ok got my answer. going for monkfish to 99, and cooking to 99 with those.

I've heard people say that barbarian fishing is the fastest xp at something around 42k hour? Not sure but, they can't be cooked so your not getting much cooking xp from them. Fly fishing is supposed to be fastest after this at just a little less xp per hour than barbarian fishing and, if my calculations are correct getting 99 fishing this way will also provide you with enough fish to get 99 cooking aswell. Monkfish and shark are mainly for money but monkfish are decent xp and you could probably buy 99 cooking if you sold them.

monkfish.