On the other hand it seems almost inexcusable that the UK isn't self sufficient for fish, we're surrounded by ducking water FFS.

Dear god, let's not bring up fishing again, it was exhausting enough for Brexit.

Fish do not obey national boundaries. They don't carry passports. The entire North Atlantic ecosystem needs to be considered as one, along with quotas for sustainability. I'm not sure if it's mathematically possible for all of Europe to hit this "recommended" consumption level from pelagic fish without quickly making them extinct, has anyone checked that?

Agreements about which waters who can fish, and it being cheaper to import from elsewhere.

Short-sighted I agree. It would be worth paying a bit more for security - the same applies to a lot of other things.