Summer Distribution, Relative Abundance and Encounter Rates of Cetaceans in the Mediterranean Waters off Southern Italy (Western Ionian Sea and Southern Tyrrhenian Sea)

Abstract

During the summers of 2010 and 2011, weekly cetacean surveys were undertaken in "passing mode", using ferries as platforms of opportunity, along the "fixed line transect" between Catania and Civitavecchia (southern Italy). Of the 20 species of cetaceans confirmed for the Mediterranean Sea, eight were sighted within the survey period, of which seven species represented by Mediterranean subpopulations (Balaenoptera physalus, Physeter macrocephalus, Stenella coeruleoalba, Delphinus delphis, Grampus griseus, Tursiops truncatus and Ziphius cavirostris) and one is considered a visitor (Steno bredanensis). A total of 220 sightings were effected during 2010 and a total of 240 sightings in 2011. The most frequently recorded species was S. coeruleoalba. By the comparing the data from the two sampling seasons, a significant increase of D. delphis sightings and a decrease of sightings of B. physalus and P. macrocephalus were observed. While all the other species were observed in both sampling seasons, Z. cavirostris and Steno bredanensis were observed only during 2011. The presence of mixed groups of odontocetes was also documented: groups composed of pairs of species were S. coeruleoalba and D. delphis, S. coeruleoalba and T. truncatus, and S. coeruleoalba and G. griseus. The results of this research add useful information on cetacean species in a very poorly known area and highlight the need to standardize large-scale and long-term monitoring programs in order to detect variation in presence, abundance and distribution of cetaceans populations and understand the effect of anthropogenic factors.

Prvi dokumentirani zapis o Tetragonurus cuvieri Risso, 1810. (Perciformes, Stromatoidea) duž kalabrijskih obala (Južna Italija, Središnji Mediteran)

“…Since our specimen was a mature/spawner male and it has been caught at -7 m depth without any clear sign of decompression phenomena, and considering that the Tyrrhenian has been demonstrated to be a spawning area (BERDAR et al, 1982) for the species, we could speculate that it had risen to the surface to reproduce. This record confirms the importance of the Calabrian Tyrrhenian Sea as a reproductive and a migration area for many vulnerable, rare or little-known animal species between the eastern and western Mediterranean (SANTORO et al, 2015;SPERONE & MILAZZO, 2018;SPERONE et al, 2019).…”

Influence of seasonality on cetacean diversity, abundance, distribution and habitat use in the western Mediterranean Sea: Implications for conservation

“…Associations in mixed‐species groups were recorded three times, and always with few individuals within striped dolphin pods, as most commonly reported (Cañadas & Hammond, ; Frantzis & Herzing, ; Pace, Mussi et al ., ). This kind of association is probably determined by the relative low abundance of common dolphins that, when they cannot form single species groups, tends to move and depend on striped dolphin schools (Frantzis & Herzing, ); conversely, in the southern Tyrrhenian basin where the species is more abundant (Pace, Mussi et al, ), occurrences of mixed groups were less frequent (Santoro et al ., ).…”

The conservation of the endangered Mediterranean common dolphin (Delphinus delphis): Current knowledge and research priorities

“…A latitudinal gradient in the frequency of mixed-species groups with striped dolphins (S. coeruleoalba) was also reported (Arcangeli et al, 2017;Pace et al, 2015). In the southern Tyrrhenian Sea, including the Strait of Messina, the species occurrence is reported to be higher (Pace et al, 2015(Pace et al, , 2016Santoro et al, 2015), but no abundance estimates are available. Records of D. delphis have been documented in other Italian waters (Mussi et al, 2016;Pace et al, 2016Pace et al, , 2019, in the Pelagos Sanctuary (Pace et al, 2015), Ischia Island (Mussi et al, 2021;Mussi & Miragliuolo, 2003, near Lampedusa Island (Pace et al, 2015), off western Sardinia (IUCN, 2017), at Cap Bon, north-east Tunisia (Aissi & Vella, 2015;Benmessaoud, Chérif, Bradai, & Bejaoui, 2012), in the eastern Ionian Sea (Frantzis & Herzing, 2002), in the Aegean Sea (Dede & Öztürk, 2007;Giannoulaki et al, 2017;Ryan et al, 2014), in the Levantine Sea (Boisseau et al, 2010;Brand et al, 2021;Kerem et al, 2012), in Libyan waters (Benamer, 2016), and along the Algerian west coast (Larbi Doukara, 2021;Larbi Doukara, Bouslah, Bouderbala, & Boutiba, 2016) and the Moroccan coast (Masski & De Stephanis, 2015).…”