Bangaii cardinals, Pterapogon kauderni, show a marked change in habitat preference as they get older, according to a paper just published in the journal Copeia.
The popular aquarium fish, which is said to be under threat in the wild due to over collection for the trade, shows an ontogenetic (age-related) shift in its habitat and microhabitat use. Young fish live in seagrass and around anemones, while adolescent individuals and adults are coral reef associated, and use corals and urchins as living substrates.
The shift is apparently not related to a change in diet or competition from conspecifics and the authors recorded overlaps in the habitat use of brooding males, pairs and young fish. However, they haven't been able to pinpoint the exact processes behind the segregation.
More information: Vagelli, AA (2004) - Ontogenetic shift in habitat preference by Pterapogon kauderni, a shallow water coral reef apogonid with direct development. Copeia, Vol. 2004, No. 2, pp. 364-369.