Fish have brains. According to LiveScience, in 2013, scientists were able to successfully produce images of the activity of a fish's brain as it watched its prey.
Scientists have observed the neural signals of a fish as it watched its prey to understand how fish view the outside world. They looked at neuronal activity using a fluorescent marker. Scientists observed a fish's neuronal activity as it watched a dot on a screen and as it tracked a paramecium. The scientists were able to experiment on zebrafish, which have translucent heads; scientists developed a protein called GCaMP7a that lights up when neurons fire.