rare elas-
mobranchs in the last 350 years or so. This information
shows significant fluctuations in occurrences over time
and a prominent increase in the last ca. 30 years is likely
due to the increasing interest of the scientific community
on these species (Fig. 1E, 1F). Such an increase in record
frequencies was probably due to an increasing perception
of the importance of these species and their poor status
of conservation, as a consequence of the development of
specific studies and monitoring programs of marine re-
sources (Fig. 1F). On the other hand, the improvement of
fishing technologies and the consequent increase in fish-
ing effort may have played a role of primary importance,
determining a significant rise in incidental catches.
Some data from new scientific projects have recently
been added to the MEDLEM database (e.g., the catches
recorded with the Elasmoit Project (Relini et al., 2010)
and Elasmostat Project (Serena et al., 2014). A larger ef-
fort to retrieve all the historic information not yet avail-
able but included in governmental and scientific institu-
tions archives is needed. It is important to transfer into the
database the information on large elasmobranchs that was
collected through other monitoring activities such as EU
programmes (Reg. EC 1543/2000; Reg. EC 1639/2001;
Reg EC 812/2004; Reg. EC 1581/2004; Fortuna et al.
2010). It is also pivotal to create an international net-
work among the ongoing programs, such as SharkPulse
(www.sharkpulse.org) and the CIESM forum (Soldo et
al., 2014).
Because of its potential in collecting new information
throughout the Mediterranean basin and the involvement
of the various countries bordering the Mediterranean,
the MEDLEM archive is currently moving to the GFCM
server. This will enhance the collaboration among the
countries and researchers interested in the studies of car-
tilaginous fishes in the Mediterranean and Black seas. In
this sense, we have to take into account the GFCM Rec-
Fig. 4: Length frequency distribution of the main species recorded in the MEDLEM database (A). Length-weight relationship for
the great white shark (B) and the basking shark (C) in the Mediterranean Sea.
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ommendation 36/2012/3 and subsequent amendments
(Regulation 2015/2102 Art. 16j) on setting new fisheries
management measures for the conservation of sharks and
rays in the GFCM area. Its scope is to ensure high pro-
tection from fishing activities to elasmobranchs species
listed in Annex II of the SPA/BD protocol of the Bar-
celona Convention. Unfortunately, this Recommendation
is not always implemented in the Mediterranean coun-
tries, as shown by the frequent accidental catches by the
small-scale fisheries of I. oxyrinchus, C. maximus, etc.
and Squatina spp. specimens found in the bottom trawl-
ers’ catches (Serena & Silvestri, 2018). A special case is
the Palestinian fisheries in the Levantine basin targeting
the devil ray. This is probably a consequence of the 1993
Oslo Agreements, which imposed important restrictions
for Gaza fishers in terms of fishing area extent. These
restrictions have highly reduced the fishing opportuni-
ties for the Palestinian fleet and likely forced the local
fishermen to apply a subsistence fishing, less focused on
specific target species.
Greater attention to accidental catches occurring in the
various parts of the Mediterranean should be given and a
more systematic recording of these opportunistic events
should be facilitated. Several initiatives are taking place
in the Mediterranean Sea: integration and coordination
among them is pivotal (Bargnesi et al., 2020).This would
make the MEDLEM database a more comprehensive tool
that would not only enhance a pro-active collaboration
among the various research institutes, but also represents
an important source of information contributing to the
improvement of our knowledge on the biology of these
fishes, enabling the assessment of the status of the elas-
mobranchs and, lastly, the promotion of better conserva-
tion measures.
Acknowledgements
We would like to thank all our collaborators involved
in the MEDLEM project and to all the people who pro-
vided information from all around the Mediterranean and
Black seas. In particular, the Italian Coast Guard for help-
ing us to record the information collected during their in-
stitutional programs and the RAM (Reparto Ambientale
Marino) for sharing the archive of the official datasets.
Thanks to the anonymous referees for their critical read-
ing and valuable suggestions that allowed to obtain a
more exhaustive and precise text. Finally, thanks to Dan-
iela Pace (Sapienza University of Rome, Italy) for con-
stantly providing us with useful information on sharks at
sea.
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... As a bycatch species, the catch of blue sharks is intrinsically linked to abundance but also to global market demand, both being relatively complex drivers. Blue shark is amongst the most abundant shark species in international trade (Okes and Sant, 2019) for the meat and/or fins (e.g., dominant shark species for meat in Japan, Spain, Taiwan, and Uruguay: Okes and Sant, 2019;Brazil: Cruz et al., 2021;Italy: Serena and Silvestri, 2018;Mancusi et al., 2020). Overall, the importance of blue shark in the fin trade highlights its economic importance and the driver of the demand (Porcher et al., 2021). ...
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Blue shark (Prionace glauca) is amongst the most abundant shark species in international trade, however this highly migratory species has little effective management and the need for spatio-temporal strategies increases, possibly involving the most vulnerable stage or sex classes. We combined 265,595 blue shark observations (capture or satellite tag) with environmental data to present the first global-scale analysis of species’ habitat preferences for five size and sex classes (small juveniles, large juvenile males and females, adult males and females). We leveraged the understanding of blue shark biotic environmental associations to develop two indicators of foraging location: productivity fronts in mesotrophic areas and mesopelagic micronekton in oligotrophic environments. Temperature (at surface and mixed layer depth plus 100 m) and sea surface height anomaly were used to exclude unsuitable abiotic environments. To capture the horizontal and vertical extent of thermal habitat for the blue shark, we defined the temperature niche relative to both sea surface temperature (SST) and the temperature 100 m below the mixed layer depth (Tmld+100). We show that the lifetime foraging niche incorporates highly diverse biotic and abiotic conditions: the blue shark tends to shift from mesotrophic and temperate surface waters during juvenile stages to more oligotrophic and warm surface waters for adults. However, low productivity limits all classes of blue shark habitat in the tropical western North Atlantic, and both low productivity and warm temperatures limit habitat in most of the equatorial Indian Ocean (except for the adult males) and tropical eastern Pacific. Large females tend to have greater habitat overlap with small juveniles than large males, more defined by temperature than productivity preferences. In particular, large juvenile females tend to extend their range into higher latitudes than large males, likely due to greater tolerance to relatively cold waters. Large juvenile and adult females also seem to avoid areas with intermediate SST (~21.7-24.0°C), resulting in separation from large males mostly in the tropical and temperate latitudes in the cold and warm seasons, respectively. The habitat requirements of sensitive size- and sex-specific stages to blue shark population dynamics are essential in management to improve conservation of this near-threatened species.
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Collecting fine-scale occurrence data for marine species across large spatial scales is logistically challenging, but is important to determine species distributions and for conservation planning. Inaccurate descriptions of species ranges could result in designating protected areas with inappropriate locations or boundaries. Optimising sampling strategies therefore is a priority for scaling up survey approaches using tools such as environmental DNA (eDNA) to capture species distributions. eDNA can detect diverse taxa simultaneously, but to date has rarely been applied across large spatial scales relevant for conservation planning. In a marine context, commercial vessels, such as ferries, could provide sampling platforms allowing access to under-sampled areas and repeatable sampling over time to track community changes. However, sample collection from commercial vessels could be biased and may not represent biological and environmental variability. Here, we evaluate whether sampling along Mediterranean ferry routes can yield unbiased biodiversity survey outcomes, based on perfect knowledge from a stacked species distribution model (SSDM) of marine megafauna. Simulations were carried out representing different sampling strategies (random vs systematic), frames (ferry routes vs unconstrained) and number of sampling points. SSDMs were remade from different sampling simulations and compared to the perfect knowledge SSDM to quantify the bias associated with different sampling strategies. Ferry routes detected more species and were able to recover known patterns in species richness at smaller sample sizes better than unconstrained sampling points. However, to minimise potential bias, ferry routes should be chosen to cover the variability in species composition and its environmental predictors in the SSDMs. The workflow presented here can be used to design effective eDNA sampling strategies using commercial vessel routes globally. This approach has potential to provide a cost-effective method to access remote oceanic areas on a regular basis, and can recover meaningful data on spatiotemporal biodiversity patterns.
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The Mediterranean Sea is a hotspot for shark conservation. A decline in large pelagic shark populations has been observed in this vast region over the last 50 years and a lack of data on the local population status of various species has been pointed out. Throughout history, the relation between people and sharks has been revolving around a mixture of mystery, fear, and attraction. Recently, however, a remunerative ecotourism industry has been growing in areas of shark aggregation globally. This growth has been accompanied by the establishment of a citizen science (CS) movement aimed to engage and recruit ecotourists in data collection for shark research. Several CS projects have generated interesting results in terms of scientific findings and public engagement. In the Mediterranean Sea, shark aggregations are not as relevant to support locally-focused CS actions on shark diving sites as in other parts of the world. However, a series of other initiatives are taking place and CS could offer an excellent opportunity for shark conservation in the Mediterranean Sea. The dramatic decline of shark populations shown in the region calls for alternative ways to collect data on species distributions and abundance. Obtaining such data to set proper conservation and management plans for sharks in the Mediterranean Sea will be possible if existing CS initiatives collaborate and coordinate, and CS is widely acknowledged and deployed as a valuable tool for public education, engagement, and scientific discovery. After providing an overview of multiple facets of the relationship between humans and sharks, we focus on the possibility of exploiting new technologies and attitudes toward sharks among some groups of ocean users to boost participatory research. CS is a great opportunity for shark science, especially for areas such as the Mediterranean Sea and for large pelagic sharks whose populations are highly impacted.
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On 9th September 2015 the head of a shark belonging to the genus Alopias, was landed at Camogli harbour in the Ligurian Sea (North Western Mediterranean). The specimen has been caught 16 miles far from the coast (44° 06' N, 008° 57' E) as by-catch of the mesopelagic swordfish longline, but only the head was recovered, due to the predatory/scavenging activity by other shark specimens. The specimen was a female of big-eye thresher shark Alopias superciliosus a highly migratory species worldwide distributed in tropical and temperate waters but rarely caught in the Mediterranean Sea. The present record is the northenmost reported for this species in the Mediterranean area and the sixth in Italian waters
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Little is known about the giant devil ray (Mobula mobular), an endangered species endemic to the Mediterranean. Gaza is the only region where this species is targeted, hence, this fishery was studied to address the knowledge gap on fishery interactions, species behavior, and life-history traits. Devil rays have been frequenting this maritime area for at least the past 50 years for a short window from February to April. Landings are reported from 2005 to 2016, along with disc-width (DW) measurements for recent years. A total of 304 M. mobular (over 90% males) were landed in Gaza from 2014 to 2016, most which were mature and appeared to be mating (over 90% of males had sperm-filled claspers), providing critical insight that this area may serve as a mating ground. Yearly landings are shown here to closely match the allowed fishing distance from shore, which changes regularly, indicating that the rays are normally caught between 6 and 12 n.m. offshore. Width-weight conversion parameters are calculated for the first time for this species: a = 2.68 × 10⁻⁶ and b = 4.39. Fresh protein drives this local fishery, as food security is a major issue. An export market for gill plates was reported intermittently, and is no longer possible due to strict trade restrictions. We highlight the lack of awareness of fishers regarding the IUCN’s Red List ‘Endangered’ status of devil rays, and stress the urgent need for national protection of this species, particularly due to the species’ very slow life-history traits and probable usage of this area as a mating ground.
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Extremely low number of records off Turkish coast from 1950’s to date confirmed the rarity of Cetorhinus maximus in Turkish waters. A specific scientific monitoring program accompanied by zooplankton surveys should be implemented as soon as possible to figure out the seasonal movements of C. maximus in the mentioned region to answer the question whether the occurrence of basking sharks in Turkish waters exhibits a seasonality and site fidelity or not?
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One male and one female specimen of tiger shark, Galeocerdo cuvier (Péron & Lesueur, 1822), were accidentally caught by a drifting longline for swordfish in the south Mediterranean (Libyan waters). This finding confirms beyond any doubt that the tiger shark may be encountered in the waters of the Mediterranean Sea. Although records of this species has previously been reported, the information is partial or dubious, due to the lack of a description of the individuals found or the uncertain provenance of preserved material. Our finding confirms the record of this species in the southern part of the Mediterranean basin. Images, as well as morphometrics and information on stomach contents are given. Based on the size of the individuals, it is considered that the two specimens were born recently, presumably inside the Mediterranean Sea and likely close to the area where the individuals were found.
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This first issue of The State of Mediterranean and Black Sea Fisheries is a comprehensive review of the status and trends of fisheries in the Mediterranean and Black Sea. It includes eight chapters, separated in two parts: a first part on the status and trends of Mediterranean and Black Sea fisheries under different aspects such as fleet, catches, socio-economic variables, bycatch, small-scale fisheries and stock status, and a second part describing management measures adopted by the GFCM towar ds the sustainability of fisheries in its area of application. The report is based to a large extent on the most up-to-date data available submitted by GFCM contracting and cooperating non-contracting parties, including information on stock status, national catches, fleet and socio-economic information up to 2014. It is also complemented with information from other sources, including literature review and, for small-scale fisheries, the outcomes of the First Regional Symposium on Sustainable Small-Scale Fisheries in the Mediterranean and Black Sea, organized in 2013 in Malta.
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Sharks and rays are threatened by overfishing, yet we have little idea of the conservation status of the hundreds of Data Deficient species. Here, we developed an ecological trait model to predict the categorical conservation status of 22 Northeast Atlantic and 13 Mediterranean Sea Data Deficient sharks and rays. We first developed an explanatory cumulative link mixed model based on regionally data-sufficient species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species™ using maximum body size, median depth, and reproductive mode, then predicted the statuses of Data Deficient species. Species exclusive to the Mediterranean were 3.8 times more likely to be threatened than species exclusive to the Northeast Atlantic. Over half of Northeast Atlantic (55%, n = 12 of 22), and two-thirds of Mediterranean (62%, n = 8 of 13) Data Deficient species were predicted to be threatened. When applied to all data-sufficient species, the mean predictive accuracy was 71% and 66% for the Northeast Atlantic and Mediterranean models, respectively. Overall, Northeast Atlantic Data Deficient species are predicted to be 1.4 times more threatened than data-sufficient species proportionally (39% assessed-threatened, n = 38 of 98), whereas threat levels in the Mediterranean Sea are similarly high for both (65% assessed-threatened, n = 39 of 60 data-sufficient). With the growing availability of vertebrate trait databases, trait-based, categorical prediction of conservation status is a cost-effective approach towards incorporating Data Deficient species into unbiased (i) estimates of lineage-wide extinction rates, (ii) protected species lists, and (iii) Red List Indices, thus preventing poorly-known species from reaching extinction unnoticed.
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One hundred and fifty specimens of Hexanchus griseus (Bonnaterre, 1788) were caught by commercial fishing vessels in the seas of Turkey, between 16 July 1967 and 4 February 2013. Regarding the number of captured specimens per marine areas, the highest number of captures was recorded in the Sea of Marmara (90 specimens; 60%), followed by the Aegean (41 specimens; 27.3%), Mediterranean (15 specimens; 10%) and Black (3 specimens; 2%) seas. A single stranded individual was also recorded in the Çanakkale Strait. Regarding the number of recorded specimens it is obvious that the Sixgill Shark Data Bank of Turkey holds a significant number of H. griseus specimens caught in the eastern Mediterranean Sea, both reported in historical and contemporary studies. The sex ratio of the examined specimens of H. griseus is 1:2.61 in favour of females. Analysis of the fishing gear used for 72 of 150 examined sixgill sharks indicates that the most common fishing gear used to catch H. griseus is purse-seine, followed by several types of bottom fishing gear. Total length of the recorded specimens ranged between 50 and > 650 cm TL for both sexes; however, catches were dominated by two size groups, 250-350 cm and 350-450 cm TL, respectively.