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One of the least known dolphin species is the Southern Right Whale Dolphin Lissodelphis peronii, which Best et al. (2009) reported based on the capture of a single animal by a whaling ship about 60 km east of Tristan on 10 December 1847. I was thus very excited to encounter a group of about 70 of these spectacular animals roughly midway between Nightingale and Tristan on 29 September 2014. The pod ran in front of the S.A. Agulhas II for a few minutes, before moving away from the ship. It was just more than 30 years since my only previous sighting of this elusive animal, off Marion Island in August 1984.
On discussing the record with friends in Cape Town, it emerged that there was another record from Tristan waters, albeit farther from the islands. In April 1989, Barrie Rose was aboard the South African fisheries research vessel Africana II, conducting research around Tristan. On 24 April he observed a pod of at least 100 Southern Right Whale Dolphins, loosely associated with Long-finned Pilot Whales Globicephala melas and Bottle-nosed Dolphins Tursiops truncatus at 39 ° 49.5 ¢ S 12 ° 58.8 ¢ W, roughly 300 km south of Tristan and 260 km WNW of Gough Island. Presumably the same group of animals was seen the following day 160 km farther south at 41 ° 21.4 ¢ S 13 ° 01.8 ¢ W. On this occasion they remained with the ship (which was on station at the time) for more than 30 minutes, twice sounding for 6-8 minutes at a time. Interestingly, this appears to be the first record of Bottle-nosed Dolphins from Tristan waters!
With their striking colouration, extremely long, slender bodies and no dorsal fin, Southern Right Whale Dolphins are easy to identify. It thus likely that they are genuinely scarce visitors to Tristan waters.
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