The solution's very simple.
Just.don't.eat.fish.at.all
I wouldn't want the agony of being lassooed, dragged under water and drowned by a giant sea monster, so I extend the same courtesy to fish who face the reverse situation (who are likewise sentient and have just as much interest in continuing and enjoying their existence as humans, albeit in their own fishy way). It's just an example of the age old golden rule, one should treat others as one would like others to treat oneself. As it is scientifically proven fish feel pain and suffering, and I seek to avoid my own pain and suffering, therefore I shouldn't inflict it on others (or pay others to do this on my behalf).
It doesn't matter that fish aren't as cute/intelligent as some land animals; it would be morally wrong to suggest that is more acceptable to torture an unattractive human than a cute one, would it not? The only morally relevant criteria here is sentience.
There's no reason to eat fish at all, we can meet all our nutrtional needs with a plant based diet. Protein is abundant as long as you're eating sufficient calories; B12 is found in marmite type spreads, fortified plant milks and supplements; omega 3's are found in walnuts and flax and eating a diet low in refined/ processed fats. It's not nutritionally necessary.
Just because it feels pleasurable to the taste buds doesn't make it right. Torturing kittens may feel awesome to the perpetrator, who invokes the hedonisic argument, "well, it feels good to me, therefore there's nothing wrong with it". Most people would agree that idea holds no weight and is repugnant.
Therefore, if it's not nutritionally necessary to eat fish or land animals, doesn't the same argument hold?