Specific composition and trophic organization of fish assemblages across Yonge reef, northern Great Barrier reef, Australia: A 1990 snapshot.

A standard visual census of fishes was carried out on Yonge Reef, a ribbon-shaped outer-shelf edge reef, in the Great Barrier Reef, Australia, in 1990. A total of 325 fish species were recorded from 30 censuses spanning all the 9 major habitats distinguished from the outer slope to back reef and lagoonal patch reefs, based on physiographical zones and coral communities. Hierarchical clustering classification and non-metric multidimensional scaling analyses, performed on abundance data, individualised five fish assemblages across Yonge Reef, themselves organized into three main geomorphological zones: (1) slopes, split into shallow and deep parts on both outer and lagoon sides of the reef; (2) reef front including the outer reef flat and the boulder zone; and (3) inner reef flat including from reef front to lagoon, a zone dominated by Isopora palifera, another by Acropora grandis, and the back reef flat margin. The trophic structure of fish assemblages largely differed at the higher level of organization. Zooplanktivores dominated on reef slopes, small microinvertivores on the reef front, and herbivores along with micro- and macroinvertivores on the inner reef flat. These results indicated different use of energy sources by highly structured fish assemblages within coral reefs. This study represents a 35 years old base line snapshot of fish assemblage structure across Yonge Reef, which could be used to evaluate the effect of the present ongoing climate change. [ABSTRACT FROM AUTHOR]