Brexit and Puffins?

The Puffin (Fratercula artica) is, perhaps, the UK's most appreciated seabird. Puffins largely feed on tiny sand-eels from the seas around UK coasts. There's ample historical evidence, that Puffin numbers decline, when sand-eel stocks are decimated by overfishing. Laws have, consequently, been brought in banning the mass removal of sand-eels from parts of North Sea waters. Denmark has been most impacted. It generally catches 250,000 tonnes of sand-eels each year. That catch is processed to produce fish oil and animal feed. The animal feed is given to commercially-important (for Denmark), pigs and farmed salmon. Other countries (including the UK) have converted sand-eels into agricultural fertilizer. The EU claim the UK's fishing ban, contravenes its post-Brexit deal and must be lifted (https://www.bbc.co.uk/news/articles/ce9rrpn955qo). Puffins, of course, don't get to vote on whether the ban should be removed or not. I thought the EU favoured maintaining/improving biodiversity?