I asked this question if the guys on my other forum, and got really interesting answers from some serious anglers and commercial guys.
A few are caught, but very few. Even on boats.
I asked the question because I had heard the odd tale, but never seen or caught myself, despite the fact I fish places like Filey Brigg a fair bit, which one would think would be about as perfect as it gets. Heard of just one caught there, and one caught in Scarborough harbour, both a while back, and both on the smaller side.
It seems the answer boiled down to the fact they preferred warmer waters, so stick almost exclusively to the Gulf Stream. North East waters are the coldest, and take longest to warm, of any round the UK. Colder even than the northern tip of Scotland.
That said, a few decades ago, when there was a very seriously cold stretch, many dead ones were washed up on beaches. Hazarding a guess, I would think they were swept into out waters by strong warm currents, then died when here (rather than being resident stock).
Hope that answers your question.