My gran put me off fish when I was very little. She used to do white fish or yellow smoked fish, filled with tiny tiny bones, in the oven with milk, and we'd get it on our plates, with what felt like a pint of fishy milk. It was vile. For many years the only fish I would eat was fishfingers (ideally in a sandwich, with HP Sauce) or tinned tuna mixed with a lot of Salad Cream. And after those many years, I became vegetarian.
I tried the cat with white fish a while ago. He wouldn't eat it, but he does like prawns and tuna.