|Scientific Name:||Leucoraja melitensis|
|Species Authority:||(Clark, 1926)|
|Taxonomic Notes:||The subgenus Leucoraja was elevated to genus rank by McEachran and Dunn (1998).|
|Red List Category & Criteria:||Critically Endangered A2bcd+3bcd ver 3.1|
|Assessor(s):||Dulvy, N. & Walls, R.|
|Reviewer(s):||Mancusi, C. & Kemp, J.R.|
|Contributor(s):||Ungaro, N., Serena, F., Tinti, F., Bertozzi, M., Pasolini, P., Mancusi, C. & Notarbartolo di Sciara, G.|
Maltese Skate (Leucoraja melitensis) is a demersal species that is endemic to the Mediterranean Sea. Historically, this species was moderately common off Tunisia and Malta, and rare off France, Algeria and Italy. It now appears to be mostly restricted to one small part of the Mediterranean Sea, the Sicilian channel around Malta Island, which is subject to heavy trawling activity. In the 1990s, surveys no longer detected this skate in the Gulf of Lion. It was extremely rare in the western central Mediterranean Sea (the coasts of Tyrrhenia, Corsica, Sardinia and Sicily) according to the International Trawl Surveys in the Mediterranean from 1994 to 1999 (i.e., recorded in 20 of 6,336 hauls). It is now more rare off Malta and rare or absent off Tunisia. Maltese Skate is assessed as Critically Endangered under criteria A2bcd+3bcd as a result of a suspected population size reduction of at least 80% over a three generation period (15 years), based upon its endemism to the region, inferred reduction in the area of occupancy, and inferred population reductions off the Maltese, Tunisian and French coasts. The population is also suspected to continue declining around 80% in the future over the period of three generations. More research is needed on its range, biology, ecology, exploitation, and abundance.
|Range Description:||The species is endemic to the Mediterranean. Its range now appears to be restricted to the Sicilian Channel around Malta (GFCM 2012). The depth range is 60−800 m, but it is most commonly found between 400−800 m.|
Native:Algeria; Italy (Sicilia); Libya; Malta; Tunisia
|FAO Marine Fishing Areas:||
Mediterranean and Black Sea
|Range Map:||Click here to open the map viewer and explore range.|
This is one of only four skate species endemic to the Mediterranean Sea, and has undergone significant declines and a reduction in its geographical range. Historically, its range once extended over about one quarter of the total area of the Mediterranean Sea (at least within the depth range of the main trawl fisheries). It was moderately common off Tunisia, common around Malta, rare off Algeria and recorded once off Italy (Stehmann and Bürkel 1984). The range of this skate now appears to be restricted to the Sicilian Channel (Pipitone et al. 1992, Relini 1995, Cannavò et al. 1999), and it is considered rare off Malta (Schembri et al. 2003) and rare or absent off Tunisia (Bradaï 2000). In Italian waters, trawl surveys performed by Gruppo Nazionale risorse Demersali (GRUND) between 1985 and 2000 only recorded this species in the Sicilian Channel (20 of 23 hauls in this area; Relini et al. 2000, Ragonese et al. 2003).
In surveys conducted in the northern Mediterranean Sea from the Alboran to Aegean Sea (including off Sicily), the International Trawl Survey in the Mediterranean (MEDITS) recorded this species in only 20 out of 6,336 hauls between 1994 and 1999 (Bertrand et al. 2000, Baino et al. 2001). In this area, the standing stock biomass of this species was estimated to be 705 tonnes. If the average weight of an individual is ~2 kg, the estimated population size in the MEDITS survey area was ~35,200 individuals at this time (note that this does not include any remaining population around Malta and North Africa).
Records from surveys of the Gulf of Lion infer that this species was present on the continental shelf in 1957−1960 and slope in 1980−1984, but not in comparable surveys carried out in 1992−1995 (Aldebert 1997). However, caution should be taken with these findings because the species could be confused with Cuckoo Skate (Leucoraja naevus), which is widespread in the western part of the Mediterranean Sea.
In a recent study, bottom trawl hauls of commercial vessels operating in the Aegean Sea were analysed three times per year from 1995 to 2000 and 2003 to 2006 (Damalas and Vassilopoulou 2011). A mean nominal catch per unit effort declined by 50% in the number of individuals (from 0.22 to 0.11 individuals per haul) and by 60% in weight (from 0.05 to 0.02 kilograms per haul) between the two time frames. The last encounter with this species in the Adriatic Sea was a single individual recorded during bottom trawl surveys in 2005 (Ferretti et al. 2013).
A decline of at least 80% of the population is suspected in European waters based on the fact that it has disappeared from over 80% of its former range over a 15 year period.
|Habitat and Ecology:||
This benthic skate occurs over sandy and sandy-muddy bottoms at depths of 60−800 m, but most commonly 400−800 m.
Little is known about the reproductive cycle of this skate. Breeding occurs throughout the year, though ovulating females have mainly been observed in the spring and autumn (Stehmann and Bürkel 1984, Serena 2005). Females produce 10−56 eggs per year (Bauchot 1987). Both males and females mature at ~40 cm total length (TL; Bauchot 1987, Notarbartolo and Bianchi 1998), and the maximum reported size is ~50 cm TL (Stehmann and Bürkel 1984). In Italian waters, the size range of this species was reported to be 9−42 cm TL between 1985 and 2001 (Ragonese et al. 2003). Its generation length is suspected to be 4-5 years.
|Use and Trade:||The species is not exploited nor traded commercially.|
The majority of this species’ geographic (i.e., in the Sicilian Strait around Malta) and depth (400−800 m) range occurs where trawling activity is intensive. The Sicilian Channel is the most exploited region of the Italian coast with respect to the total number of fishing vessels of any kind compared to other parts of the basin. Most of the fleet is composed of multipurpose artisanal vessels using bottom longlines, gillnets and trammel nets, all gear types that are likely to catch this species. Trawl fishing vessels constitute 11% of the fleet (Relini et al. 2000). While this skate is not known to be targeted by commercial fisheries, it is taken as bycatch in bottom trawl, gillnet, and bottom longline fisheries and often discarded (Ragonese et al. 2003). Skates generally have low commercial value in the Mediterranean region, but occasionally this species is present in fish markets. Usually only the large individuals are landed for human consumption, however, there is full retention of all size classes in the cod-end of gears currently used, regardless of mesh size (Ragonese et al. 2001).
Along the Tunisian coast, this species is occasionally caught as bycatch in bottom trawl, gillnet, and bottom longline fisheries, but it is now extremely rare in this area (Bauchot 1987). Maltese fisheries using bottom longline and trawl gear may take this species as bycatch (De Leiva et al. 1998), although Maltese fishing fleets are smaller to those of the Italians’. Tunisian fisheries are small, coastal and probably operate outside this species’ area of occurrence (Samira 2002).
Benthic trawling effort over the continental shelf and slope in the Mediterranean Sea increased with respect to fishing effort and technological advances over a period of 60 years, although it is unclear if fishing effort will continue to increase within this species range. Fishing effort and catches should be monitored closely.
According to the Fisheries and Aquaculture Organisation’s (FAO) International Plan of Action on the management and conservation of sharks (IPOA-Sharks), all states that capture sharks, rays, skates or chimaeras, either as target species or as bycatch, shall implement national action plans to ensure suitable use, conservation and recovery of threatened species (Vacchi and Notarbartolo 2000).
In 2012, parties to the Barcelona Convention agreed that this species (as listed in Annex II of the Specially Protected Areas and Biological Diversity (SPA/BD) Protocol for the Mediterranean Sea) cannot be retained on board, transshipped, landed, transferred, stored, sold, displayed or offered for sale, and must be released unharmed and alive, to the extent possible, in the Mediterranean Sea (FAO 2012). Furthermore, the Italian National Action Plan was drafted by the Central Institute for Marine Research (ICRAM) scientific advisory committee to provide Italy with tools needed to ratify the SPA/BD Protocol (Serena et al. 2002, Vacchi and Notarbartolo 2000). The European Commission also drafted a proposal for the European Community Plan of Action that encourages research programs aimed at the assessment of the conservation status of cartilaginous fishes in the Mediterranean Sea (Serena et al. 2002).
Italy should act urgently to establish a plan of action for the conservation and management of chondrichthyans. To mitigate the decline of this species caused by fisheries bycatch, it is recommended that opportunities to ban trawling in specific areas of the Mediterranean Sea be explored. Mesh size restrictions are unlikely to be effective given that full retention in the cod-end of trawling gear is expected for mesh sizes ranging from 16 to >60 mm (Ragonese et al. 2001). The most appropriate management measure may be to define areas of suitable habitat for this species that are also unsuitable for bottom trawling and close them to trawl fisheries in order to protect part of the population and the eggs from exploitation (Ragonese et al. 2003).
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|Citation:||Dulvy, N. & Walls, R. 2015. Leucoraja melitensis. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 06 July 2015.|