Larval dispersal connects fish populations in a network of marine protected areas

Abstract

Networks of no-take marine protected areas (MPAs) have been widely advocated for the conservation of marine biodiversity. But for MPA networks to be successful in protecting marine populations, individual MPAs must be self-sustaining or adequately connected to other MPAs via dispersal. For marine species with a dispersive larval stage, populations within MPAs require either the return of settlement-stage larvae to their natal reserve or connectivity among reserves at the spatial scales at which MPA networks are implemented. To date, larvae have not been tracked when dispersing from one MPA to another, and the relative magnitude of local retention and connectivity among MPAs remains unknown. Here we use DNA parentage analysis to provide the first direct estimates of connectivity of a marine fish, the orange clownfish (Amphiprion percula), in a proposed network of marine reserves in Kimbe Bay, Papua New Guinea. Approximately 40% of A. percula larvae settling into anemones in an island MPA at 2 different times were derived from parents resident in the reserve. We also located juveniles spawned by Kimbe Island residents that had dispersed as far as 35 km to other proposed MPAs, the longest distance that marine larvae have been directly tracked. These dispersers accounted for up to 10% of the recruitment in the adjacent MPAs. Our findings suggest that MPA networks can function to sustain resident populations both by local replenishment and through larval dispersal from other reserves. More generally, DNA parentage analysis provides a direct method for measuring larval dispersal for other marine organisms.

Fig. 1.

Location maps and focal species. (A) LANDSAT satellite image of western Kimbe Bay showing the study sites. (B) Location of Kimbe Bay on the north side of New Britain, Papua New Guinea. (C) Aerial photograph of Kimbe Island showing lagoonal habitats in which A. percula are concentrated in the study area. (Photo courtesy of Tami Pelusi.) (D) A. percula sheltering in an anemone, Kimbe Bay. (Photo courtesy of Simon Thorrold.)

Fig. 2.

Map of locations of all anemones in each of 5 lagoons (A– E) that harbored adult or juvenile A. percula around Kimbe Island. (A) Location of anemones with adult A. percula that either produced larvae that subsequently settled into anemones around Kimbe Island (yellow symbols) or did not produce larvae that returned to Kimbe Island (black symbols). (B) Location of anemones with recently settled juvenile A. percula that either were progeny of Kimbe Island adults (red symbols) or had dispersed from reefs at least 6 km away from Kimbe Island (white circles).

Fig. 3.

Larval dispersal of A. percula from Kimbe Island to other designated marine reserves in western Kimbe Bay. (A) Proportion of recently settled juvenile A. percula collected at each of 4 locations that were progeny of Kimbe Island A. percula. The red boxes outline proposed reserve boundaries (6). (B) Location of adult A. percula that produced larvae that successfully dispersed and settled on anemones away from Kimbe Island (yellow symbols).