Study highlights the vulnerability of England’s South Coast bottlenose dolphin population.

A new study has used sightings data collected across England’s South Coast to reveal the vulnerability of our local bottlenose dolphin population. Led by researchers from the University of
Plymouth and implementing data collected by Sussex Dolphin Project, it is the first research to highlight the serious threat of human activity on coastal bottlenose dolphins between North Cornwall and East Sussex.

By studying over 7500 sightings reports from citizen science projects, researchers were able to create a detailed picture of these dolphin’s lives, including their social structures and movement across the South Coast. Whilst 326 dolphins were identified, it was found that just 48 individuals
were resident to the Southern coastline.

Unfortunately, preferred habitats for these magnificent animals significantly overlapped areas with high levels of human activity, such as fishing and vessel activity, and other pressures from marine traffic and recreational water use. High-risk areas included the Cornish coast, Plymouth Sound, Poole Bay, the Solent, and the Sussex coastline. These busy, urbanised areas not only raise a greater risk of injury to dolphins such as from boat strikes, but researchers found that dolphins frequently visiting these coastal waters are crucially exposed to high levels of pollution – an issue known to be detrimental to the health of whales and dolphins globally.

The study further highlighted that prey depletion, lack of available fish to consume, was identified as a significant risk to the future of this bottlenose dolphin population. This is particularly worrisome, as the Channel is already classified as one of the most heavily impacted marine ecosystems worldwide, with overfishing driving a decline in biodiversity in the area. With only 48 individuals in this pod, a much lower number than other coastal populations around Britain and Ireland, lack of prey would ultimately lead to an increased risk of this population’s extinction. The loss of even a single dolphin, particularly a female, would drastically decrease the population’s chances of survival.

Due to the wide-ranging activity of the South Coast’s bottlenose dolphins, with some found to travel over 750km between sightings, there is a substantial challenge in establishing effective protection, particularly as the English Channel is one of the busiest shipping lanes in the world.

Researchers suggested that flexible tracking of the dolphins alongside management of nearby human activity could hold the key to effective protection for this vulnerable population. Sightings data from local boat users, tour operators, coastal observers, and citizen science projects proved a highly valuable resource, and should continue so that we can learn more about the dolphin’s movements and behaviour to provide adequate protection in the future.

Citizen science data already plays an important role in the current understanding of bottlenose dolphins around the UK. Whilst the South Coast’s bottlenose dolphin population has been studied since the 1990’s, previous research was limited due to lack of data. In 2016, the South West Bottlenose Dolphin Consortium was formed, creating a shared dataset of historical and current bottlenose dolphin encounters across the South West. In 2019 this dataset was further extended across the whole English Channel coast of the UK, yielding almost 7500 sighting
reports between 2000 and 2020.

Cetaceans (dolphins and whales) can be difficult to study due to the rarity of encounters and their time spent underwater, but they can be identified from clear photos of just their dorsal fin. Much like a human fingerprint, a dorsal fin has permanent nicks, scratches, and scars unique to the individual. By building a catalogue of dorsal fin images from the sightings data alongside the location they were seen, researchers are not only able to recognise individual dolphins, but pinpoint which animals travelled together and identify which are residents, spending most of their time in our coastal waters.

This new research has emphasised the importance of sightings data collected from citizen science projects as a useful tool in the management and protection of these incredible, yet elusive, marine mammals. Perhaps more crucially however, it has highlighted that this small, coastal population of bottlenose dolphins is under enormous threat from the impacts of human activity across the South Coast of England. Without adequate protection for both the population and the areas in which they thrive, they are at great risk of disappearing from our local waters.