Pelagic to demersal transition in a coral-reef fish, the orbicular batfish Platax orbicularis.

Behavioural and ecological observations were made on young, reared Platax orbicularis in Opunohu Bay, Moorea, French Polynesia, during their transition from the pelagic, dispersive stage to the reef-orientated demersal stage. Seventy-two young P. orbicularis (17-75 mm standard length, LS ) were released in the pelagic zone and 20 (40-70 mm LS ) adjacent to the reefs. Swimming speed was slow (mean 5·2 cm s(-1) ) and independent of size. An ontogenetic descent was observed: the smallest P. orbicularis swam at the surface, medium-sized P. orbicularis swam in midwater (mean 5-13 m) and the largest P. orbicularis swam to the bottom, where many lay on their sides. Platax orbicularis swam southerly on average, away from the ocean and into the bay. Smaller P. orbicularis were more likely to swim directionally than larger individuals. Young P. orbicularis released near reef edges swam at similar, but more variable speeds (mean 6·6 cm s(-1) ). About half of those released near reefs swam away, but fewer swam away from an inshore fringing reef than from a patch reef near the bay mouth. Many P. orbicularis swam up the slope onto the reef top, but the little settlement observed was near the reef base. Average, near-reef swimming direction was also southerly. Some reef residents, in particular the triggerfish Balistapus undulatus, harassed young P. orbicularis.

Marine fish communities in shallow volcanic habitats.

This survey of the marine ichthyofauna of the Piton de La Fournaise volcano at Reunion Island is the first explanatory study of fish community structures in this area. It describes and analyses the main qualitative descriptors of the fish communities (i.e. species richness, diet, life history and geographical distribution) and their spatio-temporal organization. This investigation in 2011 examined lava flows of different ages, including the most recent flows that entered the ocean between 1977 and 2007. In all, 263 species belonging to 45 families were observed. Overall, the fish community was notable for an absence of top predators and a predominance of opportunistic small-bodied species, with dietary flexibility and high reproductive rates, characteristic of the early stages of ecological succession. Between-site analysis indicated that the fish assemblages differed essentially according to the intensity of the last volcanic disturbances. Fish communities in the most disturbed sites showed the highest numbers of Serranidae and the highest proportions of omnivores and small-bodied opportunistic carnivores, including a high proportion of endemic south-western Indian Ocean species. The spatial pattern of this last category of species could be the result of convergent biological traits, and their adaptation to unstable environments at the expense of their competitiveness in more biodiverse, mature communities. Conversely, fish communities in the less disturbed sites showed the highest number of Holocentridae and the highest proportion of browsers of sessile invertebrates. This last characteristic could be a consequence of higher ecological maturity, illustrated by a more specialized trophic network, for assemblages in areas with less intense disturbances. Otherwise, high structural complexity, either in unconsolidated lava boulders, rocks and rubble or high coral-covered sites, could favour the increase of the total number of species independent of disturbance intensity. Regarding the broader effects, this study helps better understand how ecosystems can resist or recover from acute disturbances and the process of ecological succession that leads to the establishment of fish communities in newly submerged habitats.

Plasma cortisol and 11-ketotestosterone enzyme immunoassay (EIA) kit validation for three fish species: the orange clownfish Amphiprion percula, the orangefin anemonefish Amphiprion chrysopterus and the blacktip reef shark Carcharhinus melanopterus.

Commercially available enzyme immunoassay (EIA) kits were validated for measuring steroid hormone concentrations in blood plasma from three fish species: the orange clownfish Amphiprion percula, the orangefin anemonefish Amphiprion chrysopterus and the blacktip reef shark Carcharhinus melanopterus. A minimum of 5 microl plasma was required to estimate hormone concentrations with both kits. These EIA kits are a simple method requiring minimal equipment, for measuring hormone profiles under field conditions.

Identical digeneans in coral reef fishes from French Polynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules.

Three coral reef fish species, Zanclus cornutus, Chaetodon vagabundus and Naso lituratus, were collected in French Polynesia and on the Great Barrier Reef, Queensland. These fish species were each infected by one morphologically similar digenean species in both localities; Schistorchis zancli Hanson, 1953 was found in Zanclus cornutus, Preptetos laguncula Bray and Cribb, 1996 in Naso lituratus and Neohypocreadium dorsoporum Machida and Uchida, 1987 in Chaetodon vagabundus. In addition, on the Great Barrier Reef P. laguncula was also found in Naso unicornis and N. dorsoporum in Chaetodon ephippium and Chaetodon flavirostris. Morphometric differences between the species from the two sites were only slight. Sequences from the second internal transcribed spacer of the ribosomal DNA of each worm revealed total homology or negligible divergence between samples from hosts caught in French Polynesia and on the Great Barrier Reef. These results show that across more than 6000 km these digeneans are similar in morphology and genotype. Some species of fishes and molluscs are considered to have distributions that encompass the entire tropical Indo-West Pacific. These findings suggest that at least some of their parasites have similarly broad distributions.

Endoparasite species richness of new caledonian butterfly fishes: host density and diet matter.

Ecological factors may influence the number of parasites encountered and, thus, parasite species richness. These factors include diet, gregarity, conspecific and total host density, habitat, body size, vagility, and migration. One means of examining the influence of these factors on parasite species richness is through a comparative analysis of the parasites of different, but related, host species. In contrast to most comparative studies of parasite species richness of fish, which have been conducted by using data from the literature, the present study uses data obtained by the investigators. Coral reef fishes vary widely in the above ecological factors and are frequently parasitized by a diverse array of parasites. We, therefore, chose to investigate how the above ecological factors influence parasite species richness in coral reef fishes. We investigated the endoparasite species richness of 21 species of butterfly fishes (Chaetodontidae) of New Caledonia. We mapped the diet characters on the existing butterfly fish phylogeny and found that omnivory appears to be ancestral. We also mapped the estimated endoparasite species richness, coded from low to high parasite species richness, on the existing butterfly fish phylogeny and found that low parasite species richness appears to be associated with the ancestral state of omnivory. Different dietary and social strategies appear to have evolved more than once, with the exception of obligate coralivory, which appears to have evolved only once. Finally, after controlling for phylogenetic relationships, we found that only the percentage of plankton in the diet and conspecific host density were positively correlated with endoparasite species richness.

Parasites of recruiting coral reef fish larvae in New Caledonia.

Recruiting coral reef fish larvae from 38 species and 19 families from New Caledonia were examined for parasites. We found 13 parasite species (Platyhelminthes: Monogenea, Cestoda and Trematoda) but no acanthocephalan, crustacean or nematode parasites. Over 23% of individual fish were infected. Didymozoid metacercariae were the most abundant parasites. We conclude that most of the parasites are pelagic species that become 'lost' once the fish larvae have recruited to the reef. Larval coral reef fish probably contribute little to the dispersal of the parasites of the adult fish so that parasite dispersal is more difficult than that of the fish themselves.

Parasite diversity/host age and size relationship in three coral-reef fishes from French Polynesia.

The parasite communities of three coral-reef fish species (Stegastes nigricans, Dascyllus aruanus and Cephalopholis argus) were on Tiahura reef, French Polynesia. The age and growth of each fish was analysed by otolith increment counts and a significant correlation between these variables was found. Stegastes nigricans was parasitised by six adult parasite species, D. aruanus by two adult parasite species and C. argus by five adult parasite species. The most common parasite species were found in all fish size classes. Ectoparasites showed a positive relationship between their abundance and host body length for all three reef fish species. A positive relationship was found only between host size and parasite abundance for common endoparasite species. Parasite species richness, Brillouin's diversity index, and host size and age were positively related. Finally, we discuss the influence of different biological (host diet, host immune response, parasite life-cycle) and ecological factors on parasite community structure in these three reef fishes. Host diet quality seems to be one of the major factors affecting the endoparasite community structure in these reef fishes. Ectoparasite communities seem to be influenced more by biological factors such as, for example, host immunity for the caligid larvae or parasite life-cycle for the gnathiid praniza larvae. In addition, the effect of ecological factors such as cleaning symbiosis on these ectoparasites cannot be dismissed.