Fish have brains, but theya re very primitive. I don't think they they have a much of a cerebrum, which is where most/all of thought takes place. They pretty much live on instinct- find food, avoid predators, and reproduce.
ADDITION: Not all living thing shave brains the way we do. There are seprate patrts of the brain, and the simplest vertebrates only have the more primitive parts. There are unicellular organisms that are living but have not brains, bacteria are alive but they have a nucleus to control everything. There are lots of differences between fish brains and human brains, like I said they mostly run on instinct. Some organisms have some sort of nervous system, and may have a group of cells that help control it, but it isn't nesessairly a "brain".
Make your own food decisions, but recognize that there may be grey areas on intelligence.