I suspect that the leaders of EU countries which have large fishing fleets are seriously worried/panicking (for their own jobs!) that the UK is going to drastically reduce/eliminate those fleets' access to the UK's rich fishing waters.
The EU knows how its rules and regulations pummeled the British fishing fleets, now it fears that it's their turn to experience the same collapse:
"I am not sure that an agreement will be reached between now and the end of the year," Mr Macron said at a meeting with fishermen in Paris on Saturday......Mr Macron also said fishing rights could be a sticking point in negotiations." https://www.bbc.co.uk/news/uk-politics-51601664