ISRA FACTSHEETS
ISRA FACTSHEETS
MEDITERRANEAN AND BLACK SEAS REGION
Strait of Sicily and Tunisian Plateau
Summary
Strait of Sicily and Tunisian Plateau is located between Sicily, Malta, western Libya, and Tunisia, encompassing Pantelleria Island, Kerkennah Islands, and the Egadi and the Pelagie Archipelagos. The area is characterised by diverse habitat features, such as submerged volcanic seeps, trenches, canyons, seamounts, banks, and sensitive habitats (e.g., cold-water corals and seagrass beds). The area overlaps with the Sicilian Channel Ecologically or Biologically Significant Marine Area. Within this area there are: threatened species (e.g., Common Guitarfish Rhinobatos rhinobatos); range restricted species (e.g., Rough Skate Raja radula); reproductive areas (e.g., White Shark Carcharodon carcharias); undefined aggregations (e.g., Sandbar Shark Carcharhinus plumbeus); and the area sustains a high diversity of sharks (32 species).
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Strait of Sicily and Tunisian Plateau
DESCRIPTION OF HABITAT
Strait of Sicily and Tunisian Plateau is located between Sicily, Malta, Tunisia, and Western Libya, encompassing Pantelleria Island, Kerkennah Islands, and the Egadi and the Pelagie Archipelagos. The area delimits the border between the western and eastern Mediterranean sub-basins and includes part of the Sicilian and Tunisian shelves. It is considered topographically complex resulting in highly diverse habitats. It is characterised by an extended continental shelf on the southern part of Sicily, several trenches in the central part of the area, seamounts (e.g., Aceste, Tiberio, and Scuso) and banks (e.g., Skerki and Marettimo) in its northwestern side, and the Malta Bank in the eastern part. Emerging volcanic Islands include Linosa and Pantelleria Island and 12 submerged volcanoes (Civile et al. 2016). The seafloor is characterised by high heterogeneity of benthic communities, including sensitive habitats (e.g., deep cold-water corals, maërl habitats, and shallow seagrass meadows), and shallow areas covered by sandy beds (Calcinai et al. 2013). The slope is irregular, characterised by steep trenches, troughs, and escarpments.
The Atlantic Ionian Stream flows eastward through the area and is the main driver of surface circulation, promoting the formation of two large cyclonic vortices on the Adventure and Malta Banks. The Atlantic Ionian Stream also promotes the formation of coastal upwellings as it interacts with complex bottom topographies, which, together with the mesoscale vortices, support high levels of primary and secondary production. The Levantine Intermediate Water is a westward flowing water mass in the intermediate layers (200–400 m).
The area overlaps with the Sicilian Channel Ecologically or Biologically Significant Marine Area (EBSA; CBD 2023).
This Important Shark and Ray Area is benthopelagic and is delineated from inshore and surface waters (0 m) to 2,000 m based on the depth range of the Qualifying Species.
CRITERION A
VULNERABILITY
Thirty-two Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened SpeciesTM regularly occur in the area. Threatened sharks comprise five Critically Endangered species, five Endangered species, and eight Vulnerable species; threatened rays comprise five Critically Endangered species, five Endangered species, and three Vulnerable species; and threatened chimaeras comprise one Vulnerable species (IUCN 2023).
CRITERION B
RANGE RESTRICTED
This area holds the regular presence of two resident range-restricted species. Maltese Skate and Rough Skate are regularly encountered and caught in the area by fisheries that operate locally (Kadri et al. 2014a; Lauria et al. 2015; Tiralongo et al. 2018; Follesa et al. 2019; Geraci et al. 2021; Di Lorenzo et al. 2022; Falsone et al. 2022; Saidi et al. 2023; C Cattano unpubl. data 2023). The area is considered more important for Rough Skate than other areas in the Mediterranean Sea. The Maltese Skate and Rough Skate occur only in the Mediterranean Sea Large Marine Ecosystem.
CRITERION C
SUB-CRITERION C1 – REPRODUCTIVE AREAS
Strait of Sicily and Tunisian Plateau is an important reproductive area for four shark and three ray species.
Fishery-dependent, local ecological knowledge (LEK), and Baited Remote Underwater Video Surveys (BRUVS) data show that the Gulf of Gabès in Tunisia and the Pelagie Islands in Italy are among the most important space-use spots for various lifecycle stages of Sandbar Shark (Echwikhi et al. 2013; Enajjar et al. 2015; Saidi et al. 2019; 2020; 2023; Cattano et al. 2021; 2023). Known parturition sites for Sandbar Shark are reported in the Gulf of Gabès (Enajjar et al. 2015). Parturition occurs in the boreal summer (June–July), with young-of-the-year (YOY) remaining in the area year-round (Enajjar et al. 2015; Saidi et al. 2019; 2020; 2023). Fishery-dependent data show that Sandbar Shark neonates (<70 cm TL) incidentally caught by the grouper longline fishery in the Gulf of Gabès, represented between 6–10% of individuals (n = 140) over two consecutive fishing periods in 2016 and 2017 (Saidi et al. 2023).
The area has been historically considered a reproductive area for White Sharks (Fergusson 1996). Despite significant population declines, one the highest reported occurrence of young-of-the-year individuals (n = 14) from the Mediterranean Sea has been recorded in the area, especially from May to August (Boldrocchi et al. 2017). Pregnant females or young-of-the-year have been reported on the continental shelf waters of Sicily, Tunisia, and Libya (e.g., Saïdi et al. 2005; ICSEM 2013; Boldrocchi et al. 2017; Jambura et al. 2021). The number of reliable capture reports between 2000 and 2012 is 34 (n = 59 from 1953 to 2012). Neonates are caught mainly in trawls (ICSEM 2013).
Local ecological knowledge, pelagic BRUVS, and fishery-dependent surveys suggest that young-of-the-year Shortfin Mako are recurrently encountered or caught on longlines around banks, shoals, and slope zones in the southeastern part of the area, off the Pelagie Islands and off the Tunisian coast (Saidi et al. 2023; C Cattano & M Milazzo unpubl. data 2023). Sizes captured or documented on BRUVS in July and August are between 71–81 cm TL (average of 3.1 young-of-the-year for every 1,000 hooks) which is within the reported global size-at-birth for the species (Stevens 1983; University of Palermo 2023). These data suggest the area provides advantage to the young and supports them at various lifecycle stages.
Pregnant Common Smoothhounds are recurrently caught from February to April both in the northern and the southern sectors of the Strait of Sicily and Tunisian Plateau according to scientific trawl surveys, monitoring of fishery landings, and LEK (Enajjar et al. 2015; Colloca et al. 2020; Di Lorenzo et al. 2022; Saidi et al. 2023). In addition, studies conducted in the Gulf of Gabès over a four-year period documented neonates with open umbilical scars which represented 12% of animals landed from April to July (Enajjar et al. 2015).
Neonate Blackchin Guitarfish (<38 cm TL, n = 95) and Common Guitarfish (<29 cm TL, n = 40) are regularly caught in the shallow waters of the Gulf of Gabès by trawl and trammel nets in late summer and early autumn (Enajjar et al. 2015). Evidence of neonates of these species is only available for this specific location, highlighting the importance of this area for the early life stage of these species.
A seasonal reproductive area for the Common Eagle Ray has been identified in the Egadi islands (Grancagnolo & Arculeo 2021; University of Palermo 2023). Public videos uploaded on social media platforms in September 2019, 2020, and 2021, as well as field studies using underwater visual censuses, diver operated video systems, fixed video cameras, and BRUVS conducted in the summers of 2020, 2021, and 2022 recorded up to 93 individuals aggregating and five pregnant females (University of Palermo 2023). Courtship (n = 78) and mating (n = 99) events were also recorded mostly during the first daylight hours (University of Palermo 2023).
CRITERION C
SUB-CRITERION C5 – UNDEFINED AGGREGATIONS
This area hosts undefined aggregations of the Sandbar Shark. Adults and sub-adults aggregate from mid-July to October in the Pelagie Archipelago (Italy). Aggregations have been documented since the late 1950s around Lampione Island and monitored continuously by BRUV and diver operated video systems from 2019 onwards (Merlo 1964; Cattano et al. 2021, 2023; SZN 2023). Data from BRUVS recorded up to five individuals in a single frame in 2019, at a depth of 20–40 m (Cattano et al. 2021). Divers’ videos have documented aggregations of up to 18 individuals using an area at the same time (SZN 2023). Further information is required to understand the function of these aggregations.
CRITERION D
SUB-CRITERION D2 – DIVERSITY
The area sustains a high diversity of Qualifying Species (32 species). This exceeds the regional diversity threshold (19 species) for the Mediterranean and Black Seas region. The regular presence of Qualifying Species has been documented through scientific benthic trawl surveys within the Mediterranean International Trawl Survey (MEDITS) and the Italian National Survey Program (GRUND) projects and other published studies (Ragonese et al. 2013; Zava et al. 2016; Boldrocchi et al. 2017; Giovos et al. 2019; Saidi et al. 2019; 2020; 2023; Cattano et al. 2021; Geraci et al. 2021; La Mesa et al. 2021; Di Lorenzo et al. 2022; Falsone et al. 2022), technical reports (University of Palermo 2023), and unpublished data sources (e.g., C Cattano unpubl. data 2023; G Notarbartolo di Sciara unpubl. data 2023).
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