Monday 18 January 2021

Dutch porpoise population rises seven-fold in 30 years

A Harbour porpoise. Photo: Erik Christensen via Wikimedia Commons

The porpoise population in the Dutch part of the North Sea has increased seven fold since 1991, according to research by national statistics agency CBS and Wageningen University.

One reason for the increase has been the general movement of porpoise populations from northern parts of the North Sea towards the south, the researchers said.

‘Porpoises were abundant in the Netherlands till they disappeared mid 20th century but returned in the late 1980s and early 1990s,’ Steven Geelhoed from Wageningen Marine Research told

‘The total North Sea population has remained at the same level since 1994 so porpoises shifted from the northern North Sea to the heavily used southern part of the North Sea. The reasons are unclear, but a link with food availability seems logical although we can’t quantify this.’

To count porpoise, the team use a plane along predesigned transect lines to cover the entire Dutch North Sea. ‘We only fly with good weather but off course you miss animals that are submerged,’ Geelhoed said.The team use data from tagged animals and other techniques to try to compensate for the animals that are missed.


As the number of porpoise rise in the Dutch part of the North Sea the number of strandings had gone up considerably, with 980 recorded in 2012, although this had fallen to 320 by last year.

Causes of death established in stranded porpoise include drowning in fish nets, infections, starvation and collisions with ships’ propellers.

The porpoise was removed from the list of most threatened Dutch species earlier this month.

Thank you for donating to

The team would like to thank all the generous readers who have made a donation in recent weeks. Your financial support has helped us to expand our coverage of the coronavirus crisis into the evenings and weekends and make sure you are kept up to date with the latest developments. has been free for 14 years, but without the financial backing of our readers, we would not be able to provide you with fair and accurate news and features about all things Dutch. Your contributions make this possible.

If you have not yet made a donation, but would like to, you can do so via Ideal, credit card or Paypal.