Photo-identification is a simple, powerful, non-invasive technique aiding the study of bottlenose dolphins in Cardigan Bay.
In the early 1970s, scientist found out that it was possible to recognise individual whales and dolphins from good quality photographs. From pictures, killer whales are usually recognised by their dorsal fins and saddle patches, sperm whales by irregularities in the edge of their flukes, humpback whales by the black and white pattern underneath their flukes and blue whales by the mottled patterns of their bodies. The Cardigan Bay bottlenose dolphins are recognised by their dorsal fins.
Photo-identification of bottlenose dolphins
All bottlenose dolphins are different and individuals can be recognised by the markings on their dorsal fins. These markings can be nicks or notches to the fin, natural blemishes on the animal’s skin, or scars and rake marks from the teeth of other dolphins. If photographed sufficiently well then individual dolphins can be identified. The perfect bottlenose dolphin photo-identification image is of the dorsal fin at close range in sufficient light. Ideally, photographs are taken of the left and right sides of the dorsal fin so there are two photos per animal as this will help with future identification. Each new dolphin is assigned an identification (ID) number and/or name. The images are then sorted according to the number of nicks on the dorsal fin and their ID numbers and a catalogue of individual dolphins is compiled to allow future identification of the individuals.
How does photo-identification help with CBMWC’s bottlenose dolphin research?
On our survey boat trips photos are taken of the dolphins encountered. Each new set of photos are matched to those in the existing catalogue to work out which individuals were seen on a particular trip and at what locations. Any new individuals (those not found in the existing catalogue) can also be identified at this stage. This matching process is very important as it allows us to estimate the bottlenose dolphin population within the Cardigan Bay Special Area of Conservation (SAC) and allows for any changes in the population to be monitored and reasons for any changes investigated. Movements and migration patterns of the dolphins can also be studied along with life histories, as mothers and their calves can also be identified and the calves tracked as they grow.
What have we found?
Photo-identification of bottlenose dolphins was first conducted in Cardigan Bay in the 1980s and repeated in the early 1990s and in 2001. In 2005 we established our annual Photo Identification Catalogue, in cooperation with other Welsh marine organisations. In 2005 139 individual dolphins were photographed and identified from our survey trips. We have now identified over 250 individuals.
We are keen to discover how many of the same individuals revisit Cardigan Bay each year and whether there is a significant change in which animals visit the Bay at different times of the year.
Please note that this is a low resolution version of the catalogue ideal for looking at on screen. The resolution is too low for quality printing and images may become distorted or pixilated should you try printing this document. If you require a higher resolution version then please contact the Cardigan Bay Marine Wildlife Centre.