Development of enrichment of Brachionus plicatilis species complex for initial feeding to marine fish larvae

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Importance of intertidal seagrass beds as nursery area for coral reef fish juveniles (Mayotte, Indian Ocean)

International audienceThe present study highlights the importance of intertidal seagrass beds as nursery areas for coral reef fish juveniles along four sites (Mtsoubatsou, Sohoa, Boueni, Ngouja) on the western coast of Mayotte Island. The results collected by underwater visual census from November 2012 to January 2013 showed that mean total fish density between adults and juveniles varied significantly at each site, with juveniles always being more abundant in seagrass beds than adults. Of the total fish assemblages sampled in seagrass beds, 73% were juveniles and few adults of large species were observed. Overall, our study highlights the important functional role of intertidal seagrass beds for fish assemblages, as they are the primary habitat for the juveniles of many fish species on Mayotte reefs. Seagrass beds, however, are very vulnerable ecosystems and are decreasing worldwide. Therefore it is of primary importance to protect seagrass beds within the Indo-Pacific

Distribution patterns of ocellated eagle rays, Aetobatus ocellatus, along two sites in Moorea Island, French Polynesia

Elasmobranchs are critical to tourism industries worldwide. In French Polynesia, where ecotourism is the second most important industry, little is known about the spatiotemporal distribution of eagle rays. This study represents the first investigation into habitat use and behaviour of ocellated eagle rays (Aetobatus ocellatus) in French Polynesia focused on two sites with different levels of anthropogenic noise. Environmental variables and biological data were recorded over a one-year period to explore the distribution patterns of 113 eagle rays identified at these sites. Results revealed distinct patterns in-habitat use between the two sites, with the eagle ray population structured according to ontogenetic stage. Young rays preferred the site with lower levels of noise pollution, where they foraged at the end of the day. Adult eagle rays gathered in the mornings at the louder site, where the only noticeable activity was group swimming. Overall, our results could help conservation initiatives to manage this important species in French Polynesia, and potentially other coral reef areas, especially in the context of rising human impacts on the environment

Consistency in the supply of larval fishes among coral reefs in French Polynesia.

For marine fishes with a bipartite life cycle, pelagic larval dispersal can shape the distribution, connectivity, composition and resilience of adult populations. Numerous studies of larval dispersal, and associated settlement and recruitment processes, have examined the relationship between population connectivity and oceanographic features. However, relatively little is known about spatial and temporal variation in the abundance of larvae settling among different reefs and the extent to which the species assemblage of larvae settling at one location is reflective of the assemblage in neighbouring areas. Here, using crest nets, which provide a non-selective measure of the total abundance and assemblage of larvae settling to a reef (i.e. larval supply), we collected larval coral reef fishes at five locations surrounding two spatially disparate French Polynesian islands: Moorea and Nengo-Nengo. Overall, larval settlement patterns were correlated with the lunar cycle, with larval abundance peaking during the new moon. Although there were some spatial differences in larval supply among the five monitored sites, settlement patterns were largely consistent, even at the species level, irrespective of factors such as coastline orientation or distance between sites. This study provides further insights into the mechanisms driving patterns of dispersal and settlement of larval fishes over large spatial scales

Consistency in the supply of larval fishes among coral reefs in French Polynesia

<div><p>For marine fishes with a bipartite life cycle, pelagic larval dispersal can shape the distribution, connectivity, composition and resilience of adult populations. Numerous studies of larval dispersal, and associated settlement and recruitment processes, have examined the relationship between population connectivity and oceanographic features. However, relatively little is known about spatial and temporal variation in the abundance of larvae settling among different reefs and the extent to which the species assemblage of larvae settling at one location is reflective of the assemblage in neighbouring areas. Here, using crest nets, which provide a non-selective measure of the total abundance and assemblage of larvae settling to a reef (<i>i</i>.<i>e</i>. larval supply), we collected larval coral reef fishes at five locations surrounding two spatially disparate French Polynesian islands: Moorea and Nengo-Nengo. Overall, larval settlement patterns were correlated with the lunar cycle, with larval abundance peaking during the new moon. Although there were some spatial differences in larval supply among the five monitored sites, settlement patterns were largely consistent, even at the species level, irrespective of factors such as coastline orientation or distance between sites. This study provides further insights into the mechanisms driving patterns of dispersal and settlement of larval fishes over large spatial scales.</p></div

Comparisons of larval settlement patterns between nets.

<p>Comparisons of larval settlement patterns between nets.</p

Comparisons of species versus total settlement patterns.

<p>Comparisons of species versus total settlement patterns.</p

Study sites and crest net locations.

<p>(A) Location of French Polynesia within the Pacific Ocean. (B) Location of Moorea Island and Nengo-Nengo Atoll within French Polynesia. (C) Location of crest net sites. Grey triangles indicate crest net locations (M_W1 and M_W2 along the west coast of Moorea, NN_N on the north coast of Nengo-Nengo, and NN_SE1 and NN_SE2 along the south-east coast of Nengo-Nengo), as well as respective inflow orientations.</p

Larval settlement patterns in relation to lunar phases.

<p>Larval settlement patterns in relation to lunar phases.</p

Relative abundances of larvae in each crest net.

<p>Relative abundance of (A) all larval fishes, (B) <i>Acanthurus triostegus</i> larvae, (C) <i>Bothus mancus</i> larvae, (D) <i>Chromis viridis</i> larvae, (E) <i>Pristiapogon fraenatus</i> larvae. Green and dark green lines indicate M_W1 and M_W2 nets respectively while light blue, blue, and dark blue lines indicate NN_N, NN_SE1 and NN_SE2. Circular points indicate a crest net with a westward orientation, triangular points indicate a northward orientation and square points indicate a south-eastward orientation. Black and white circles above each panel indicate the lunar phases: new moon (black circle), first quarter, full moon (white circle) and last quarter.</p