The Aegean Sea supports some of the most important remaining marine mammal populations in the Mediterranean. Archipelagos´ marine mammal research team monitors year round through regular boat surveys the populations of Common Bottlenose dolphin (Tursiops truncatus), Short-beaked Common dolphin (Delphinus delphis), Stripped dolphin (Stenella coeruleoalba), Risso’s dolphin (Grampus griseus) and Sperm Whale (Physeter macrocephalus). Photo identification is used to identify individuals and record the frequency of which they are seen during boat surveys.
The short-beaked common dolphin is a species of particular interest to Archipelagos research. The last 30-50 years has seen a drastic 50% decline in individuals in the Mediterranean Sea, which has lead to the species being listed as ENDANGERED on the IUCN red list.
A resident population of the D.delphis are found in the marine region between the islands of Samos and the northern Dodecanese area. The Archipelagos marine mammals team monitors for the past years this population using photo identification during boat surveys.
The Short-beaked Common dolphin has a distinct yellow hourglass colouration along its side. Each individual of this species has a unique white pattern, similar to the fingerprint of humans, on its dorsal fin; thus, making it identifiable. In order to analyse the data, clear photos of the dorsal fin must be taken from side on.
A few examples can be found in the gallery below:
The photos taken during the boat surveys are then reviewed and compared to the database of previously identified individuals. The identification and addition to the catalogue of individuals aids with conservation as it allows the abundance of the species to be monitored.
Photo identification is also used for other species of cetacean such as the Common Bottlenose dolphin. However, T. truncatus does not have the markings that D. delphis does, instead the species can be recognised by the indents and notches on the dorsal fin. The software DARWIN can be used to identify the individuals by matching the outline of the dorsal fin and comparing it to the database of individuals already collected.
With these methods of identification for cetacean species, Archipelagos can continue with the conservation of the whales and dolphins in the Aegean Sea and monitor the population changes among the species.
Harry Kerr
BSc. in Marine Biology
University of Essex, England
