Cetaceans in Greece: Present status of knowledge

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Reported sightings and strandings There are 38 sightings of Risso’s dolphins recorded in the Greek Seas, mainly spread all over the Aegean Sea. All the sightings in the Gulf of Corinth concern repeated observations of the same two photo-identified individuals. Strandings of Risso’s dolphins are not rare in Greece, although much less frequent than those of all other resident dolphin species (Table 1). The 34 strandings reported here are spread homogeneously in the Ionian, Aegean and Cretan Seas. Geographic range The distribution of the recorded sightings and strandings of Risso’s dolphins in the Greek Seas seems to be homogeneous and indicates that the species may be present in all parts of the Greek Seas. However, there is only one known area where Risso’s dolphins can be predictably found and this is the Myrtoon Sea south to the NW Crete. The sightings made in SW Crete come from the years 1998 and 1999, but despite the continuous effort no other sightings were made in this area until the end of 2008. The sightings in the Gulf of Corinth all come from the same two photo-identified individuals first observed in 1997 (Frantzis & Herzing 2002). Two other areas where sightings and strandings have been recorded are the Northern Sporades and the sea area of the Chalkidiki Peninsula. Surprisingly, no Risso’s dolphins have been observed in the Ionian Sea, despite intense survey effort during more than a decade. However, the species occurs in the area, since nine strandings (two of which were live animals) have been recorded from the N Corfu to S Peloponnese. Apparently the species is present in low numbers or out of the warm season, when all the survey effort is concentrated. Eight strandings in the Ionian Sea have been recorded from the end of September to late April, and one in June. Sightings and strandings of Risso’s dolphins have also been recorded in the relatively shallow area of the Cyclades Islands. Habitat Risso’s dolphins have been observed mainly in the slope habitat, but also close to the coast and over the Aegean plateau, like in the Cyclades. This explains why the average depth of observations is less than that of sperm whales and the Cuvier’s beaked whales. This is also due to the fact that the depressions in the Aegean Sea (where many of the sightings come from) have shallower depths than along the Hellenic Trench (where few observations are available for this species). The mean water depth and distance from the coasts of 37 Risso’s dolphin sightings is 737 m (range 165-171 m; sd=380) and 8.2 km (range 0.3-28.32 km; sd=5.8), respectively. It is probable that Risso’s dolphins are present farther offshore, over the abyssal plains, at least in the Levantine Sea (Song of the Whale Research Team 2007). In the western Mediterranean Risso’s dolphins show a preference for deep pelagic waters, in particular over steep shelf slopes and submarine canyons (Gaspari and Natoli 2006, Azzelino et al. 2008). Abundance There are no available data on the abundance of this species in the Greek Seas. The stranding and sighting numbers indicate that it is much less abundant than striped dolphins, common bottlenose dolphins and short-beaked common dolphins, and probably more 36
abundant than fin whales and harbour porpoises. No abundance estimates are available for the Risso’s dolphins in the Mediterranean, except for a small zone covering 32.000 km 2 off the Valencian coasts in Spain (Gómez de Segura et al. 2006), where the estimate was 493 animals. In all surveyed areas in the Western Mediterranean, encounter rates have been variable but generally low (i.e. 0.1-0.2 encounters per km; Gaspari and Natoli 2006). Population trend Population trends are unknown, both at the regional and local level. Degree of residency and/or isolation Information from strandings and sightings suggests that Risso’s dolphins may be present in Greek waters year-round. However, they may be seasonal in the Ionian Sea, where strandings (including live animals) were recorded almost exclusively during the cold months (end September – late April). Risso’s dolphins in the Mediterranean Sea are genetically differentiated from those in the eastern Atlantic and some evidence exists of population structure within the Mediterranean (Gaspari et al. 2006). Seasonality of reproduction No data are available from the Greek Seas or the Mediterranean, and no neonates were included in the stranding record. A young animal of 1.73 m stranded in late November and another, approximately 1.7 m long, stranded in late June. A calf was observed at sea in mid August. Feeding habits The diet of Risso’s dolphins is based on squid and occasional fish (Kruse et al. 1999). In two stomach contents from Greece there were several unidentified squids and squid remains, and one stomach contained the entire skeleton of a largehead hairtail Trichiurus lepturus about 85-90 cm long. Only one squid beak was found in the stomach of a third Risso’s dolphin that was apparently sick while observed for several days before it died and stranded. Main threats Entanglement in longlines or nets was the cause of death for at least four stranded animals. Bycatch in fishing gear has also been reported to occur elsewhere in the Mediterranean (Gaspari and Natoli 2006). The stomach of one adult that stranded alive was full of plastic debris. 37
Page 1 and 2: Cetaceans in Greece: Present status
Page 3: Organisations supporting the Initia
Page 7: ORIGIN AND SCOPE OF THIS REPORT The
Page 10 and 11: According to the distribution maps
Page 12 and 13: not belong to the suborder of mysti
Page 14 and 15: Data collection Available cetacean
Page 16 and 17: from the network was initially cons
Page 18 and 19: Distribution and effort The distrib
Page 20 and 21: Sighting data Ten cetacean species
Page 23: CETACEAN SPECIES COMMONLY OCCURRING
Page 26 and 27: Reported sightings and strandings T
Page 28 and 29: Main threats In the western Mediter
Page 32 and 33: published stomach content contained
Page 36 and 37: the stranding and death of several
Page 40 and 41: IUCN Red List classification Medite
Page 45 and 46: Drawing by Massimo Demma / ICRAM Ta
Page 47 and 48: Degree of residency and/or isolatio
Page 49 and 50: Drawing by Massimo Demma Taxonomy D
Page 51 and 52: a similar abundance. Short-beaked c
Page 53: 2008b). No information is available
Page 58 and 59: important: anchovy, sprat (Sprattus
Page 61 and 62: Megaptera novaeangliae (Borowski, 1
Page 63 and 64: Balaenoptera acutorostrata Lacépè
Page 69 and 70: Steno bredanensis (G. Cuvier in Les
Page 71 and 72: FALSE REPORTS OF CETACEAN SPECIES I
Page 73 and 74: WHAT IS KNOWN, WHAT REMAINS UNKNOWN
Page 75 and 76: ARE THE GREEK CETACEAN POPULATIONS
Page 77 and 78: ACKNOWLEDGEMENTS Many thanks to sev
Page 79 and 80: Bearzi G., Politi E., Agazzi S., Az
Page 81 and 82: García-Martinez J., Barrio E., Rag
Page 83 and 84: Notarbartolo di Sciara G., Demma M.
Page 85 and 86: ANNEX I: Distribution of searching
Page 87 and 88: Balaenoptera physalus FIN WHALE (Π
Page 89 and 90:
Ziphius cavirostris CUVIER’S BEAK
Page 91 and 92:
Tursiops truncatus COMMON BOTTLENOS
Page 93 and 94:
Delphinus delphis SHORT-BEAKED COMM
Page 95 and 96:
ANNEX III: Additional references on
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Cetaceans in Greece: Present status of knowledge

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