A multi-scale study of the relationships between habitat use and the distribution and abundance patterns of three coral reef angelfishes (Pomacanthidae)

The degree to which species partition resources often depends on the spatia l scale of the study. To investigate this, we examined the distribution and abundance patterns of 3 relatively rare pygmy angelfishes (family Pomacant hidae: Centropyge) among reef locations, depths and microhabitats at Lizard Island on the Great Barrier Reef. A strong association among species and b etween species and their habitat was found at some scales, but not others. On a broad scale, the abundances of the 3 species were highest at the same 4 sites (kilometres apart). These sites were all located at headlands, sugg esting that the patterns of abundance may be in response to the topographic features of the island at this scale. Differences among species occurred a t intermediate scales (10s to 100s of metres), where species were associate d with different depth zones or reef locations. Centropyge vroliki occurred shallower than C, bicolor, while the depth distribution of C, bispinosa ov erlapped with both of these species. Laterally along the fringing reef, C, vroliki were more abundant in areas where both C, bicolor and C. bispinosa were also abundant, but these 2 latter species were not correlated with eac h other. The proportions of substratum types present in home patches differ ed among species, to some extent reflecting the benthic composition of the reef area where each occurred. However on a fine scale (metres), all 3 spec ies appeared to use the same substratum type, which consisted of dead branc hing coral covered in algae, and occasionally formed multi-species groups. Species abundances were not correlated with this commonly used microhabitat , but rather the availability of the substrata characterizing the reef area s in which they were most abundant. Here, although Centropyge species use t he same type of microhabitat, they may be an example of species that partit ion space on the basis of non-preferred resources. For example, all 3 speci es used home patches containing high proportions of overgrown corals; howev er where this habitat was not available, C. bicolor used sand and rubble ha bitat at the reef base, while C, vroliki used coral habitat on the reef cre st. Most importantly, this study emphasizes that a multi-scale approach is necessary to determine appropriate scales for examining species association s and resource partitioning in reef fishes.