An attempt to put tracking devices on three porpoises caught in the North Sea by Wageningen researchers has resulted in the death of one of the animals,

One of the porpoises was successfully fitted with a device and released but the second became too stressed and had to be returned to the sea without a tag. The third animal was left in the net and drowned. Porpoises, which belong to the whale family, can only stay under water for a limited amount of time.

The project, aimed at gaining an insight into the habitat and behaviour of porpoises, has been halted pending an investigation by Utrecht University’s veterinary department into the death of the animal and an evaluation by Wageningen University itself.

Porpoises (phocoena phocoena) are a protected species and that means the government must make sure the animals don’t come to harm when planning activities on the North Sea, such as offshore wind farms.

Dolphin protection organisation SOS Dolfijn said the death of the animal is “very worrying”. Director Annemarie van den Berg said it is one thing to tag the animals but it “must be done under the right circumstances,” she told local broadcaster NH Nieuws.