Comparative analysis of habitat use and ontogenetic habitat-shifts among coral reef damselfishes

Habitat characteristics play an important role in determining the structure of fish communities. The decline in fish diversity and abundance with the decline in coral diversity and cover may be explained by habitat specialisation and partitioning among reef fishes and/or preferences for particular corals that are susceptible to disturbance. These preferences may develop at different life history stages. Here, we investigated patterns of habitat specialisation and ontogenetic shifts in habitat preference among 14 co-existing damselfish species at Lizard Island lagoon on the Great Barrier Reef. Although live coral cover contributed only 26% of the substratum, 28% of adults and 57% of new settlers were mostly found on live coral, indicating a strong preference for live coral habitat by new settlers. Only a few species exhibited a high degree of habitat specialisation and low overlap in habitat use with other species. Specialisation differed among species and life stages. New settlers were more commonly associated with finely branched corymbose corals and using those habitats with higher frequency than expected based on habitat availability alone. Adults were more commonly linked to more open branching morphologies or non-coral substrata. Our results suggest that habitat loss may not uniformly impact on all life stages. While adult individuals may not be as reliant as juveniles on corals, detrimental effects of habitat loss on juvenile survival may have longer-term impacts on adult populations. As juveniles show preferential associations with particular coral species, such as corymbose corals, the loss of these growth forms is likely to have the most significant negative impacts on this critical life history stage.