North Sea in September, sole up and plaice under question

The North Sea in September hands Dutch kitchens their best flatfish of the year, and this autumn the numbers behind the plate pull in two directions: sole is up, plaice is in dispute.

Brown shrimp, plaice and Dover sole made up most of the volume landed by the Dutch cutter fleet in 2024, and those three still decide what a kitchen can actually buy between now and Christmas.

What the North Sea in September is giving

Ask for the meat percentage, not the price; the rest follows from it.

ICES raised its 2026 catch advice for North Sea sole by 16.4%, to 12,454 tonnes, and projects a spawning stock of 56,850 tonnes for 2027, about 7% above this year. The council put most of the improvement down to heavier fish at age rather than to more fish.

Plaice is the argument. The North Sea Advisory Council told ICES on 2 September that skippers are reporting catch rates well below what the estimated spawning biomass implies, and asked for the next benchmark to look again at discard survival, growth rates and size-at-age. Dutch auctions show the same split in price: sole has firmed across the grades while small and medium plaice has slipped.

Zeeland mussels are the other September marker. The 2025-26 season closed on 30 April with about 270,000 mosselton, 34% up on a 2024-25 season wrecked by die-offs on the Oosterschelde beds. Turnover rose 17% to €41 million. Oosterschelde mussels averaged 193 to the sample at 31.1% meat and fetched €177 a mosselton; Wadden Sea mussels ran smaller, 231 to the sample, at €119.

How to buy it

Meat percentage is the number worth asking for. Above 30% a mussel takes heat without shrinking to a button; below 25% no amount of white wine rescues it. The same logic runs through the flatfish: a September sole has fed all summer and carries fat a March fish does not.

The useful habit is not memorising a calendar but asking what came in that morning. A kitchen that buys properly has an answer, and it usually has a boat name attached to it.

Oysters run from now to April on the old R-month rule, and game and roots take the menus from late October, about when the Alba white truffle fair opens on 10 October. Until then the coast holds the better hand.