English - Caribbean Environment Programme

Juveniles have been sighted in this region between March and November 387 . Off the north eastcoast of Lewis, whole groups comprised exclusively of sub-adults or juveniles were noted onseveral occasions, and a group consisting of eight females, each with a calf, has also beenobserved 388 . Sightings such as these strongly suggest this area has importance for breeding,nursing and/or raising young.North east Lewis is the focus of Risso's dolphins activity in this area but high sightings rates arereported for the rest of the western part of the Hebrides during the summer and there may befurther areas of importance in these less studied waters.There are generally few data available about Risso's dolphins in more offshore waters but sightingsoccur mostly during autumn and winter and are concentrated along the continental slope 389 .Sightings are too few to suggest particular areas of importance.Coastal Wales and the Irish SeaCertain locations in the Irish Sea – the Isle of Man, Anglesey, Bardsey Island and the LleynPeninsula, and Pembrokeshire – record Risso's dolphin sightings relatively regularly 390 . BardseyIsland records the highest sightings rates, followed by northern Pembrokeshire 391 .The waters off Bardsey Island in North Wales have been subject to a small-scale, multi-year studyof its cetacean fauna and this has confirmed the area’s importance for Risso's dolphins 392 . Despitebeing predominantly a land-based survey, 133 individual Risso's dolphins have been catalogued,with a few resightings between years 393 . The survey has been conducted in April, July, August andSeptember and Risso's have been observed in every month. Bardsey Islanders report seeingRisso's at other times also but it is unknown whether Risso's are present all year round in coastalwaters, present all year but further offshore or only seasonally present.As in the Isle of Lewis study, Bardsey Island researchers have observed groups containing onlysub-adults and 'nursery groups' consisting of multiple females, each with a calf. High numbers ofyoung animals are seen here; 10% of photographed Risso's dolphins have been calves andjuveniles and 29% were identified as sub-adults 394 . Some apparently very young calves have beenobserved, including one with foetal folds 395 . These observations indicate that the area is importantto Risso's dolphins for breeding, nursing and/or raising calves.Behaviour indicative of feeding (such as deep dives or remaining submerged for a long period) hasbeen observed often around Bardsey 396 and prey availability is likely a driver for them being in thearea. It has been suggested that the complex topography and deep ocean trenches around Bardseymay create areas of upwelling with increased productivity that Risso's dolphins exploit 397 . The lesseroctopus, known prey for Risso's dolphins from stomach studies of stranded animals found in Walesand Scotland 398 , is found in the trenches offshore and reportedly comes inshore to lay its eggs onthe horse mussel reefs in this area 399 . Risso's dolphins have been sighted feeding over thesereefs 400 , possibly following their prey inshore.There is much less information available for the other locations in the Irish Sea where Risso'sdolphins are sighted. Young have been observed off Pembrokeshire and Anglesey between Julyand September 401 but beyond this, the relative importance of these locations is unclear.Further research on Risso’s dolphins is needed in the waters of north east Lewis andBardsey Island to improve our knowledge of these important populations. Expanding thephoto-ID catalogues in the surrounding areas will help us understand the wider-scalemovements and possible connections between these populations.48387Pollock et al, 2000388Atkinson et al, 1998389Reid et al, 2003; Pollock et al, 2000390Evans et al, 2003391Baines and Evans, 2009392WDCS, 2002, 2003, 2004, 2005a and 2006; De Boer, 2009393De Boer, 2009394Ibid395WDCS, 2004396WDCS, 2005a397Wharam and Simmonds, 2008398Atkinson et al, 1998; Wharam and Simmonds, 2008399Wharam and Simmonds, 2008400Ibid401Baines and Evans, 2009