A wildlife expert has raised concerns over a sudden decline in porpoise sightings along the north Wales coast.

Mick Green, manager of the Bardsey Marine Mammal Project (BMMP), which monitors marine life around Bardsey Island, Gwynedd, suspects that fishing activities, particularly the use of nets, could be a major factor in the drop. The project’s latest survey, which used drones for the first time, recorded a 10% decrease in porpoise sightings per hour.

Since 1999, BMMP has been studying whales, dolphins, and porpoises along Wales’ north-west coast. Traditionally, boats were used for data collection, but they are time-consuming to launch and their motor noise can disturb marine life. The latest survey, however, utilised drones to take photographs and record porpoise sightings from fixed clifftop locations, providing a less intrusive monitoring method.

Bardsey Island’s waters are a designated Special Area of Conservation, known for their strong currents, which typically attract pods of porpoises. However, last year’s survey revealed a decline in hourly sightings, leaving Mr. Green “very worried.”

He said: “It seems to be a wide-spread decline.

“I know other projects on the east coast of Ireland have seen declines there, as have our colleagues on Anglesey.

“It is something various organisations are working on, and we need to start looking at this.”

He believes fishing nets may be contributing to the decline and seeks to determine whether the porpoises have moved or if their numbers are truly decreasing.

“We don’t have a big fisheries industry here in Wales, but certainly, in the more ocean waters, more are caught up in the nets,” he added.

To gain a clearer understanding, BMMP plans to recruit additional observers on Pen Llŷn to complement those already stationed on Bardsey Island. The goal is to assess food availability, disturbances, and potential threats affecting porpoises. Mr. Green hopes that the findings will prompt the Welsh government to take action to address the issue.

However, not all experts have observed a decline. Nadia Tomsa, manager of Sea Trust Wales, runs the Harbour Porpoise Photo ID Project in Pembrokeshire. Since 2018, a team of volunteers has conducted up to four land-based surveys per week at key locations, such as Strumble Head and Ramsey Sound.

Using pigmentation patterns, scars, and fin notches, the team has cataloged over 200 individual porpoises. Ms. Tomsa reports that volunteers regularly observe large groups of resident porpoises in Pembrokeshire and has not noticed a decline in sightings.

“Perhaps something else is going on up in north Wales,” she added.

However, she acknowledges that because her project tracks only resident porpoises, the data may not fully reflect the species’ overall population trends along the Welsh coast.

Despite the conflicting observations, Ms. Tomsa emphasises the need for stricter marine conservation measures to safeguard porpoises across Welsh waters.

“Porpoises are at risk as they are so small and they do need more protection,” she added.

As concerns grow, conservationists continue to push for greater protections to ensure the long-term survival of these marine mammals.