Before you run away to something that sounds more interesting and less niche than studying fish (there weren't a whole lot of scientific fields beginning with "i" that I could dig up) give me a moment to get to the invisibility.
The pirate perch, or Aphredoderus sayanus, has been found to be capable of making itself functionally invisible to its prey, probably through a chemical means know as chemical crypsis. The experiment demonstrating the fish's abilities went along these lines: Frogs and beetles that don't lay their eggs around predators they recognize were placed in the vicinity of pirate perch. Instead of not laying eggs and avoiding the perch as they normally would, they acted as though the fish were not present at all. Scientists aren't absolutely sure it's chemical crypsis pirate perch are using to disguise themselves, but if it is, they would be the only known species to camouflage themselves that way.
Have any favorite fish species (either to eat or to look at)? Do you or did you ever own any aquatic animals?
-----The Golden Eagle