The three big seal rescue centres along the Dutch coast have dealt with 35 seals this year, which have become entangled in fishing nets or other litter, the Volkskrant reported on Tuesday.

In an average year, the centres help some 40 seals in total.

The problem is particularly an issue for young seals who “grow” into whatever they have become caught up in.  “It does not expand with them and that leads to fatal trauma to the airways and blood vessels,” said Emmy Venema, from the Pieterburen seal centre. “It is a very slow, painful death.”

More seals are being hurt by waste because the Dutch seal population is increasing. The number of grey seals in the Wadden Sea has risen 12% over the past five years to around 10,500. They share the sandbanks with over 22,600 ordinary seals, according to researchers at Wageningen University.