Cetaceans in the central Mediterranean Sea: Distribution and sighting frequencies

Abstract

Abstract From 1986 to 1989 a series of cruises were conducted in the central Mediterranean Sea, to determine distribution and relative abundance of cetaceans. Observation sessions lasted for a total of 2433 h. The presence of animals was assessed visually. Relative sighting frequencies among species and among subdivisions of the study area were calculated, based on observation time. Seven species were observed, including, in order of decreasing frequency: bottlenose dolphins (Tursiops truncatus), striped dolphins (Stenella coeruleoalba), fin whales (Balaenoptera physalus), sperm whales (Physeter catodon), Risso's dolphins (Grampus griseus), common dolphins (Delphinus delphis) and long‐finned pilot whales (Globicephala melas). The highest sighting frequencies occurred in the Ligurian‐Corsican Sea; cetaceans were scarcest in the Tyrrhenian Sea and in the northern Adriatic Sea. Bottlenose dolphins were found throughout the study area in neritic waters. Fin whales, sperm whales, Risso's dolphins, and striped dolphins were sighted in the offshore waters of the Ligurian‐Corsican, Tyrrhenian, and Ionian Seas. The now rare common dolphin was mostly seen in the Sardinian Sea, in the Sicily Channel, and in the Ionian Sea. Pilot whales were observed, occasionally, in the Ligurian‐Corsican and Tyrrhenian Seas.