The once-prized inshore herring of the Zuyder or Zuider Zee disappeared when in 1932 the Dutch completed the construction of the Afsluitdijk, the dyke which now closes off the former bay from the North Sea.

After the 2nd World War there were sightings of refugees – or at least fish which closely resembled the Zuyderzee herring – in the Thames estuary, off the coast of Suffolk and as far north as Northumberland.

Behind the dyke land was reclaimed and the freshwater lake IJsselmeer was created. In Sweden and Finland there are freshwater herrings which adapted like char to Ice Age-related habitat changes. Modern construction timescales didn’t allow this. The Zuyderzee herring is extinct.