Microhabitat use of juvenile coral reef fish in Palau

While relationships between adult fish density and structural habitat features are well established, relatively little is known about the habitat associations of juvenile reef fish. In a reserve system in Palau, we quantified microhabitat association with juvenile reef fish community structure, and determined the influence of foraging space, predator size and confamilial attraction on juvenile and adult pomacentrid abundance. Habitat structure and juvenile reef fish communities differed significantly among microhabitats with one exception: no difference was found between foliose and consolidated rubble microhabitats. Overall, pomacentrids characterised the juvenile community structure of each microhabitat. The abundance of early juvenile pomacentrids is simultaneously determined by microhabitat structure and predator size, with little evidence for settlement selection near adults. The results also suggest that the influence of habitat structure become weaker with ontogeny which in part, drives large predators to negatively influence the abundance of adult pomacentrids. The results have important implications on management, specifically in prioritizing areas for protection, and in modeling the impacts of habitat loss on reef fish communities

Delineating Optimal Settlement Areas of Juvenile Reef Fish in Ngederrak Reef, Koror State, Republic of Palau

Establishing the effectiveness of habitat features to act as surrogate measures of diversity and abundance of juvenile reef fish provides information that is critical to coral reef management. When accurately set on a broader spatial context, microhabitat information becomes more meaningful and its management application becomes more explicit. The goal of the study is to identify coral reef areas potentially important to juvenile fishes in Ngederrak Reef, Republic of Palau, across different spatial scales. To achieve this, the study requires the accomplishment of the following tasks: (1) structurally differentiate the general microhabitat types using acoustics; (2) quantify microhabitat association with juvenile reef fish community structure; and (3) conduct spatial analysis of the reef-wide data and locate areas optimal for juvenile reef fish settlement. The results strongly suggest the importance of branching structures in determining species count and abundance of juvenile reef fish at the outer reef slope of Ngederrak Reef. In the acoustic map, the accurate delineation of these features allowed us to identify reef areas with the highest potential to harbor a rich aggregation of juvenile reef fish. Using a developed spatial analysis tool that ranks pixel groups based on user-defined parameters, the reef area near the Western channel of Ngederrak is predicted to have the most robust aggregation of juvenile reef fish. The results have important implications not only in management, but also in modeling the impacts of habitat loss on reef fish community. At least for Ngederrak Reef, the results advanced the utility of acoustic systems in predicting spatial distribution of juvenile fish

Benthic components that made the greatest contribution to dissimilarity among zones.

<p>Mean <b>%</b> cover (± SE) of the benthic components identified by SIMPER analyses as major contributors to the dissimilarity in benthic community structure among zones (fished = blue, no-take = green, no-entry = pink) in each sub-region (a-f). Significant differences between reserves (i.e. no-take vs no-entry) were only found in northern mid-shelf reefs and outer-central reefs. Sedim/turf = sediment-laden turfs.</p

Characterization of surveyed reef sites.

<p>Characterization of surveyed reef sites.</p

Location of reefs sites surveyed on the northernmost section of the GBR.

<p>The legend on the top left indicates the color code to reference each reef by shelf location and management status. Sources: GBRMPA datasets: Great Barrier Reef Features (Version 1.2), Special Management Areas (v1.0), Marine Bioregions of the Great Barrier Reef (Reef) (v2.0). Retrieved from <a href="http://www.gbrmpa.gov.au/geoportal" target="_blank">http://www.gbrmpa.gov.au/geoportal</a>. Map created using ArcGIS® software by Esri.</p

PERMANOVA results on benthic community and fish biomass structure.

<p>PERMANOVA results on benthic community and fish biomass structure.</p

Principle Coordinate Analysis (PCO) of benthic cover.

<p>Ordination plots show (a) reef sites along the first two axes based on shelf position, (b) overlay of vectors based on Spearman correlations. Strongest correlations (> 0.5) shown in red. Cover data were square-root transformed for analyses.</p

Principle Coordinate Analysis (PCO) of the assemblage structure of non-fished species.

<p>Plots show (a) ordination of reef sites along PCO1indicating shelf position, (b) within reef variability along PCO2 (separation of replicate sites of same reef), (c) species with strongest associations (Spearman >0.5) to PCO2: pomacentrids are shown in black, (d) Observer’s identity associated with PCO2 variability, and (e) variation in biomass of <i>P</i>. <i>leopardus</i> along PCO2. Biomass was log+1 transformed for analyses.</p

Principle Coordinate Analysis (PCO) of the assemblage structure of targeted carnivores.

<p>(a) ordination of reef sites along the first axes (PCO1, PCO2) following shelf position, (b) species of highly targeted (red) and less-targeted (blue) carnivores that show the strongest correlation (Spearman >0.5) to PCO, (c) ordination following sub-regions. Dotted circle denotes inshore reefs (<50 km from shore) and (d) management zones. Biomass was log+1 transformed for analyses.</p

Summary of linear mixed models testing zoning and habitat effects on fish biomass.

<p>Summary of linear mixed models testing zoning and habitat effects on fish biomass.</p