We examined the pattern of development of assemblages of coral reef fishes on artificial reefs at One Tree Reef, Great Barrier Reef. Two sets of 8 reefs were built. To investigate the effects of habitat structure on species diversity, each set consisted of replicate pairs of 4 different reef types: plain (no holes), small-holed, medium-holed, and large-holed reefs. To examine seasonal differences in colonization, I set was established in summer (October 1971) and the other set in winter (July 1972). Visual censuses of the reefs' fish assemblages were made at monthly intervals over 32 mo (summer set) and 23 mo (winter set).We recorded a total of 105 resident species from the artificial reefs. Although less diverse, the fish assemblages differed little in terms of species composition from those of small natural patch reefs. Artificial reefs showed a high between-reef variability in species composition that was largely unrelated to habitat structure. Competitive interactions between species appeared unimportant in explaining the distribution of species between reefs. Likewise, possible positive associations between species were indicated for only a few species.Almost all settlement of the artificial reefs was by juvenile fishes. Recruitment was markedly seasonal and occurred mainly over summer (September-May). Juvenile recruitment patterns showed little year-to-year constancy. Most species tested showed nonrandom, clumped patterns of settlement on replicate reefs. More than half of species tested showed no significant differences in numbers of individuals which settled on different reefs, but the remainder showed significantly greater settlement on some reefs, suggesting habitat selection. For a few species, there was also greater recruitment to reefs already occupied by conspecifics, suggesting possible social facilitation of settlement. For most species, there were no significant interspecific interactions between adults and newly settling juveniles.Between-census variability in species composition was high and species turnover ranged from =17% of species/mo in winter to =39% in summer. Maximum times of persistence for most species were < 12 mo, and for many individuals survivorship was of the order of only a few months. Much of the high turnover appears due to losses through predation.There was no evidence that a persistent species equilibrium was attained during colonization. Because of predation and the seasonally varying, uncertain nature of recruitment, we see the development of any long-term species equilibrium as unlikely. We suggest that nonequilibrium conditions are a characteristic of coral reef fish communities and that because of these conditions, high withinhabitat diversities are maintained.

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lord Howe Island, some 630 kilometres off the northern coast of New South Wales, Australia at 31.5° South latitude, is the world's southern most locality with a well developed coral reef community and associated lagoon. An extensive collection of fishes from lord Howelsland was made during a month's expedition in February 1973. A total of 208 species are newly recorded from lord Howe Island and 23 species newly recorded from the Australian mainland. The fish fauna of lord Howe is increased to 447 species in 107 families. Of the 390 species of inshore fishes, the majority (60%) are wide-ranging tropical forms; some 10% are found only at lord Howe Island, southern Australia and/or New Zealand. less than 4% of the shore fishes are endemic to the lord Howe region (including Norfolk Island). Some 32% of the inshore species are restricted to the southwestern or southern Pacific Ocean.

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Behaviour of chaetodontid fishes relevant to Lorenz's “poster colouration” hypothesis has been studied. Field observations of 20 species at Lizard Island, Great Barrier Reef, showed that these chaetodontids rove over large areas of reef, occurring singly or in pairs and sometimes sizeable groups. The behaviour of chaetodontids does not support the supposed explanation of poster colours as intra‐specific sign stimuli serving to space individuals. During daytime, agonistic encounters are rare, even amongst groups, and for most species there is no evidence of territoriality. Experiments presenting painted and blank chaetodontid models to eight species generally confirmed these observations. At dusk and dawn, chaetodontids are aggressive and defend regular night‐resting places. Agonistic encounters though, are both intra‐ and inter‐specific; they serve to space individuals over only very small distances, and colouration seems to have little warning value. The question of the functional significance of poster colours remains largely unsolved. Amongst chaetodontids, territoriality clearly is not a major function and the evidence suggests that other kinds of social communication, as well as predator avoidance, have probably been important in the evolution of poster colouration.

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