ANALYSIS OF MICROHABITAT STRUCTURE OF CORAL REEF FISHES RELATED TO GEOMORPHOROGICAL FEATURES

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Field observations were conducted to analyze microhabitat use by damselfishes on a shallow coral moat (<3m, about 6ha) of Shiraho reef, Ishigaki Island, Okinawa, using digitalized aerial photographs processed with image analysis software as field maps. The color same as the benthic landscapes that were identical to exact microhabitats of a damselfish (anemonefish) were extracted from the photographs, which were recognized as the potential habitats of the fish. Geometrical features of the potential habitats were analyzed on a computer related to population density data of the fish. Similarly, all benthic landscapes used by damselfishes were extracted from the photographs, and features of their microhabitats with higher species richness and diversity of all damselfish species in study sites were analyzed.The potential habitats for the anemonefish were 3 dimensional reefs that could be recognized on the aerial photographs, and population density of the fish in a quadrat was correlated with total aria and total perimeter of the potential habitats in the quadrat. This suggests that the anemonefish are abundant in a place where 3 D reefs are aggregated. Damselfish species richness and abundance in a quadrat were also correlated to the total area of 3 D reefs in the quadrat. Total area of aggregated 3 D reefs that can be recognized on aerial photographs may be an effective indicator of high species richness and abundance in a shallow coral reef moat.