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

Abstract

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.

Fig 1. Study sites and crest net locations.

(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.

Fig 2. Relative abundances of larvae in each crest net.

Relative abundance of (A) all larval fishes, (B) Acanthurus triostegus larvae, (C) Bothus mancus larvae, (D) Chromis viridis larvae, (E) Pristiapogon fraenatus 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.