Abstract
Habitat specificity plays a pivotal role in forming community patterns in coral reef fishes, yet considerable uncertainty remains as to the extent of this selectivity, particularly among newly settled recruits. Here we quantified habitat specificity of juvenile coral reef fish at three ecological levels; algal meadows vs. coral reefs, live vs. dead coral and among different coral morphologies. In total, 6979 individuals from 11 families and 56 species were censused along Ningaloo Reef, Western Australia. Juvenile fishes exhibited divergence in habitat use and specialization among species and at all study scales. Despite the close proximity of coral reef and algal meadows (10's of metres) 25 species were unique to coral reef habitats, and seven to algal meadows. Of the seven unique to algal meadows, several species are known to occupy coral reef habitat as adults, suggesting possible ontogenetic shifts in habitat use. Selectivity between live and dead coral was found to be species-specific. In particular, juvenile scarids were found predominantly on the skeletons of dead coral whereas many damsel and butterfly fishes were closely associated with live coral habitat. Among the coral dependent species, coral morphology played a key role in juvenile distribution. Corymbose corals supported a disproportionate number of coral species and individuals relative to their availability, whereas less complex shapes (i.e. massive & encrusting) were rarely used by juvenile fish. Habitat specialisation by juvenile species of ecological and fisheries importance, for a variety of habitat types, argues strongly for the careful conservation and management of multiple habitat types within marine parks, and indicates that the current emphasis on planning conservation using representative habitat areas is warranted. Furthermore, the close association of many juvenile fish with corals susceptible to climate change related disturbances suggests that identifying and protecting reefs resilient to this should be a conservation priority.
Highlights
Settlement of fish from the pelagic environment and the subsequent recruitment into benthic populations are key processes in determining the structure of fish communities
Whilst considerable debate has centered on the relative importance of density dependant and independent factors in structuring adult communities [1,2,3], it seems the availability of suitable habitat plays a key role for most species at some spatial scale [4,5,6]
To assess if juvenile fish preferentially associate with live coral, dead coral or coral structure more generally we examined all transects where a species occurred and calculated the percentage of groups occurring in live or dead corals, along with the sum of these percentages
Summary
Settlement of fish from the pelagic environment and the subsequent recruitment into benthic populations are key processes in determining the structure of fish communities. We examine habitat preferences of both ecological and fisheries important juvenile fish, determining if each species is associated with live coral, coral skeletons and different coral growth forms. We assess the probability of observing juvenile fish in algal meadows, which are a prominent feature of coastal systems along the tropical coast of Western Australia, often occurring in close proximity to coral reefs [34]. This information will; improve our ability to predict effects of coral loss on reef fish assemblages, identify the potential importance of nursery habitats and advance our capacity to manage reef fish communities
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