Introduction
Within the list of 88 chondrichthyan species (sharks, batoids and chimaeras) that are recorded in the Mediterranean 48% of species are regularly recorded, while 14% of species are becoming increasingly rare. The list includes 48 species of sharks belonging to 18 families, including Odontaspididae (Serena et al., Reference Serena, Abella, Bargnesi, Barone, Colloca, Ferretti, Fiorentino, Jenrette and Moro2020).
Until recently it was considered that family Odontaspididae was represented in the Mediterranean by two genera and two species: sand tiger shark Carcharias taurus Rafinesque, 1810 and smalltooth sand tiger Odontaspis ferox (Risso, Reference Risso1810). However, the latest taxonomy separates C. taurus from the Odontaspididae and assigns it to family Carchariidae, thus leaving O. ferox as the only Mediterranean species of Odontaspididae (Fricke et al., Reference Fricke, Eschmeyer and Van der Laan2022). The second member of family Odontaspididae is the bigeye sand tiger, Odontaspis noronhai (Maul, 1955), which occurs in the Indian, Pacific, and Atlantic oceans: this is arguably the most rarely captured extant lamniform species (Compagno, Reference Compagno2002).
Smalltooth sand tiger was first described from the Mediterranean Sea by Risso (Reference Risso1810), but is now known to have a cosmopolitan but disjunct distribution in warm-temperate and tropical waters of all oceans (Bonfil, Reference Bonfil1995; Fergusson et al., Reference Fergusson, Graham and Compagno2008).
Odontaspis ferox is a large, bulky shark that can reach a maximum total length of at least 450 cm. Distinguishing characteristics are a long, bulbously conical snout and moderately large teeth with prominent narrow cusps and two or more pairs of lateral cusplets. The second dorsal fin is smaller than the first dorsal fin but broad-based, while the first dorsal fin is closer to pectoral fins than pelvic fins. The colour is medium grey or grey-brown above, usually lighter below, sometimes with darker spots scattered on the body (Ebert et al., Reference Ebert, Dando and Fowler2021). It is reported on or near the bottom on continental and insular shelves and upper slopes at depths of 13–420 m. Reproduction is poorly known, and litter size unknown. Size at birth is over 105 cm, males mature at 200–250 cm and females at 300–350 cm (Ebert et al., Reference Ebert, Dando and Fowler2021).
Fergusson et al. (Reference Fergusson, Graham and Compagno2008) suggested a declining abundance of O. ferox, highlighting the vulnerability of the species to both accidental and directed fishing pressure. The species is listed by IUCN as Vulnerable globally (Graham et al., Reference Graham, Pollard, Gordon, Williams, Flaherty, Fergusson and Dicken2016) and Critically Endangered in the Mediterranean (Dulvy et al., Reference Dulvy, Allen, Ralph and Walls2016; Pollard et al., Reference Pollard, Gordon, Williams, Flaherty, Fergusson, Dicken and Graham2016).
During the 20th century, although O. ferox was recorded widely across the Mediterranean 14 records were observed by Fergusson et al. (Reference Fergusson, Graham and Compagno2008) while the MEDLEM (Mediterranean Large Elasmobranchs Monitoring) database contains only 10 records of O. ferox (Mancusi et al., Reference Mancusi, Baino, Fortuna, de Sola, Morey, Bradai, Kallianotis, Soldo, Hemida, Saad, Dimech, Peristeraki, Bariche, Clò, de Sabata, Castellano, Garibaldi, Lanteri, Tinti, Pais, Sperone, Micarelli, Poisson, Sion, Carlucci, Cebrian-Menchero, Séret, Ferretti, El-Far, Saygu, Shakman, Bartoli, Guallart, Damalas, Megalofonou, Vacchi, Bottaro, Notarbartolo Di Sciara, Follesa, Cannas, Kabasakal, Zava, Cavlan, Jung, Abudaya, Kolitari, Barash, Joksimovic, Marčeta, Gonzalez Vilas, Tiralongo, Giovos, Bargnesi, Lelli, Barone, Moro, Mazzoldi, Charis, Abella and Serena2020). Hence, only a very few records were made during the past two decades, these mainly from the Eastern Mediterranean (Corsini-Foka, Reference Corsini-Foka2009; Damalas & Megalofonou, Reference Damalas and Megalofonou2012; Kabasakal & Bayri, Reference Kabasakal and Bayri2019; Akbora et al., Reference Akbora, Bayri, Ayas and Çiçek2019). In the Adriatic, O. ferox and C. taurus were seen together at Croatian fishmarkets, albeit marketed under different names, during the last decade of the 20th century (Soldo, Reference Soldo, Basusta, Keskin, Serena and Seret2006). The last record of C. taurus from the Adriatic occurred in 1999, and O. ferox is now considered to be very rare in the Adriatic Sea (Lipej et al., Reference Lipej, De Maddalena and Soldo2004; Soldo & Lipej, Reference Soldo and Lipej2022).
This paper presents a rare observation of O. ferox: the northernmost Mediterranean record and the first in the Adriatic record for several decades.
Materials and methods
On 22 April 2021 a shark was landed dead at the Naval Base Pasha Liman, Bay of Vlore, Albania, Adriatic Sea (Figure 1). Videos recorded before it was landed show strange behaviours including slow swimming and rubbing against the shore installations. The shark was subsequently killed by Naval Base personnel. Length was estimated as about 300 cm by comparing the size of the shark in photos and videos to known fixed shore installations.
Fig. 1. Map of the area indicating (*) where the specimen was landed.
Species-level identification was not possible from photographs and videos. Fortunately, the head of the specimen had been preserved by the personnel of the Naval Base and identification was confirmed from the dry jaw and dentition.
Results and discussion
Photographic material shows a large, heavy-bodied female shark with conical to slightly depressed pointed snouts, long mouths extending behind small eyes, moderately long gill openings in front of pectoral fin origins, two large dorsal fins and an anal fin, small pectoral fins, and an asymmetrical caudal fin with a strong but short ventral lobe. These are characteristics of family Odontaspididae, but also Carchariidae, known to be represented in the Mediterranean by two species: Odontaspis ferox and Carcharias taurus (Ebert et al., Reference Ebert, Dando and Fowler2021). Key external characteristics that distinguish between these two species, such as the relative positions of the first dorsal fin and pectoral fin, were not visible. Furthermore, the freshly killed specimen had an unusual uniform chocolate brown colouration without dark spots on the sides of the body (Figure 2), which is considered a diagnostic feature of Odontaspis noronhai (Ebert et al., Reference Ebert, Dando and Fowler2021). Although O. noronhai has not been reported in the Mediterranean, it is so poorly known that its occurrence could not be excluded.
Fig. 2. Landed shark with uniform chocolate brown colouration without dark spots (photo by Sazan Pashollari).
Examination of the preserved head revealed that both upper and lower jaws have a pair of symphysial teeth. Most of the teeth have two cusplets on each side (Figure 3). The upper jaw starts with two anterior teeth much larger than sequential teeth, and has four rows of small intermediate teeth between anterior and lateral teeth. Lower jaw anterior teeth are larger than sequential teeth. These jaw and dental characteristics correspond with previous descriptions of O. ferox and distinguish it from the other two species (Bonfil, Reference Bonfil1995; Compagno, Reference Compagno2002; Tavares et al., Reference Tavares, Sanchez and Briceño2019; Pollerspöck & Straube, Reference Pollerspöck and Straube2020; Ebert et al., Reference Ebert, Dando and Fowler2021).
Fig. 3. Detail of the upper jaw.
Although the colouration is unusual for O. ferox, it is not unique; similar colouration was observed in a smalltooth sand tiger washed up on the beach at Agon-Coutainville, department of Manche, Normandy, France, in August 2012 (Ouest-France (2012), accessed online 25 March 2022).
This is the first record of O. ferox in the Adriatic for several decades. The species remains very rarely reported in the Adriatic and wider Mediterranean.
Data
The data that support the findings of this study are available from the corresponding author, [AS], upon reasonable request.
Acknowledgements
The authors thank the personnel of Naval Base Pasha Liman for the opportunity to examine the preserved head of the specimen. We are also grateful to Dave Ebert, Marc Dando and Mark Harris for helpful information.
Author contributions
All three authors formulated the research question, designed and carried out the study. Alen Soldo analysed the data and interpreted the findings while all three authors wrote the article.
Financial support
This research received no specific grant from any funding agency, commercial or not-for-profit sectors.
Conflict of interest
None.
Ethical standards
No approval of research ethics committees was required to accomplish the goals of this study because the specimen was examined by the authors when already dead.
