Spatial and temporal distribution of cetaceans in the mid-Atlantic waters around the Azores

Abstract

Cetaceans living in offshore waters are under increasing pressure from anthropogenic activities. Yet, due to the lack of survey effort, relatively little is known about the demography or ecology of these populations. Spatial and temporal distribution of cetaceans in mid-Atlantic waters were investigated using a long term dataset collected from boat surveys and land-based observations around the Azores. From 1999 to 2009, 7307 cetacean schools were sighted during 271717 km of survey effort. In 4944 h of land-based observations, 2968 cetacean groups were detected. Twenty-four species were recorded: seven baleen whales, six beaked whales, eight dolphin species, Physeter macrocephalus, Kogia breviceps and K. sima. Overall, Delphinus delphis was the most frequently sighted species but its encounter rate decreased in JuneNovember, coinciding with presence of Stenella frontalis in the region. Tursiops truncatus, P. macrocephalus and Grampus griseus were frequently encountered yearround, whereas large baleen whales showed a distinct peak in encounter rates in March-May. Mesoplodonts were fairly common and appear to be present throughout the year. These findings fill-in a significant gap in the knowledge of cetaceans occurring in a poorly studied region of the North Atlantic, providing much needed data to inform management initiatives.

Sperm whale codas may encode individuality as well as clan identity

“…Groups of females, juveniles and calves are commonly observed in these waters and mature males are occasionally encountered (Matthews et al, 2001;Silva et al, 2014).…”

“…Sperm whales were studied during the summer of 2010 around the islands of Faial and Pico, in the Azores archipelago (38 N, 28 W), where they can be found year-round relatively close to the coast (Silva et al, 2003;Silva et al, 2014). Groups of females, juveniles and calves are commonly observed in these waters and mature males are occasionally encountered (Matthews et al, 2001;Silva et al, 2014).…”

Review of the Diversity, Ecology, and Conservation of Elasmobranchs in the Azores Region, Mid-North Atlantic

“…Evidence suggests that several charismatic species like marine birds (León et al, 2005), cetaceans (Silva et al, 2014), oceanic elasmobranchs Thorrold et al, 2014;Vandeperre et al, 2014bVandeperre et al, , 2016Queiroz et al, 2016), and fishes (Druon et al, 2016) use the archipelago as a feeding, mating, or breeding ground. Large cetaceans (Silva et al, 2014;Tobeña et al, 2016) and fishes (Kohler et al, 1998;Hilborn et al, 2010) alike frequent these waters during their seasonal migrations.…”

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“…Members of this family of deep diving whales display short breathing intervals at the sea 53 surface (Aguilar de Soto et al, 2012). Also, this speciose family shows large intraspecific variability in 54 colouration and interspecific similarities in general morphology, including in colour patterns (Mead, close to Faial island (Silva et al, 2014). In the Canary Islands, a 500 cm long male beaked whale 92 stranded in 1984 on the island of Lanzarote and was preliminarily identified as M. mirus due to itsgeneral morphology (Vonk & Martin, 1988).…”