I was surprised to learn that we signed an agreement in 1964 which allows some other countries to fish in our coastal waters (HERE). The countries are Ireland, Holland, Belgium, Germany and France. The London Fisheries Convention allows fishing between 6 and 12 miles from shore and it sits alongside the Common Fisheries Policy. In return we can fish in their coastal waters. The government now proposes to pull out of the agreement.
This started long before we joined the EU so I assume there was some benefit to us at the time and probably some ongoing benefit otherwise the fishing industry would have called for us to withdraw years ago. That or they didn't realise the agreement existed. According to the BBC the industry welcomes the move so I'm not sure they did know about it before they called for us to leave the EU.
The EU are apparently claiming the 1964 agreement was superseded by the Common Fisheries Policy and therefore makes no difference whether we withdraw from it or not (HERE). I think this sounds more palusible with Michael Gove, who made the announcement, doing it for effect more than anything else.
“UK denunciation of London Convention=no change: EU law/Common Fisheries Policy had superseded it. EU 27 interests=my priority for negs,” Mr Barnier the EU chief negotiator said in a post to his Twitter account.
Whatever the right and wrongs the practical effect will be close to zero. The environment department said an estimated 10,000 tonnes of fish worth an estimated £17m, was caught by vessels from other countries in 2015 under the London convention.
The overall UK fisheries sector with over 6,000 vessels landed 708,000 tonnes of fish worth £775m in 2015 so the convention's impact is almost nothing.