I catch fish with my Longship. Parked it outside of a small outpost where there were a lot of fishing jumping and every time I went out to it I just was able to scoop a few fish off the deck. I got 90 raw fish meat over the couple of (in-game) days that I had the boat there.

I did not enjoy the actual fishing skill, so it's nice I can catch fish using my longship as a net.

As for how fishing could be improved, I agree with the OP. Simply changing it so that skill is gained by actually CATCHING fish would go a long way to making it better.

Also they should change the way stamina drain works when fishing. Rather than the current system "if you don't have high skill you simply cannot cast far without running out of stamina", it would maybe be more fun if it was a bit of a mini-game, such that you had to time when you reeled vs. let the line play, and you lose stamina only if you don't time it right.