Behaviour of Delphinus delphis and Tursiops truncatus around Samos Island
Ship traffic has been increasing in the oceans in recent decades, especially in the northern hemisphere, and very likely will increase exponentially in the future. Anthropic activities produce diffuse and almost continuous noise that may affect very wide areas. Low-frequency (below 1,000Hz) ambient noise levels generated by ship traffic have increased in the northern hemisphere by two orders of magnitude over the last 60 years; their masking effect has therefore reduced the potential for long-range communication in cetaceans species.
Ubiquitous and continuous noise may have chronic effects, degrading the quality of marine habitats; even subtle effects, such as avoidance and signal masking, may have long-term population consequences if exposure is continuous.
The effects of sea traffic on animals can be described by considering both short- and/or long-term reactions. Short-term reactions are indicated by changes in behaviour and spatial movement away from the area of interaction.
Studying the behaviour of the dolphin population of the resident population of Short beaked dolphin (Delphinus delphis) and the Common bottlenose dolphin (Tursiops truncatus) around Samos island could show if the boat traffic is affecting their presence.
The Marine Mammal Team are conducting boat surveys every week to spot the dolphins and identify their behaviour. In a research initiated since 2016, Archipelagos is collecting year-round data with the aim to improve our understanding of these populations with knowledge that is essential for the conservation of these populations.
When dolphins are spotted, their behaviour is monitored each 3 minutes to assess changes, in relation to the presence of the various types of boats that are also in the area. The current results are showing a variegated ethogram about the two species. In these ethograms are included many surface behaviours that are no showing a negative impact on their presence. Even though this research is ongoing the waters of the NE Aegean are considered as a perfect habitat for the complex life of these amazing animals, which are important bioindicators of the health of the marine ecosystems.
Sebastien Saintignan (France)
MSc Observatoire des Sciences de l’Univers – Institut Pythéas Marseille