MEPS 305:163-175 (2005)  -  doi:10.3354/meps305163

ABSTRACT: The nocturnally foraging cardinalfishes are known to exhibit a high degree of fidelity to their daytime resting sites. However, the microhabitats chosen as resting sites, the degree of specialisation on live coral substrata and the degree of overlap among apogonid species have not been described. These patterns potentially affect how declining coral availability will impact the diversity and abundance of apogonid assemblages. Here, microhabitat use, abundances and patterns of co-occurrence are examined for 10 common reef-dwelling apogonids in Kimbe Bay, Papua New Guinea. Nine of the 10 species were strongly associated with live scleractinian corals, with more than 80% of the individuals resting in branching forms. The exception was Apogon nigrofasciatus, a specialist on cave or crevice habitats. Among the available coral species, the vast majority of cardinalfishes were associated with a single coral species (Porites cylindrica), although the degree of specialisation varied among species. Apogon leptacanthus and Sphaeramia nematoptera were almost always only found on P. cylindrica, while Apogon bandanensis, Apogon compressus, Apogon fragilis, Archamia fucata, Archamia zosterophora, Cheilodipterus artus and C. quinquelineatus also used a range of other corals. There was a positive relationship between the range of substratum types used and the number of groups of each species observed. The 9 coral-dwelling apogonids exhibited a high degree of overlap in depth range and in the use of coral microhabitats. Over 75% of aggregations were made up of more than one fish species. The high level of both specialisation and overlap in habitat use suggests that the future biodiversity of cardinalfishes in Kimbe Bay could be linked to the fate of a single coral species.

KEY WORDS: Abundance · Aggregation · Apogonidae · Community structure · Coral reef · Habitat specialisation · Resource overlap · Resting site