There is a boat called missy moo that runs fishing trips from bangor.
The skipper has a good reputation.
My mate from work was out on his boat on Tuesday 27th evening, and caught loads of mackerel, As well as other fish.
You will have to book a place on the boat early, Because his boat is popular and fills up quickly, phone him at least a few days before you intend to go out with him.
http://www.missy-moo.co.uk