Search

Nous présentons ici les relations longueur-poids (LWR) pour 11 espèces de poissons de récif corallien de huit îles de Polyné- sie française. Au total, 1930 poissons ont été collectés dans cinq îles de l’archipel de la Société (Moorea, Tahiti, Raiatea, Huahine, Tetiaroa) et dans trois atolls de l’archipel des Tuamotu (Takapoto, Tikehau et Rangiroa). Ces poissons couvrent plusieurs niveaux trophiques, avec des planctonophages, des herbivores et des carni- vores, et sont parmi les espèces les plus abondantes de la région. Les estimations comprennent des LWR pour des espèces qui n’ont jamais été publiées auparavant ou qui ne sont pas disponibles dans la littérature ou les bases de données accessibles. Les mesures de longueur totale (TL : précision de 0,1 cm) et de poids total (P : pré- cision de 0,01 g) ont été effectuées. Ces estimations augmentent le nombre de LWR disponibles et robustes pour les poissons des récifs coralliens, ce qui permet de mieux comprendre la croissance de ces espèces. Avec un focus plus particulier sur les espèces de petite taille, parmi les plus abondantes observées lors des compta- ges visuels sous-marins, ces estimations permettront aux gestion- naires des ressources marines et aux scientifiques locaux de carac- tériser les biomasses de poissons en Polynésie française avec une plus grande précision [ABSTRACT FROM AUTHOR]

Aim: Identification of the processes that generate and maintain species diversity within the same region can provide insight into biogeographic patterns at broader spatiotemporal scales. Hawkfishes in the genus Paracirrhites are a unique taxon to explore with respect to niche differentiation, exhibiting diagnostic differences in coloration, and an apparent center of distribution outside of the Indo–Malay–Philippine (IMP) biodiversity hotspot for coral reef fishes. Our aim is to use next‐generation sequencing methods to leverage samples of a taxon at their center of maximum diversity to explore phylogenetic relationships and a possible mechanism of coexistence. Location: Flint Island, Southern Line Islands, Republic of Kiribati. Methods: A comprehensive review of museum records, the primary literature, and unpublished field survey records was undertaken to determine ranges for four "arc‐eye" hawkfish species in the Paracirrhites species complex and a potential hybrid. Fish from four Paracirrhites species were collected from Flint Island in the Southern Line Islands, Republic of Kiribati. Hindgut contents were sequenced, and subsequent metagenomic analyses were used to assess the phylogenetic relatedness of the host fish, the microbiome community structure, and prey remains for each species. Results: Phylogenetic analyses conducted with recovered mitochondrial genomes revealed clustering of P. bicolor with P. arcatus and P. xanthus with P. nisus, which were unexpected on the basis of previous morphological work in this species complex. Differences in taxonomic composition of gut microbial communities and presumed prey remains indicate likely separation of foraging niches. Main Conclusions: Our findings point toward previously unidentified relationships in this cryptic species complex at its proposed center of distribution. The three species endemic to the Polynesian province (P. nisus, P. xanthus, and P. bicolor) cluster separately from the more broadly distributed P. arcatus on the basis of relative abundance of metazoan sequences in the gut (presumed prey remains). Discordance between gut microbial communities and phylogeny of the host fish further reinforce the hypothesis of niche separation. [ABSTRACT FROM AUTHOR]

We take advantage of a natural gradient of human exploitation and oceanic primary production across five central Pacific coral reefs to examine foraging patterns in common coral reef fishes. Using stomach content and stable isotope (δ15N and δ13C) analyses, we examined consistency across islands in estimated foraging patterns. Surprisingly, species within the piscivore–invertivore group exhibited the clearest pattern of foraging consistency across all five islands despite there being a considerable difference in mean body mass (14 g–1.4 kg) and prey size (0.03–3.8 g). In contrast, the diets and isotopic values of the grazer–detritivores varied considerably and exhibited no consistent patterns across islands. When examining foraging patterns across environmental contexts, we found that δ15N values of species of piscivore–invertivore and planktivore closely tracked gradients in oceanic primary production; again, no comparable patterns existed for the grazer–detritivores. The inter-island consistency in foraging patterns within the species of piscivore–invertivore and planktivore and the lack of consistency among species of grazer–detritivores suggests a linkage to different sources of primary production among reef fish functional groups. Our findings suggest that piscivore–invertivores and planktivores are likely linked to well-mixed and isotopically constrained allochthonous oceanic primary production, while grazer–detritivores are likely linked to sources of benthic primary production and autochthonous recycling. Further, our findings suggest that species of piscivore–invertivore, independent of body size, converge toward consuming low trophic level prey, with a hypothesized result of reducing the number of steps between trophic levels and increasing the trophic efficiency at a community level. [ABSTRACT FROM AUTHOR]

Abstract: Human impacts on ecosystems can decouple the fundamental ecological relationships that create patterns of diversity in free‐living species. Despite the abundance, ubiquity, and ecological importance of parasites, it is unknown whether the same decoupling effects occur for parasitic species. We investigated the influence of fishing on the relationship between host diversity and parasite diversity for parasites of coral reef fishes on three fished and three unfished islands in the central equatorial Pacific. Fishing was associated with a shallowing of the positive host‐diversity–parasite‐diversity relationship. This occurred primarily through negative impacts of fishing on the presence of complex life‐cycle parasites, which created a biologically impoverished parasite fauna of directly transmitted parasites resilient to changes in host biodiversity. Parasite diversity appears to be decoupled from host diversity by fishing impacts in this coral reef ecosystem, which suggests that such decoupling might also occur for parasites in other ecosystems affected by environmental change. [ABSTRACT FROM AUTHOR]

Fisheries exploitation represents a considerable threat to coral reef fish resources because even modest levels of extraction can alter ecological dynamics via shifts of stock size, species composition, and size-structure of the fish assemblage. Although species occupying higher trophic groups are known to suffer the majority of exploitative effects, changes in composition among lower trophic groups may be major, though are not frequently explored. Using size-based biomass spectrum analysis, we investigate the effects of fishing on the size-structure of coral reef fish assemblages spanning four geopolitical regions and determine if patterns of exploitation vary across trophic groups. Our analyses reveal striking evidence for the variety of effects fisheries exploitation can have on coral reef fish assemblages. When examining biomass spectra across the entire fish assemblage we found consistent evidence of size-specific exploitation, in which large-bodied individuals experience disproportionate reductions. The pattern was paralleled by and likely driven by, strongly size-specific reductions among top predators. In contrast, evidence of exploitation patterns was variable among lower trophic groups, in many cases including evidence of reductions across all size classes. The breadth of size classes and trophic groups that showed evidence of exploitation related positively to local human population density and diversity of fishing methods employed. Our findings highlight the complexity of coral reef fisheries and that the effects of exploitation on coral reefs can be realized throughout the entire fish assemblage, across multiple trophic groups and not solely restricted to large-bodied top-predators. Size-specific changes among fishes of lower trophic groups likely lead to altered ecological functioning of heavily exploited coral reefs. Together these findings reinforce the value of taking a multi-trophic group approach to monitoring and managing coral reef fisheries. [ABSTRACT FROM AUTHOR]

The article discusses a survey which can be used to assess populations of coral reef fishes in which a pair of SCUBA divers maneuver towboard dive plans and record of large-bodied reef fishes while being towed at slow speed behind a small boat. It cites the main objectives in sampling coral reef fish communities. According to the authors, the towed-diver method provides managers and scientists with a tool to assess the distribution and status of reef fish stocks.

This paper describes the results of a field survey designed to test the prediction that the density of benthic juveniles of shallow-reef fishes is greater on wind-wave “exposed” sectors of a pair of isolated oceanic atolls (Kure, Pearl and Hermes) at the far northwestern end of the Hawaiian Islands, an archipelago in which east-northeasterly trade winds dominate onshore water flow and transport by surface currents. The densities of recruits (juveniles ≤5 cm total length) were higher overall on windward versus leeward sectors of carbonate rock-rubble back reefs at both atolls, and the pattern was stronger for smaller (likely younger, more recently settled) recruits of four of the five most abundant species and the remainder pooled as an “Other” taxon. The windward-leeward disparity was four-fold greater at Pearl Hermes (the atoll with a three-fold longer perimeter) than at Kure. Resident predator biomass also was correlated with recruit densities, but habitat (benthic substratum) effects were generally weak. The distribution and abundance of recruits and juveniles of the primarily endemic reef fishes on shallow back reefs at these atolls appear partly influenced by relative rates of water flow over windward vs. leeward sectors of barrier reef and by the size, shape, and orientation of habitat parcels that filter out postlarval fishes with relatively weak swimming capabilities like labroids. Whole-reef geomorphology as well as fine-scale habitat heterogeneity and rugosity should be considered among the suite of many factors used to interpret observed spatial patterns of post-settlement juvenile fish distribution at atolls and perhaps some other tropical reefs. [ABSTRACT FROM AUTHOR]