Alot of people will tell you that here as well.. imho it's not a question IF animals are capable of being "Happy" but if we can understand they do not think as we do.. so being "happy" is a subjective observation. Sticking to fish, my predetory fish in particular exhibit behavior of enjoyment or happyness. They play, and otherwise show similar behaviors I've seen in other animals that would suggest happyness. so do I think tehy are Happy? Yep. will someones telling me that they can't be happy change my mind? Nope. Am I personificating them? I don't think so since I don't directly corelate their behavior towards Human, but base it off what I understand of the animal kingdom in general. imho it's only a matter of time before science catches up.

joking aside i see some eally good replys and its early yet,
There are some pseudo scientists that will say otherwise, but pseudo science is not science.