Cetaceans in Greece: Present status of knowledge

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abundances for any species in the entire Greek Seas. Research aimed to produce abundance estimates and trends is of high priority. Cetacean conservation demands the careful design and application of management measures for each species that will guarantee the survival of a population large and healthy enough to prosper. At present, however, there is no possibility of testing the effectiveness of any management measure, except for a very few areas, due to the unknown abundance and status of most populations. Although there has been progress in our knowledge on cetaceans inhabiting the Greek Seas during the last 15 years, we are still far from understanding the complexity of their ecology, and in most cases we remain unable to monitor their status. Given the gaps in the current knowledge regarding cetacean populations in Greece, there is still a lot of scientific work needed so that conservation efforts can start to be effective at the national level. 72
ARE THE GREEK CETACEAN POPULATIONS DECLINING? The data of this report and previous studies have shown that eight cetacean species inhabit the Greek Seas. Crucial data on the abundance and the population status and trend of these species at the national level are not available. However, information from portions of the Greek Seas and the rest of the Mediterranean Sea suggest that most cetacean species populations are likely to be declining, some even at alarming rates. Perhaps the most revealing example is that of the short-beaked common dolphin. Once one of the commonest species in the Mediterranean Sea, common dolphins have experienced a generalised and major decrease in this region during the last 30-40 years (Bearzi et al. 2003). At least in the inner Ionian Sea, overfishing of this species’ prey has caused its dramatic rarefaction (Bearzi et al. 2008b). Overfishing is known to occur in many other parts of the Greek Seas, with a continuous decline of fish biomass since the mid 90s (Stergiou 2005, Stergiou et al. 2007, Machias et al. 2007). As a result, depletion of key cetacean prey can be expected. While the rate of population decrease may vary from one area to another, the alarmingly rapid decline of common dolphins in the inner Ionian Sea (Bearzi et al. 2008b) suggests that important cetacean populations can rapidly disappear from the Greek Seas. Prey depletion is one of the threats that may drive the apparently small population unit of the Aegean harbour porpoises to decline and potentially to extinction. In the north Aegean this species lives at the limit of the highest temperatures it can afford (Poulos et al. 1997, Read 1999); therefore, increasing sea surface temperatures in the Aegean Sea (V. Papathanasiou, pers. comm.) may threaten its survival. The population of sperm whales in the Greek Seas is also very small (Pelagos Cetacean Research Institute, unpublished data). Populations of a few hundreds of individuals may disappear even by natural changes in their environment. In the case of sperm whales in Greece, mortality caused by ship strikes alone seems unsustainable, and further threatens this small population (Pelagos Cetacean Research Institute, unpublished data). Ingetsion of plastic debris is yet another anthropogenic cause of mortality. The population trend for common bottlenose dolphins and striped dolphins in the Greek Seas are unlikely to differ significantly from trends in the whole Mediterranean region. Such trends are thought to be negative for bottlenose dolphins (Bearzi et al. 2008c), and was very negative in the last two decades, but currently uncertain for striped dolphins (Aguilar 2006). 73
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Cetaceans in Greece: Present status
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Organisations supporting the Initia
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ORIGIN AND SCOPE OF THIS REPORT The
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According to the distribution maps
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not belong to the suborder of mysti
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Data collection Available cetacean
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from the network was initially cons
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Distribution and effort The distrib
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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: WHAT IS KNOWN, WHAT REMAINS UNKNOWN
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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