Project background

One area of Scotland that has been documented as a particular stronghold of white-beaked dolphins is the Minch, situated between Lewis and the west Scottish mainland.  In this region high densities of white-beaked dolphins were recorded during the 1980s and 1990s at latitudes of 58º–58º30'N (Weir et al., 2001; Reid et al., 2003).  However, a recent study reported an apparent decline in the occurrence and abundance of white-beaked dolphins in the Minch based on both long-term stranding records and sightings recorded from the Ullapool to Stornoway ferry since 2001 (Macleod et al., 2005).  It was suggested that this decline was primarily driven by local increases in water temperature, with the implication that this species may decline along the west coast as a result of future climate change (MacLeod et al., 2005).  A simultaneous increase in the occurrence of short-beaked common dolphins (Delphinus delphis) within the same region since 2001, has led to the suggestion that this warmer water species may be moving northwards into the Minch, resulting in potential competition with white-beaked dolphins (MacLeod et al., 2005, 2007).  The interaction between white-beaked and common dolphins, their current status and their relation to sea water temperature within the Minch remains unclear, and the purpose of this project was to collect dedicated preliminary survey data to clarify these issues.

Aims and objectives

The White-Beaked Dolphin Project aims to improve knowledge of the status and ecology of white-beaked dolphins within Scottish waters to aid their future conservation and management.  The 2007 field survey was conducted as a preliminary study into the occurrence of white-beaked dolphins in the Minch, intended to form a baseline for future fieldwork.  The main aims and objectives of the fieldwork were:

Aim 1

To establish to what extent white-beaked dolphins still inhabit the Minch, and whether their distribution and relative abundance remains similar to that reported in previous years (e.g. in Reid et al., 2003) or has changed significantly.  Simultaneous recording of water temperature and sightings of other cetacean species (particularly common dolphins) would allow consideration of reported declines in white-beaked dolphins related to increasing temperature and competition with other species. 

Aim 2

A secondary aim of the project was to collect baseline data (particularly via photo-identification, behavioural and acoustic work) on the ecology of white-beaked dolphins in the Minch, to further understanding of this poorly-studied species in Scottish waters and examine the potential for a future long-term at-sea study of this species.

Objectives

The key questions that the survey work aimed to address were:

	What is the current occurrence (distribution and relative abundance) of white-beaked dolphins in the Minch, and has this changed since the 1980/90s?
	Does white-beaked dolphin distribution in the Minch contrast with that of any other odontocete species?
	Are habitat variables such as water temperature or depth a crucial factor governing white-beaked dolphin distribution in the Minch?
	Is it feasible to establish a long-term study of white-beaked dolphins in the Minch based on photo-identification methodology?

References

MacLeod, C.D., Bannon, S.M., Pierce, G., Schweder, C., Learmonth, J.A., Reid,R.J. and Herman, J.S.  (2005).  Climate Change and the Cetacean Community of North-West Scotland.  Biological Conservation, 124: 477-483.

Reid, J.C., Evans, P.G.H. and Northridge, S.P. (2003).  Atlas of cetacean distribution in Northwest European waters.  Joint Nature Conservation Committee, Peterborough, UK.

Weir, C.R., Pollock, C., Cronin, C. and Taylor, S. (2001).  Cetaceans of the Atlantic Frontier, north and west of Scotland.  Continental Shelf Research, 21: 1047-1071.