Well, cephalopods have very different brain structures from fish. When dealing with animals, I personally err on the side of caution about limiting their mental potential since many creatures have much more going on in their brains than they have previously (or presently) been given credit for. Fish have a pretty simple brain in comparison to many other creatures. You might be surprised at how much research has actually been done on the fish brain and fish behaviors. They are a more readily study-able organism than many. I have to day that overall, I agree that fish do not show any human-relatable emotions. They do show behaviors and reactions to their environment, but they do not have a part of the brain where higher emotions are processed. That said, I generally still refer to a healthy, active fish as "happy" because it is the easiest thing to say in the situation.
