At the end of the 1970s, two unknown fish in the Italian seas were found stranded by one of us (F. Costa) on the shore of Cape Peloro, Strait of Messina (Figure 1). This area is well known to naturalists for its very strong up-sloping currents that periodically bring several bathyal organisms up to the surface and cause their strandings, thanks to a combination of biological, astronomical, atmospheric, hydrological, hydrodynamic and morphological factors (Berdar et al., Reference Berdar, Cavallaro, Giuffrè and Potoschi1977). Coastal species are stranded in this area as well due to the action of very strong tidal currents which may exceed 300 cm s−1 in speed (Mosetti, Reference Mosetti and Guglielmo1995).
Map showing the locality of the findings.
The two specimens were collected, photographed, measured and their meristic characteristics recorded. They were classified and frozen but, after incidental electricity blackout, they defrosted and got lost. The specimens correspond to Platycephalus indicus (Linnaeus, 1758) and Saurida undosquamis (Richardson, 1848), two lessepsian immigrant species not yet recorded in Italian waters. The original descriptions and pictures of these specimens are here reported.
The description of the specimen ascribed to Platycephalus indicus was the following:
Platycephalus indicus (16 cm TL) stranded at Cape Peloro (Strait of Messina) at the end of the 1970s.
‘Dorsal fin separated in two parts: the first one, nearly triangular, is short and bears spinous rays, the first of them being very short; the first part of the dorsal fin is barely connected to the second part that bears soft rays. Anal fin opposite and similar to the second part of the dorsal fin. Pectoral fins, moderately developed, inserted in correspondence of the opercular margin in almost ventral position. Ventral fins wide and elongated, scarcely surpass the anal aperture. Caudal fin wide, with straight posterior margin. Lateral line evident, slightly dorsal, bearing 73 scales.
Colour: dorsally sandy grey mixed with light brown with blackish variegation and a few dark stripes at regular distance. Whitish belly with unperceivable iridescence. Dorsal and anal fins are colourless except some traits of the first part of the dorsal fin bearing brown variegation. Ventral and pectoral fins bear evident variegation like dorsally. Three blackish sinuous stripes with feeble yellowish reflexes on the caudal fin. The eye is slightly elliptic (deep-set probably because in phase of exsiccation).
Total length: 16 cm. Meristic formula: D = X* + 13; A = 13; P = 19; V = I + 5. *Four spinous rays are broken at the base.
The specimen was in bad state of conservation probably due to the combined action of abrasion by sand and backwash effects.’
According to Knapp (Reference Knapp, Carpenter and Niem1999), the strongly flattened head bearing spines, the eyes partly directed upward, the lower jaw longer than upper and the insertion of pelvic fins behind pectoral-fin base, evident in the picture (Figure 2), ascribe this specimen to the Platycephalidae family and to the species P. indicus for the number of scales on lateral line together with the number of dorsal fin rays. Platycephalus indicus is a benthic fish frequently found on muddy and sandy bottoms in very shallow areas in estuaries and near shore to depths of about 25 m (Knapp, Reference Knapp, Carpenter and Niem1999); Fischer et al. (Reference Fischer, Bauchot and Schneider1987) report its occurrence also in rocky bottoms of continental shelf at depths to about 200 m. The common size of the species is 30–50 cm (Golani et al., Reference Golani, Orsi-Relini, Massutí, Quignard and Briand2002), but in the western Indian Ocean it is common to 60 cm, reaching a maximum length of about 100 cm (Fischer & Bianchi, Reference Fischer and Bianchi1984); our specimen of only 16 cm is, therefore, attributable to a juvenile. Platycephalus indicus is widespread from the Red Sea to South Africa, from the northern Indian Ocean to the western central Pacific eastward to Indonesia, Korea, southern Japan, Philippines, northern and eastern Australia (Knapp, Reference Knapp, Carpenter and Niem1999; Froese & Pauly, Reference Froese and Pauly2009). In the Mediterranean, it was recorded first in Israel (Ben-Tuvia, Reference Ben-Tuvia1953), successively in Egypt, Lebanon (Golani, 2002) and Syria (Saad, Reference Saad2005) and, currently, it remains confined to the Levantine Basin. Bilecenoglu et al. (Reference Bilecenoglu, Taskavak, Mater and Kaya2002) consider the unsubstantiated record of this species by Aksiray (Reference Aksiray1987) doubtful and, therefore, exclude its occurrence in Turkish waters. In the eastern Mediterranean, P. indicus is occasionally caught, in single specimens, by trawl (Ben-Tuvia, Reference Ben-Tuvia1966) or beach seine (El-Mor et al., Reference El-Mor, El-Etreby and Sapota2002). The unexpected record of one juvenile specimen so distant from its current geographical distribution and the absence of further findings let us suppose that it was transferred in the Strait of Messina through ballast waters and then stranded by the strong currents typical of this area.
The specimen identified as Saurida undosquamis was described as follows:
Saurida undosquamis (15.4 cm TL) stranded at Cape Peloro (Strait of Messina) at the end of the 1970s.
‘Body slender and cylindrical except in the extreme posterior part that is compressed; large mouth, deeply cleft, with numerous series of very sharp teeth on both jaws, on tongue and palatines. A nearly triangular dorsal fin midway on back; a moderately short adipose dorsal fin; moderately wide anal fin opposite to the adipose fin. Ventral fins insertion anterior to that of the dorsal fin. Pectoral fin in proximity of the opercular margin, in medial position. A well developed forked caudal fin with pointed lobes. Fifty-one scales on the poorly evident lateral line along which eight apparently faded dark spots regularly distanced to each other.
Colour: dorsally pale grey with silvery belly; moderately small circular bright silvery eye. All the fins are transparent except the dorsal and the caudal ones with anthracite grey margins.
Total length: 154 mm. Meristic formula: D, 11; A, 10; P, 15; V, 9.
The specimen was in a good state of conservation except for lacking many scales, probably due to the combined action of abrasion by sand and backwash effects.’
The characters recorded correspond as well as those of the family Synodontidae, represented in the Mediterranean by only two genera: Saurida and Synodus. Pelvic fins with nine rays distinguish the former from the latter, which has only eight (Russell, Reference Russell, Carpenter and Niem1999).
Saurida undosquamis is a piscivorous species, widely distributed in the Indo-Pacific from the Red Sea and East Africa to Australia and Japan (Fischer & Bianchi, Reference Fischer and Bianchi1984). In the Mediterranean, it was first recorded in Israel (Ben-Tuvia, Reference Ben-Tuvia1953), then the population exploded spreading northward to the waters of Cyprus, Turkey, Dodecanese, Crete, Greece, Albania and westward to Egypt, Libya (Golani, 2002) and Tunisia (Ben Souissi et al., Reference Ben Souissi, Trigui El Menif, Mahjoub, Méjri, Quignard, Capapé, Zaouali and Özhan2005).
This species occurs on sandy and muddy bottoms in depths of 20–350 m (Russell, Reference Russell, Carpenter and Niem1999). It attains 50 cm but it is common until 20–30 cm (Fischer & Bianchi, Reference Fischer and Bianchi1984); males and females, in Turkish waters, attain maturity at about 16 cm and 16.5 cm TL respectively (Işmen, Reference Işmen2003), although Gökçe et al. (Reference Gökçe, Sangün, Özbilgin and Bilecenoglu2007) report higher sizes of mean length at first maturity in the same area. Our specimen of 15.4 cm is, therefore, classifiable as maturing. Saurida undosquamis is a successful invader, well established and commercially important in the eastern Mediterranean (see Abdallah, Reference Abdallah2002; Işmen, Reference Işmen2003; Akyol et al., Reference Akyol, Kinacigil and Şevik2007; Shakman & Kinzelbach, Reference Shakman and Kinzelbach2007). It has been listed among the 100 worst invasive species in the Mediterranean and has serious impact on biodiversity (Streftaris & Zenetos, Reference Streftaris and Zenetos2006).
Similar to Platycephalus indicus, Saurida undosquamis has not been recorded in the Italian seas yet. Consequently, the individual found more than 27 years ago at Cape Peloro could be considered as a stray specimen. Although the hypothesis of natural dispersion would be supported by the high dispersal speeds reported for this species in the literature (Ben Rais Lasram et al., Reference Ben Rais Lasram, Tomasini, Guilhaumon, Romdhane, Do Chi and Mouillot2008), that one of ship-mediated transfer can not be discarded. In the Mediterranean, such transport is suggested for at least three non-native fish species (i.e. Pinguipes brasilianus, Sargocentron rubrum and Abudefduf vaigiensis) and seems underestimated because of the fragmented documentation (CIESM, 2002).
ACKNOWLEDGEMENTS
The authors are grateful to Patrizia Perzia and Tiziana Cillari for technical assistance and to three anonymous referees whose critical comments improved the manuscript.
