The short-lived neon damsel Pomacentrus coelestis: implications for population dynamics.

Daily increments of Pomacentrus coelestis, an abundant and well-studied fish, were validated for the life of the fish and depending on the location, age-maxima were estimated to be 127-160 days on reefs separated by tens to hundreds of kilometres on the Great Barrier Reef. This contrasts with congeners and other damselfishes that live for 5 years or more. Otoliths of P. coelestis were thinner and had different patterns of banding when compared with relatively long-lived congeners. It is suggested that banding patterns in P. coelestis may be related to patterns of maturation and spawning. The consequences of a short life would have a great influence on the population dynamics of this widespread species. Further, the demographics and habitat preferences of this species suggest rapid colonization and establishment of breeding populations that would quickly change the relative abundance of sympatric fishes.

Distributions and habitat associations of the bridled monocle bream Scolopsis bilineatus (Nemipteridae): a demographic approach.

This study focussed on the demography and ecology of Scolopsis bilineatus at three locations on the Great Barrier Reef: the Lizard Island Group, Orpheus Island and One Tree Island. Scolopsis bilineatus lived for up to 16 years and had four distinct life-history stages, which varied in their distribution patterns, habitat use and reproductive behaviour. Pre-maturational sex change occurred whereby all males were derived from immature females, and males grew faster and larger than females. Small females and larger males generally formed pairs, which influenced their spatial distributions at small scales. Distributions of S. bilineatus were influenced by depth and exposure within reefs, particularly for juveniles, and most fish were found in shallow, sheltered habitats. Abundance was influenced by benthic cover, and was higher in areas of high coral cover and low where algae were abundant. Habitat associations were stronger at the microhabitat scale, and shelter sites were important for adults. Ontogenetic changes in microhabitat associations were found: juveniles occupied sand and rubble, and adults occupied shelters such as caves and overhangs. Adults showed site fidelity for shelter sites over a period of 4 days and returned to specific shelter sites repeatedly. These findings illustrate the importance of understanding the spatial ecology and habitat use of coral reef fishes, particularly with reference to size-based changes within species.

Eight microsatellite loci for the Irukandji syndrome-causing carybdeid jellyfish, Carukia barnesi (Cubozoa, Cnidaria).

Microsatellites are high-resolution genetic markers that may be applied to examine parentage, population structure and the direction and extent of dispersal. Here we present eight polymorphic microsatellite loci developed for the carybdeid jellyfish, Carukia barnesi. The loci were developed from a microsatellite-enriched, partial genomic DNA library and tested for polymorphism on animals from each of two geographically distinct populations, Lizard Island and Double Island, from the Great Barrier Reef. The number of alleles observed for each locus ranged from 7 to 19.

Dispersal in the spiny damselfish, Acanthochromis polyacanthus, a coral reef fish species without a larval pelagic stage.

The spiny damselfish, Acanthochromis polyacanthus, is widely distributed throughout the Indo-Australian archipelago. However, this species lacks a larval dispersal stage and shows genetic differentiation between populations from closely spaced reefs. To investigate the dispersal strategy of this unique species, we used microsatellite markers to determine genetic relatedness at five dispersal scales: within broods of juveniles, between adults within a collection site (approximately 30 m(2)), between sites on single reefs, between nearby reefs in a reef cluster, and between reef clusters. We sampled broods of juveniles and adults from seven reefs in the Capricorn-Bunker and Swain groups of the Great Barrier Reef. We found that extra-pair mating is rare and juveniles remain with their parents until fledged. Adults from single sites are less related than broods but more related than expected by chance. However, there is no evidence of inbreeding suggesting the existence of assortative mating and/or adult migration. Genetic differences were found between all of the reefs tested except between Heron and Sykes reefs, which are separated only by a 2-km area of shallow water (less than 10 m). There was a strong correlation between genetic distance, geographical distance and water depth. Apparently, under present-day conditions spiny damselfish populations are connected only between sites of shallow water, through dispersal of adults over short distances. Assuming that dispersal behaviour has not changed, the broad distribution of A. polyacanthus as a species is likely based on historical colonization patterns when reefs were connected by shallow water at times of lower sea levels.

Organochlorine pesticides and hexachlorobenzene along the central coast of New South Wales: multi-scale distributions using the territorial damselfish Parma microlepis as an indicator.

Concentrations of 10 organochlorine pesticides and hexachlorobenzene (HCB) were determined in the territorial damselfish Parma microlepis at three urban locations and three reference locations centred on the Sydney region. Dieldrin, HCB and DDE were the most frequently detected organochlorines, occurring in 70-100% of samples collected. Alpha and gamma chlordane were also reasonably common and occurred in more than 30% of the samples. Each organochlorine compound investigated had a distinct spatial pattern of distribution. Related chemicals such as alpha and gamma chlordane, and DDT, DDE and DDD tended to have similar patterns of distribution. There were clear differences in patterns of distribution in organochlorines between urban and reference locations shown using non-parametric multivariate techniques. Relative variability of samples from urban locations was higher than at reference locations in 1993, but there was no consistent pattern of differences in the dispersions of samples among urban and reference locations in 1994. Age and condition indices (K) showed no association with total concentrations of organochlorine residues in fish. Significant, but weak associations were found between organochlorine residues and size, gonad somatic and liver somatic indices.