Sea shelf lures porpoises to Jersey's north-east coastline

  • ITV Channel's Hannah Ludlow went to find out why Jersey's north-east coast is so popular with porpoises

A sea shelf could be luring one of Jersey's most mysterious marine mammals to its north-east coastline during the winter months.

Between December and March, an influx of porpoises has been found to visit one particular area along the island's shoreline.

In 2016, Jersey's Marine Resources Department began placing underwater microphones called hydrophones in the sea surrounding the island.

The hydrophones are located around Jersey and its nearby islands. Credit: Government of Jersey Marine Department

Hydrophones contain SD cards which store data on the porpoise 'noises' they pick up. This is then downloaded and analysed by marine scientists.

There are 14 hydrophones surrounding Jersey and two are positioned to the north and south of St Catherine's Breakwater, just over a kilometre apart.

This year, the northern hydrophone La Coupe has had more than 3000 porpoise encounters, whilst the southern hydrophone Fara recorded just 200.

The inside of a hydrophone. Credit: ITV Channel

The Marine Resources Department are researching to find out why so many porpoises are gathering at La Coupe, but hardly any are swimming just one kilometre to the south.

Their working theory is that the mammals are following their prey, such as squid or baitfish.

Dr Peter Evans, porpoise expert and director of the Sea Watch Foundation, has a similar theory.

He says that the porpoise's prey is often found in a sea bank, or channel, like the one to the north of St Catherine's Breakwater.

Contour lines show how a deep area adjacent to the Breakwater suddenly becomes shallow, causing a shelf or basin.

Dr Evans explains: "Just north of the pier it becomes really deep, and then it becomes shallow again, creating a bank offshore.

"So I think the porpoises are using that channel to take fish, because that would be a good spot for fish."

Porpoises are difficult to spot off Jersey's coast, and many avid wildlife photographers have spent years trying to get the perfect shot.

Wildlife photographer, John Ovenden, says: "I've been looking at dolphins and wildlife since 1992 and I've only seen them a handful of times from the boat.

"If you do see them it's only a very quick glimpse. It seems to have a quick look and then it's gone and you never see it again."

Although porpoises begin to migrate from Jersey's waters at the end of March, research into their habits and behaviour continues all year round.

Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know…