Local boaters are urged to be respectful of dolphins

But there are concerns that local boat users might be flouting guidelines aimed at protecting the animals and islanders.

DolFin was set up in 2019 to understand the abundance and distribution of different cetaceans within Bailiwick waters.

During the project’s first full year there were 124 marine mammal sightings over 82 separate days. Five separate species were recorded – bottlenose dolphins, common dolphins, harbour porpoises, Risso’s dolphins and minke whales.

‘The greatest number of sightings was reported in July [31 sightings],’ said Ms Harris.

‘This is likely due to both more people being out near the water with good weather and marine species possibly also being in the area more frequently at the time. The majority of sightings were of bottlenose dolphins (58.4%) followed by common dolphins (15.2%) in 2020.’

The project team have been trying to determine population size by identifying dorsal fins, but this can be tricky because the animals are fast.

‘So far we have a catalogue of 16 confirmed unique individuals, many of which are repeat visitors to the island,’ said Ms Harris.

‘Newer techniques for population monitoring rely on listening in to dolphins using acoustic buoys, as dolphins have “signature whistles”, much like unique names for one another. This technology is currently out of our reach for the moment.’

Local guidelines are that people interact respectfully with dolphins.

‘The majority of people are sensible but without enforcement, I have myself seen some of these rules flouted,’ Ms Harris said.

‘The majority of boaters are very aware, but it only takes one big boat to really do some damage. I will always worry that some of the rules, particularly to not feed any cetaceans, and to not swim with them, might be broken and result in real human harm as well as risking the health of the animals.

‘These are wild animals and even if they’re just playing could really hurt you if you swim with them.’

Pilot whales have vanished from local waters, but dolphin sightings have become more common.

‘Currently, the most frequently sighted cetaceans in our waters are bottlenose dolphins, and they have been sighted in all months of the year,’ said Ms Harris.

‘One of the goals of the DolFin project is to work out why they’re coming here. This is why identifying individual dolphins is so useful – we can compare their fins to other areas such as Normandy and see if they’re a French dolphin, if they’ve travelled down from Wales or are from somewhere else.’

The English Channel is one of the noisiest stretches of water in the world, busy with marine traffic.

‘In comparison, our waters are relatively quiet,’ Ms Harris said.

‘Marine noise pollution affects whale and dolphins a lot – they can become lost, disorientated and even end up stranded and die. Marine noise masks their song and ability to communicate with each other.’

Ms Harris said they did not know if the animals were breeding here but they would be interested to find out. Young dolphins have been seen in local waters.

When it comes to the local environment for dolphins, Ms Harris said they formed a natural part of the ecosystem and they helped keep marine life in check.

n Islanders are asked to report any dolphin sightings, with the time, date and location, to Ms Harris at dolfinproject@outlook.com or the Guernsey Biological Records Centre.