Checklist of the sixteen
In the present work, an overview of the demersal (sharks‐chimaera) and bottom dwelling (batoids) of experimental survey international bottom trawl survey in the mediterranean (MEDITS) data, from 1994 to 2013, is provided. The analysed data refer to a wide area located off the southern coast of Sicily, namely south of Sicily (according to the general fisheries commission for the mediterranean (GFCM) classification, Geographical Sub‐Area 16). A checklist of the recorded Chondrichthyes was integrated by density index, D.I. (N/Km2) and average individual weight (as the ratio between biomass index, D.I. (N/Km2) and D.I.). Results suggest that most of the Chondrichthyes in South of Sicily are in a steady state, although in the last few years, they seemed to recover. The spatial distribution of sharks‐chimaera in the geographical sub‐area (GSA) 16 is mainly concentrated in the southern and north‐western zones. Nevertheless, possible management actions to promote the recovering of these very important ecological and threatened species are discussed.
- South of Sicily
- Mediterranean Sea
Marine cartilaginous species present unique challenges for conservation assessment (in Refs. [1, 2]). They are considered the most vulnerable species to fishing activity. Groundfish sharks and chimaera, together with bottom dwelling batoids, share several biological traits, for example: high position in the trophic food webs, slow growth, delayed sexual maturity, low fertility and long life spans. Generally, they form small local stock (the so‐called stock‐let) with limited or low connectivity to each other (in Refs. [3–5]). The assumption that marine fish are not vulnerable to extinction because they live in open seas where their movements are unlimited is unfounded. Fisheries have caused severe declines in many species, and although there are still no documented cases of complete extinction, there is considerable debate as to whether marine species could become extinct (in Refs. [2, 6, 7]).
In many areas of the world, a generalised decline of cartilaginous fish species standing stocks is generally recognized mainly because of fishing effort increase; the apparent paradox of a corresponding increase in landings of some stock likely reflects the reduction of the discarded catch due to the general crisis of the sector. Overfishing, habitat degradation and slow recovery rates are potential factors that lead to such dramatic declines, especially in areas such as the Mediterranean Sea where fishing (both legal and illegal) has long been a way of life and continues to be intense. As a matter of fact,
In this context, current Mediterranean elasmobranchs are represented by ∼85 shark and batoid species (in Ref. ) more or less in an over‐exploited condition (i.e. standing stock very reduced); in particular, 31 species (40%) are regionally classified as threatened categories (critically endangered, endangered or vulnerable) (in Ref. ). The Mediterranean catches are multi‐species with a rich marine community, including selachians, historically exploited by different fisheries (in Ref. ). In the wide area between the Southern Sicily and the Northern Coasts of Africa,
Secondly, in the past poor data were recorded on these
Thirdly, the scarce selectivity of the commercial trawling cod‐end (diamond, 20–30 mm side stretched; in Ref. ) together with the 5–6 hours for haul, has determined a huge catch of
To improve the knowledge on
2. Overview of the
The used data were gathered during MEDITS survey program and specifically referring to the South of Sicily (geographical sub‐area (GSA) 16 according to GFCM classification). This area extends for about 34,000 km2 and is characterized by the entry of the modified Atlantic Water (AW), which flows towards east in proximity of the surface (up to around 200 m), and from the spillage of warmer and salty water (200–500 m), the levantine intermediate water (LIW), which flows towards west, along the Sicilian slope (Figure 1).
In the investigated area, bottom trawling is forbidden (but such a measure is rarely enforced within 50 m of depth) from the Sicilian coasts and in some specific grounds (such as the Egadi Islands marine protected area, MPA). The data referring to the MEDITS Survey from 1994 to 2013 were carried out with a commercial stern trawler harboured in Mazara del Vallo, the Sant’Anna (32.2 m length overall; powered with a 736 kW engine). The sampling stations have been distributed applying a stratified sampling scheme with random drawing inside the following bathy‐metric limits: 10–50 m (a
In the present study, a checklist of
In the South of Sicily, overall 37 species were recognized as captured at least once: 16 demersal sharks‐chimaera and 21 batoids. In particular, four sharks‐chimaera orders (
2.1. Blackmouth catshark
— G. melastomusRafinesque, 1810
This small‐sized shark lives in deep waters from 150 to more than 2000 m (in Ref. ), even though it can be occasionally (especially juveniles) found over the inner shelf (50–60 m) (in Refs. [25, 26]). In the Mediterranean, it reaches a maximum size of 63 cm total lenght (TL) (in Refs. ).
2.2. Small‐spotted catshark—
Scyliorhinus caniculaLinnaeus, 1758
A bottom dweller shark measuring up to 90–100 cm of TL (in Refs. [30, 31]) lives in gravel, sandy and muddy bottoms down to 800–1000 m, but preferably within the 400–500 m depth range (in Refs. [32, 33]). The Small‐spotted catshark is an opportunistic predator on a wide range of macrobenthic fauna (generalist feeder). In particular, natantian and reptantian crustaceans together with teleosts were the most important preys (in Ref. ).
Scyliorhinus stellarisLinnaeus, 1758
Its habits are similar to the Small‐spotted catshark, but it prefers the rocky zones from 20 to 100 m (in Refs. [30, 31]), although it is even able to go down to 800 m (in Ref. ). In the Mediterranean, its maximum size is 150 cm TL (in Ref. ). The Nursehound feeds on benthic prey, mainly on crustaceans, molluscs, some bony fishes and on its congeneric small spotted catshark,
2.4. Starry smooth‐hound—
Mustelus asteriasCloquet, 1821
A slender shark measuring up to 140 cm TL (in Ref. ), though occurring below, from a few metres to about 100 m (in Ref. ), can be caught below 300 m (in Ref. ) and sometimes deeper at 500 m (in Ref. ). Starry Smooth‐hound feeds predominantly on crustaceans, including squat lobsters and crabs, and especially swimming crabs. Predation on other taxa is low (in Ref. ). In the Mediterranean Sea, trawling and artisanal fishing have largely exploited the
Mustelus mustelusLinnaeus, 1758
This species measures up to 160 cm TL (in Ref. ) and lives at 800 m depth (in Ref. ), but shows a preference for shallow sandy‐muddy bottoms, especially at 5–50 m depth (in Refs. [30, 31]. Gracan et al. (in Ref. ) declared that
2.6. Blackspotted smooth‐hound—
Mustelus punctulatusRisso, 1827
As the similar species of
Chimaera monstrosaLinnaeus, 1758
This Atlanto‐Mediterranean deep‐water animal prefers cold waters and occurs in all the Mediterranean, except the North Adriatic (in Ref. ). Its depth limits range from the outer shelf down to ca. 1600 m (in Ref. ). Maximum length is 150 cm TL and maximum age is 26 and 30 years for females and males, respectively (in Ref. ).
2.8. Sharpnose sevengill shark—
Heptranchias perloBonnaterre, 1788
This shark is easily recognizable for the presence of seven gill slits and occurs in the whole Mediterranean showing a wide depth‐distribution from 0 to 50 m down to 800 to 1000 m (in Refs. [8, 31]). The newborn is ca. 30 cm TL and during adulthood reaches 90–100 cm TL, attains a maximum size of up to 140 cm TL (in Ref. ) and feeds on small sharks and rays, small bony fish, shrimps, crabs, lobsters, squid and cuttlefish (in Ref. ). It is taken by a wide variety of demersal fisheries and sold at the supermarket.
2.9. Bluntnose sixgill shark—
Hexanchus griseusBonnaterre, 1788
Bluntnose sixgill shark lives up to 2500 m depth (in Ref. ) although during the night it was noticed at a depth around 30–40 m in the Straits of Messina (in Ref. ). The maximum TL recorded was 600 cm (in Ref. ). This shark is taken as bycatch in handlines, longlines, gillnets, traps, trammel nets, and both mid‐water and bottom trawls. There are some small‐scale fisheries for this species in the Mediterranean (in Ref. ). In the mid 80s, large sized animals were commonly found at the fish market in Mazara (Sicily) and sold as slices of ‘Palumbo’ (the Sicilian name for
2.10. Gulper shark—
Centrophorus granulosusBloch and Schneider, 1801
A common deep‐water species (often confused with the congener
2.11. Little Gulper shark—
Centrophorus uyatoLinnaeus, 1758
Demersal on the continental shelf and upper‐middle continental slope at depths of 50 to 1,400 m, This invalid
2.12. Kitefin shark—
Dalatias lichaBonnaterre, 1788
A benthic to mesopelagic deep‐water shark occurring at depths between 90 and 1400 m (in Ref. ), which grows up to 180 cm TL (in Ref. ); however, 120 cm is a more common length (in Ref. ). Navarro et al. (in Ref. ) revealed a preference for small sharks; however, finfish, crustaceans and cephalopods were also found. The species occurs within the range of fisheries in many areas of its range, where it is taken as bycatch. It is sometimes sold at the fish markets, but normally it is discarded (especially by Sicilian red shrimp trawlers) (in Ref. ).
2.13. Velvet belly—
Etmopterus spinaxLinnaeus, 1758
This Atlanto‐Mediterranean deep‐water shark has a benthic life on the shelf and bathyal zones, from 70 to about 2500 m (in Ref. ) but mostly below 200 m depth (in Ref. ).
2.14. Angular roughshark—
Oxynotus centrinaLinnaeus, 1758
Angular roughshark lives in a bathymetric range from 60 to 660 m (in Ref. ); however, it can reach a depth up to 800 m (in Ref. ). The maximum TL recorded was 150 cm (in Ref. ). The reported diet of this species is mainly characterized by small crustaceans (in Ref. ), polychaetes (in Ref. ) and teleosts (in Ref. ). Guallart et al. (in Ref. ) considered
2.15. Piked dogfish—
Squalus acanthiasLinnaeus, 1758
Piked dogfish is a small bottom‐dwelling shark with a maximum recorded size of 160 cm TL and maximum weight of 91 kg (in Ref. ) with a maximum depth of 800 m (in Ref. ). It can be considered an opportunistic feeder. Their natural diet composed mainly of teleost fishes, followed by crustaceans, nematodes and actinarians (= sea anemones) (in Ref. ). It’s taken as bycatch in demersal fisheries and sold at supermarket (in Ref. ).
2.16. Longnose spurdog—
Squalus blainvilleRisso, 1827
It is a small shark measuring up to 110 cm TL and occurring at 700 m depth (in Ref. ). In the stomach, contents of
2.17. Common stingray—
Dasyatis pastinacaLinnaeus, 1758
It occurs from the shore to about 200 m depth, but is more commonly found in shallow waters <50 m (in Refs. [12, 64, 65]). It feeds on a wide variety of bottom‐dwelling organisms. In a study by Ismen , crustaceans represented more than 99% of the diet when pooling all size classes, but teleost fish were of increasing importance in the diet of larger stingrays. The common stingray has been reported to reach a disc width (DW) of 1.4 m and a TL of 2.5 m, though a DW of 45 cm is more typical. Common stingrays are caught incidentally by commercial fisheries across many parts of its range, using bottom trawls, gillnets, bottom longlines, beach seines, and trammel nets (in Ref. ).
It is discarded after fishermen cut off the dangerous tails (in Ref. ), which have caused at least one fatality among fishers from Mazara.
2.18. Blue stingray—
Pteroplatytrygon violaceaBonaparte, 1832
It occurs from over the edge of continental and insular shelves into the open water but has been reported at 238 m depth. In the Adriatic water, the diet consisted of two main taxonomic groups such as teleost fish and cephalopods, but few specimens of crustaceans were also recorded (in Ref. ). This species is captured by pelagic longline fisheries operating in the Mediterranean Sea (in Ref. ).
2.19. Common eagle ray—
Myliobatis aquilaLinnaeus, 1758
The common eagle ray in the Mediterranean is reported on sandy and muddy substrates, from shallow water to 200 m depth, although it was reported at the depth of 537 m off southern African coast (in Ref. ). It is a relatively small ray, attaining a maximum size of 80 cm DW (in Ref. ). It feeds on invertebrates such as crabs, mole crabs and bivalves, and on small bony fishes. The wings are said to be good eating and along the African coast are regularly used for human consumption. The species represent a regular bycatch in mixed species fisheries (in Ref. ).
2.20. Bull ray—
Pteromylaeus bovinusGeoffroy St. Hilaire, 1817
It has a moderate depth range from costal water to about 30 m, occasionally in oceanic water up to100 m of depth. In Eastern Mediterranean Sea, Dulcic et al. (in Ref. ) found a max TL of 2940 cm and 220 cm DW for female. Regarding feeding aspects, it is known that they prey on bottom‐living invertebrates such as crustaceans (crabs, prawn) and mollusks (squids, bivalve) (in Ref. ). Bull rays are very rare and not commonly caught by fisherman; they are mainly discarded at sea (in Ref. ).
2.21. Gray skate—
Dipturus batisLinneo, 1758
Gray skate is found from shallow coastal waters to depths of 600 m, but most commonly found at 200 m depth. Maximum‐recorded TL is 250 cm (in Ref. ).
2.22. Longnosed skate—
Dipturus oxyrinchusLinneo, 1758
Longnosed skate is found in water from 90 to 900 m, commonly around 200 m (in Ref. ). In the Mediterranean Sea, typical TL varies between 60 and 100 cm but it can reach a maximum TL of 150 cm (in Ref. ). The diet comprised crustaceans and molluscs. Early life stages were characterized by a benthic diet, which changed to benthopelagic during growth (in Ref. ).
2.23. Sandy ray—
Leucoraja circularisCouch, 1838
Demersal on sandy and muddy bottoms from the outer shelf and upper slope to 275 m depth, commonly found at 100 m depth (in Ref. ), maximum recorded size is 120 cm TL, but most individuals caught are between 70 and 80 cm TL (in Ref. [30, 65]). Its diet is poorly understood but it is most likely that it feeds on various bottom dwelling invertebrates, particularly crustaceans, and small teleost fish (in Ref. ). Species of local fishery importance are caught by bottom trawl fisheries.
2.24. Shagreen ray—
Leucoraja fullonicaLinneo, 1758
Demersal on rough ground on outer shelf and upper slope in about 30 to 550 m depth, maximum length is 120 cm; however, most specimens usually are 70 to 80 cm TL (in Ref. ). It feeds on a variety of bottom dwelling species but most probably prefers fish and crustaceans (in Ref. ). In the Mediterranean Sea, it is caught as bycatch by both bottom trawl and longline fisheries (in Ref. ).
2.25. Maltese ray—
Leucoraja melitensisClark, 1926
Maltese ray deep range is from 60 to 600 m. This small ray grows up to 50 cm TL (in Ref. ). It feeds on crustaceans mainly amphipods (in Ref. ). 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 (in Ref. ).
2.26. Cuckoo ray—
Leucoraja naevusMuller & Henle, 1841
Demersal on sandy and course bottoms on the shelf from 30 to 200 m depth, it is found on the continental shelf and slope at depths of 20–500 m (in Ref. ), but it is most common between 50 and 200 m depth (in Ref. ). The maximum TL is 75 cm for females and 68 cm for males (in Ref. ). Juvenile Cuckoo Rays feeds mainly on small crustaceans while adults also feed on polychaetes and bony fish (in Ref. ). Bycatch of bottom trawl fisheries (in Ref. ).
2.27. Starry ray—
Raja asteriasDelaroche, 1809
Starry skates are found predominantly on the Italian and Corsican continental shelves between shallow waters and 150 m depth. Maximum size is estimated at 72 cm TL and 76 cm TL for males and females, respectively (in Ref. ).
2.28. Blonde ray—
Raja brachyuraLafont, 1873
Demersal on sandy grounds from inshore to upper slope exceptionally as deep as 900 m, it reaches a maximum size of ∼120 cm (TL) and commonly reaches 40–100 cm TL (in Ref. ). Fish were a major prey item for all sizes of
2.29. Thornback ray—
Raja clavataLinneo, 1758
A relatively common skate from close in‐shore shallow waters to the outer continental shelf and upper slope from 10 to 300 m depth (in Ref. ), maximum‐recorded TL is 110 cm (in Ref. ). Thornback ray feeds mainly on teleosts, crustaceans and cephalopods, whereas gastropods and polychaetes are occasionally consumed (in Ref. ). In the Mediterranean Sea, the Thornback skate is frequently caught as bycatch in trawl fisheries targeting the Rose Shrimp (
2.30. Brown ray—
Raja miraletusLinneo, 1758
Demersal on soft bottom from shallow shelf to about 530 m depth, mainly at 50 to 150 m (in Ref. ),
2.31. Spotted ray—
Raja montaguiFowler, 1910
Demersal on soft substrate on shelf at 30–150 m depth, rarely as deep as 530 m, most individuals attain a TL of 40–60 cm (in Ref. ) and the maximum‐recorded TL is 80 cm (in Ref. ). For
2.32. Speckled ray—
Raja polystigmaRegan, 1923
2.33. Rough ray—
Raja radulaDelaroche, 1809
Rough ray occurs in coastal water up to 350 m depth (in Ref. ). Maximum size is about 50–60 cm TL (in Refs. [30, 76]). The diet of juvenile specimens of
2.34. White skate—
Rostroraja albaLacépède, 1803
White skate is a demersal species found on the continental shelf and upper slope from shallow water to 400 m, exceptionally to 500 m depth on sand and loose rocky substrate (in Refs. [30, 85]). Recorded maximum TL is 200 cm, though common between 60 and 150 cm of TL (in Refs. [34, 97]). Regarding diet aspect, it is known to prey mainly on fish and to lesser extent on crustaceans (in Ref. ). It is taken mainly as bycatch of bottom trawl fisheries (in Ref. ).
2.35. Marbled electric ray—
Torpedo marmorataRisso, 1810
Marbled electric ray lives in inner shelves on soft and stony bottom to about 40 m depth, rarely deeper to about 100 m (in Refs. [30, 65]).
2.36. Electric ray—
Torpedo nobilianaBonaparte, 1835
2.37. Common torpedo
—Torpedo torpedoLinnaeus, 1758
Mainly a benthic species found in near shore habitats and on soft bottoms, but also to about 70 m depth and occasionally deeper.
3. State of the art of
Chondrichthyesin South of Sicily
Among the seven orders of
Regarding batoids, another potential taxonomic misidentification could be related to speckled ray and spotted ray as well as to marbled stingray (
In conclusion, for many
In the investigated area, the analysis of the D.I. and B.I./D.I. temporal evolution from 1994 to 2013 highlights a slight recovery of sharks‐chimaera (Figure 2) while it seems to be in steady state for batoids (Figure 3).
Observing the temporal evolution of the sharks‐chimaera D.I. a stable trend is pointed out up to 2003, while a marked increment is underlined until 2008, while in the remaining five years, the D.I. seems fluctuate. Regarding batoids, the D.I. seems to fluctuate, although a clear increase is recorded between 2003 and 2010. The B.I./D.I. ratio seems more heterogeneous for batoids. This might be due to the different gear recruitment between the two investigated taxa as well as behaviour aspects (e.g. aggregation, swimming capability, feeding habits, etc.), relation with the bottom and life history traits. Detailed knowledge of elasmobranch habitat requirements is essential for biodiversity conservation and fisheries management, but this is often hampered by a poor understanding of their spatial ecology (in Ref. ). Indeed, the trends displayed above suggest that excluding the traditional considered rare species (such as
The spatial distribution of sharks‐chimaera in the GSA 16 (Figure 4) is mainly concentrated in the southern and north‐western zones. The D.I. distribution is characterized by several patches reaching values until 1600 N/km2, although in the north‐western a hotspot is recorded with values up to 2400 N/km2. This pattern mainly reflects the abundance and distribution of the small catsharks
Compared to sharks‐chimaera, the spatial distribution of batoids (Figure 5) is more circumscribed within two main zones, one biggest in the north‐western and the other in the southern part of the GSA 16. A small patch is recognized along the Sicilian coast with D.I. values up to 1200 N/km2. In the north‐western zone, higher values of D.I. (1600 N/km2) are recorded.
Taking into account the published data on fishing effort (F) recorded by vessel monitoring system (VMS) in the years 2006–2010 (in Ref. ), an astonishing overlap is observed between the highest rate of fishing effort and the lowest of D.I. for both taxa. The above‐mentioned considerations emphasize the importance to adopt an eco‐sustainable fishery in the near future, at least in the recorded zones with higher values of D.I.
The present results are in agreement with Ragonese et al. (in Ref. ) who reported that in the same investigated area, the state of sharks and chimaera seems quite stable or even improving (for some species). In the same area Gancitano et al. (in Ref. ), carried out a similar study considering all the cartilaginous fishes together. Similarly, a slight increase of D.I. trend was displayed from the first 2000s until 2008 although a marked increase is showed by two years forward predications (2014–2015).
In the central Mediterranean Sea, Lauria et al. (in Ref. ) implemented habitat models considering only species with percentage of occurrence (always using MEDITS data) >5% and defined as ‘Near Threatened’, ‘Vulnerable’, ‘Critically Endangered’ or ‘Data Deficient’ in the international union for conservation of nature (IUCN) Red Lists. The authors found a negative trend at a regional scale, mainly for rays (e.g.
The overexploitation of sharks has become an urgent Mediterranean ecological issue that requires an international management strategy able to take into account the biological, socio‐economic and ethical aspects to preserve the natural equilibrium of the marine ecosystem. Mitigation measures (such as the inclusion of excluder’s devices in the trawls or the release of caught or still living specimens) could be introduced for the reduction of fishing impact. A stronger effort should be sustained to educate fishermen for a responsible activity, as well as collaboration between enterprises and generally among the stakeholders, is highly recommended, also with the goal to define innovative technical solutions.
This work was carried out within the Data Collection Regulation and Framework‐module trawl surveys MEDITS funded by the European Union and the Italian Ministry of Agricultural, Food and Forestry Policies. We thank all the technical staff of CNR ‐ IAMC UOS of Mazara del Vallo (Italy) involved in data collection and processing.