I have nothing at all against catching fish for food, but to cath one, weigh it, and throw it back, is nothing short of cruelty. Sport is two or more equal contestants taking part willingly.
I judged a fishing contest for my workmates last summer, and every so often, a fish would be 'Foul Hooked', thats where the hook goes into the side of the fish, the fish then has to be pulled, bleeding and in pain, to the side, where the hook can be removed, the fish, still wounded, is then thrown back in, to be caught again.
Believe me. it might be fun for the Angler, but not for the fish.