English - Caribbean Environment Programme

Figure 4.13 (below) is the estimated density surface for common dolphins produced fromSCANS II 240 .Results from the CODA survey which took place beyond the shelves of the UK, Ireland, Franceand Spain are displayed in Figures 4.14 (below) and 4.15 (p.37) 241 .Far west and west ScotlandThe more northerly CODA block and the SCANS II sector over the continental shelf to the westof the Hebrides both reported low densities of common dolphins (0.01 animals/km 2 for both)(see Figures 4.12, p.35 and 4.14, above). No data are currently available about common dolphinabundance for the north west sector of UK waters. Surveys of the area of sea immediatelysouth of this sector have recorded very high densities of common dolphins during the summer,1.36 animals/km 2 and an abundance of 273,159 animals (95% CI 153, 392 - 435,104) in thesurvey area 242 . It may be that this region of high density extends north into UK jurisdiction andsurvey work will be needed to confirm this (see Figure 4.16, p.37).Common dolphins are seen in the inshore waters of the Hebrides mainly during the summer.The SCANS II survey found moderately high densities here (0.0758 animals/km 2 ), and anabundance of 2,322 animals in this small area 243 . In other studies here, this species is reportedas common in the summer, particularly in the Sea of the Hebrides 244 . Observations of themfeeding in the waters of The Minch have been made, as have the presence of calves, raising thepossibility that they use the area to breed and nurse young 245 . There is some evidence that theirnumbers are increasing in this area and this is thought to be due to rising sea temperatures 246 .If this trend continues, the area may become increasingly important for common dolphins.Although the results from SCANS and CODA indicate that the area further offshore of theHebrides may have lower densities of common dolphins in the summer, some studies reportnotable concentrations over the shelf edge and beyond for the autumn months 247 . Data aresparse at this time of year but there are indications that the north east Rockall Trough andadjacent continental slope area, along with the Rosemary Bank, may be particularly used bycommon dolphins. Shelf-edges and offshore banks are often areas of increased productivityso their importance may be as foraging habitat.36240Reproduced with permission. SCANS II, 2006. Please note that density surface maps show estimated densityderived from a spatial model and should not be overinterpreted, particularly at a fine spatial scale.241Reproduced with permission. CODA, 2009. Please note that density surface maps show estimated densityderived from a spatial model and should not be overinterpreted, particularly at a fine spatial scale.242Cañadas et al, 2009243SCANS II, 2006244Reid et al, 2003; HWDT data (in Hammond et al, 2006)245Weir et al, 2009246Ibid247Pollock et al, 2000; MacLeod, 2001; Reid et al, 2003