Fish stocks in the Wadden Sea area off the Friesland and Groningen coast have plunged over the past 50 years, according to the Dutch sea research institute NIOZ.

The volume of catch at a special research site near Texel has fallen from 65 kilos a day in 1965 to just five kilos a day in 2014.

The number of different types of fish being caught has also reduced. Salmon and skate have disappeared completely, and while in 1965 scientists would catch 24 eels a day, they now catch one every 10 days.

Reasons

‘What fishermen now say is a good catch would have been described as extremely poor in 1965,’ researcher Wouter van der Heij told broadcaster Nos.

The cause of the decline is unclear but sand movements between the Wadden Sea and North Sea, over-fishing, climate change and the closure of the IJsselmeer lake are all likely to be to blame.

The NIOZ has now set a second fish trap near Terschelling to step up the monitoring and plans to place a third in the eastern part of the Wadden Sea this year.