First underwater sighting of Shepherd’s beaked whale (Tasmacetus shepherdi)
Christopher Thompson, Jessica Meeuwig | Mar 21, 2019
Tasmacetus shepherdi observed on footage from mid-water stereo-BRUVS
Thompson CDH, Bouchet PJ, Meeuwig JJ. 2019. First underwater sighting of Shepherd’s beaked whale (Tasmacetus shepherdi). Marine Biodiversity Records, 12: 6.
Here we describe the first underwater sighting of Shepherd’s beaked whale (Tasmacetus shepherdi). Two individuals were observed together on video footage obtained via mid-water stereo-Baited Remote Underwater Video Systems (BRUVS) deployed off the coast of Inaccessible Island, Tristan da Cunha, in the South Atlantic. This observation constitutes the first recorded live sighting of this species in the waters of Tristan da Cunha since 2002 and provides further evidence for the persistence of a population of this species in the region. The observed individuals lacked the dark flipper stripe observed in previous descriptions, indicating that the species may exhibit greater variation in pigmentation than previous records indicate. The planned implementation of a marine reserve in the region along with the current low level of fishing pressure and remote location of this archipelago provide a good context to ensure the appropriate management and protection of this rare species. The recent establishment of an ongoing mid-water stereo-BRUVS monitoring programme, in concert with other methods targeted at marine mammals, may yield further information about this little known species and aid in informing management decisions in the future.
WHERE ARE THEY?
The top panel represents relative probabilities of occurrence (on a scale of 0 to 1) for Shepherd’s beaked whale derived from the relative environmental suitability (RES) model developed by (Kaschner et al. 2006). Low probability values are shaded in blue, and high ones in gold. The bottom panel is a map of published Shepherd’s beaked whale records within the Tristan da Cunha Island group and Gough Island. Both live sightings (gold) and reported strandings (white) are shown, with circle diameter proportional to group size. The sighting described in the present study is also denoted with a red outline. The depth surface is derived from General Bathymetric Chart of the Oceans (GEBCO) (Becker et al. 2009). Figure: Thompson et al. 2019.
RARE SHEPHERD’S BEAKED WHALE
Snapshot of footage from mid-water stereo-BRUVS collected off the south-east coast of Inaccessible Island, Tristan da Cunha. Key diagnostic morphological features indicated are: a robust rostrum tapered towards the tip, b prominent, bulbous and pale melon, c mask-like area of darker colouration surrounding the eye, d white throat patch, e white blaze above pectoral fins, f dark dorsal cape and g lightly pigmented caudal peduncle Figure: Thompson et al. 2019.
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