SMRU Consulting and the University of St Andrews

Improving understanding of bottlenose dolphin movements along the east coast of Scotland

The bottlenose dolphin is a European Protected Species and an important predator in Scottish coastal waters. The Scottish east coast bottlenose dolphin population has been studied since 1989 based on the ability to identify individual animals from photographs of the scratches, nicks and notches on their dorsal fins. This work led to the designation of an SAC in the Moray Firth but also demonstrated that during the 1990s, the population expanded its range to the south as far as the Tay Estuary, St Andrews Bay and the Firth of Forth.

However, the extent to which dolphins between the northern and southern parts of their range remains poorly understood. Better knowledge of this would be valuable to inform assessments of the impact of proposed offshore energy developments in the area.

To understand the potential impacts of offshore windfarms on these dolphins, we need the best information possible on how they use this area, including their movements up and down the coast. Bottlenose dolphins can be identified individually from photographs of natural markings on their dorsal fins, a method known as “photo-id”.

To improve the understanding of bottlenose dolphin ranging patterns along the east coast of Scotland, SMRU Consulting has teamed up with Prof Philip Hammond from the Sea Mammal Research Unit (SMRU) of the University of St. Andrews to intensify sampling in the Tay Estuary and adjacent areas over a three year period. The resulting data will be integrated with data from intensive sampling in the Moray Firth through ongoing collaboration with Prof Paul Thompson from the University of Aberdeen (AU) Lighthouse Field Station in Cromarty.

Photo-identification data is being collected between May and September during 2017, 2018 and 2019. Sampling comprises a total of 20 one-day trips in the southern part of the population’s range, spread over the season so that movements can be captured at the finest scale possible. In the laboratory, the photographs are graded for quality and images of dolphins from the best pictures are matched to the existing catalogue of individuals identified in previous years. This enables increased knowledge of the lives of known animals and to document any new ones seen for the first time.

Improving understanding of the north-south movements of the Scottish east coast bottlenose dolphins relies on matching photographs of individuals seen at different times in different places, hence the need for intensive sampling and for collaboration with colleagues working in the Moray Firth. When added to existing data, the new data generated over the three years of this project will enable questions to be answered about the rates of dolphin movements up and down the coast and whether there may be differences in movements between males and females, or among animals of different ages.

Studies of this dolphin population were initiated by the Universities of Aberdeen and St Andrews more than 25 years ago in the Moray Firth and extended to the Tay and Forth Estuaries in the 2000s. Despite this history, there are still important gaps in our knowledge. Bottlenose dolphins can live for many decades; the oldest known-age animal is a 62-year-old female in Sarasota Bay, Florida. Long-term studies are therefore needed to build up enough knowledge about the population to inform decisions about human activities, such as at-sea energy developments, that may affect it.

Many of the dolphins that will be photographed over the three year monitoring period will have been seen multiple times over many years and will therefore give information on their life history, for example, when mature females had calves. This knowledge can be used to inform the projects studies and to interpret results, including updating estimates of population size, and mortality and birth rates. At the end of this project, improved understanding of the movements and population biology of bottlenose dolphins should help in assessing the impact of future wind energy developments off the east coast of Scotland.

Prof Philip Hammond, Principal Investigator and academic lead of project, Sea Mammal Research Unit (SMRU), University of St Andrews, said: “
“This project gives us the opportunity to collect sufficient photo-id data over the next three years to greatly improve our knowledge of the movements, natural mortality rates, birth rates and size of this protected population of dolphins. In turn, this information will provide the best possible basis for assessing any impacts of offshore windfarm developments.

“Our existing knowledge of the lives of these animals provides essential background to the new study, which we expect to result in a significant step forward in our understanding of bottlenose dolphin population biology. Our aim is that this detailed case study will also serve as a model for other dolphin populations in other areas.”

Dr Carol Sparling, Technical Director, SMRU Consulting, said: “It is incredibly important to have a good understanding of the population dynamics and behaviour of wildlife populations to predict and understand the potential effects of any industrial activity in the sea. Impact assessments for projects such as offshore wind farm developments and harbour construction often have to be done without good information on the baseline conditions for the populations potentially being impacted. This project will provide extremely valuable baseline information.”

Last updated: 2017-06-20 13:17