Let me first clarify that there is no "crownfish" in the real world, to the best of my knowledge.

The crownfish is named for its prominent crown, which distinguishes it from other equally brightly-coloured tropical fish. Its hot pink stripes are, however, signature, and rarely found in other species of fish. Such features allow for them to find partners to mate, which is of utmost importance for a dwindling species.
Crownfish generally cluster near the bubble coral plant, preferring to stay away from the fray of bustling fish instead of mingling. Yet this has not always been the case. Some librarian villagers hold books that detail feasts of crownfish, dated centuries back when villages were still ruled by a tyrant king. It has been hypothesised by Steve that the excessive fishing of crownfish have killed all that venture from their homes, driving the rest into the reefs. This theory has yet to be proven as Steve is reluctant to experiment on the endangered species, much less taste it to test whether those feasts were real.

The story is lacking in terms of the logic, but honestly I just wanted to make a hot pink Nemo :)