Research Results
Four years of data collection have established an important baseline for understanding the current large-scale distribution and abundance of cetaceans in the Hebrides and monitoring changes that occur over time.
In 2008, over 500 sightings were made, totalling 1216 individuals which included 788 harbour porpoises (Phocoena phocoena), 50 minke whales (Balaenoptera acutorostrata) and 12 orca (Orcinus orca). For some species, such as minke whale, bottlenose dolphin (Tursiops truncatus), Risso’s dolphin (Grampus griseus) and basking shark (Cetorhinus maximus). Photographs of individually distinctive natural markings, such as marks and scars on the dorsal fin, fluke and body, serve as a natural tag for identifying individuals. When these animals were encountered, high quality identification photographs were taken and added to Hebridean Whale and Dolphin Trust’s catalogues, as well as being sent to the Europhlukes project - a Europe-wide repository for cetacean photo identification catalogues.
The project has identified a wide-ranging group of around 50 bottlenose dolphins. This small population size is a conservation concern - understanding their movements and monitoring their reproduction is vital for conservation management. Individuals from this population are being compared with other bottlenose dolphin observed off the east coast of Scotland, to establish whether east and west populations cross over. This research activity is being conducted in collaboration with the Cetacean Research and Rescue Unit (CRRU), who run another Earthwatch cetacean research project in the Moray Firth. The largest population surveyed is of minke whale, with 108 individuals so far identified. The minke whale catalogue is now at a point where comparison with other organisations will further increase our knowledge of minke distribution, population and movements. There has been a marked decline in minke whale sightings in recent years, and the change in abundance patterns of small schooling fish prey is evidently affecting the whales.
Results of surveys are shared with the local community, including those involved in the wildlife watching industry and the general public. One of the aims of this outreach is to encourage people to report sightings which can be added to the dataset. Sightings from this Community Sightings Network are shared with the Sea Watch Foundation, the national coordinator for UK sightings, who carry out 10 year reviews to produce a comprehensive summary of the status and distribution of UK cetaceans.
Embling, C.B., Gillibrand, P.A., Gordon, J.G., Shrimpton, J., Stevick, P.T. & Hammond, P.S. (2010) Using habitat models to identify suitable sites for marine protected areas for harbour porpoises (Phocoena phocoena). Biological Conservation, 143 (2): 267-279
Stevick, P.T., Incze, L.S., Kraus, S.D., Rosen, S., Wolff, N. & Baukus, A. (2008) Trophic relationships and oceanography on and around a small offshore bank. Marine Ecology Progress Series, 363: 15-28
Weir, C.R., MacLeod, C.D. & Calderan, S.V. (2009) Fine-scale habitat use by white-beaked and common dolphins in the Minch (Scotland, UK): evidence for interspecific competition or coexistence? Journal of the Marine Biological Association, 89 (5): 951-960