The little-known Fraser’s dolpin Lagenodelphis hosei in the North Atlantic: new records and a review of distribution

摘要

The distribution of the poorly known Fraser’s dolphin Lagenodelphis hosei Fraser (Sarawak Mus J 7:478–503, 1956), is revised for the northern Atlantic (NA), with new records for temperate and subtropical oceanic islands. Fraser’s dolphins are reported for the first time in the Azores, from a pod of approximately 50 individuals observed in August 2008, and for the Madeira Archipelago, where a pod of circa 80 individuals is described from opportunistic observations in August 2010. Observations in the Azores occurred during a period of regional increase in seawater temperature (23.5 °C; >1 °C for circa 15 days), revealing the species potential as a bio-indicator of climate change. The occurrence of Fraser’s dolphins in the NA is characterized by an equally small number of stranding events and sightings at sea which have been accumulating since 1972. A compilation of 47 occurrences from publications, reports and online databases (plus one report with 123 sightings in the Lesser Antilles), was used to comment on the species ecology in the region. Stranding events are often of a single specimen, occurring on both western and eastern margins. Sightings at sea are scattered throughout the NA, with most observations from the Gulf of Mexico, and the Caribbean Sea, where year-round sightings have been reported in the Lesser Antilles (off Guadeloupe). Observations are mostly confined to open waters over 200–2,200 m depth areas, approaching the coasts of oceanic islands. Pod sizes vary between 50 and 80 in the Caribbean Sea, with smaller pods observed in the Gulf of Mexico (15–30), only rarely exceeding 100 individuals per group (20 %, n = 5), in contrast to large aggregations reported in the Pacific. Captures have been reported from St. Vincent (Lesser Antilles) and more recently from Ghana. Mixed-species groups have been observed, such as with Peponocephala electra and Globicephala macrorhynchus. Knowledge of Fraser’s dolphin ecology in the NA is expected to grow with increasing surveys in the Caribbean area and tropical latitudes. Reports on the species occurrence, such as data from opportunistic platforms, should continue to reach the scientific community, including with associated environmental data.