Detecting toothed whales and dolphins in the Hellenic Seas
The Ionian and Aegean Seas, both part of the eastern Mediterranean Sea, are habitat for several odontocete species including striped (Stenella coeruleoalba), short-beaked common (Delphinus delphis), Risso's (Grampus griseus), and bottlenose (Tursiops truncatus) dolphins as well as Cuvier’s beaked (Ziphius cavirostris), and sperm (Physeter macrocephalus) whales. Common dolphins and sperm whales in the study area are listed as endangered in the IUCN Red List of Threatened Animals. Furthermore, several standings of Cuvier’s beaked whales in Greece have been linked to naval sonar exercises. Currently, very little is known about the seasonal abundance and distribution of cetacean species in the eastern Mediterranean Sea. This information is crucial for the development of effective protection measures for these animals.
In a first attempt to collect baseline data on the occurrence patterns of odontocetes in Greek waters, two passive-acoustic recorders were deployed in 2008 in the Ionian Sea in the vicinity of Ocean Station Pylos (36.8N, 21.6E) and in the northern Aegean Sea in the vicinity of Ocean Station Athos (40.0 N, 24.7E). These recorders operated for 19 and 10 months, respectively. The data analysis is focused on the detection of delphinid species and sperm whales at both locations and their seasonal presence. Current work is orientated towards species identification of delphinid whistles using the Real-time Odontocete Call Classification Algorithm (ROCCA) to allow an analysis of species-specific occurrence patterns. Future work will include an examination of oceanographic data collected at each site (http://poseidon.hcmr.gr) to identify environmental drivers of the occurrence of odontocetes in the Ionian and Aegean Sea.
Work supported by the Hellenic Centre for Marine Research and the University of the Aegean, Greece.