When I was 16, I was lucky enough to be invited by my godmother to stay in a holiday house her parents had on a loch open to the sea on the West Coast of Scotland. While there, we took a motor launch out, trolling for fish (that is, towing a lure across the loch). We were catching fish called pollack, and they were huge, some over 20lb. At the end of the day, we left a full fish box of pollack on the quayside, and the villagers helped themselves, stocking up their freezers with winter coming.
I went back to the cottage about 10 year ago, and did some spinning off the rocks, catching a small pollack little bigger than the lure I was using. I spoke to a local about the poor fishing, and he told me that some years before, a Spanish factory ship had come into the loch and netted everything, scouring the bottom and leaving with fish of every size. There was nothing left to grow on. The local said that in the summer, he used to fish for an hour after work in the summer, to catch enough herring for his family for supper. Now there were no herring left.
We need to take back control of fishing in our waters and carry out commercial fishing sustainably. The EU shows no inclination to do so. The trade deal after the transition must give us back full rights to our fishing grounds.