A real favorite spot for me to go fishing and then have my catch cooked for me is Travellers Rest at the mouth of the Negril River down at the bridge to the left of the Craft Market.
The catch in the picture above was about two hours worth of fishing just off the cliffs inside the reef area.
I would pay $5000 J for both the fishing and the cooking (I guess that is about $75 at that exchange rate. I last went out during my 2006 visit. You can go there the late afternoon before the day you want to fish and strike up a deal.
Peace and Guidance.