Larval Dispersal and Retention Among Sub-populations of Coral Reef Fishes: A Multi-Technique Approach

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Population connectivity, the degree to which geographically-separated groups are linked by dispersal, is a critical parameter in the dynamics of marine populations. Connectivity rates determine colonization patterns of new habitats, the resiliency of populations to harvest, and the design of networks of No Take Marine Reserves (NTMRs). Quantifying exchange rates in marine organisms is extremely difficult because natal origins of adults are almost invariably unknown. This lack of knowledge is primarily due to the difficulty of conducting mark-recapture studies in species with large numbers of small pelagic offspring that suffer high initial mortality rates. This project will continue a multi-technique approach combining mass-marking of fish embryos using TRAnsgenerational Isotope Labeling (TRAIL) of otoliths and paternity analyses based on hypervariable microsatellite DNA markers to measure dispersal distances of coral reef fishes. Population connectivity will be estimated for two species (Amphiprion percula and Chaetodon vagabundus) in Kimbe Bay, Papua New Guinea. Coral reef organisms are usually distributed across a mosaic of reefs that are sometimes separated by the ocean. It has been presumed that at small scales, reefs must be open populations, with significant exchange of larvae among neighboring reefs. At larger scales, populations must effectively be closed, with late-stage larvae returning to the same population as their parents. The scale over which this transition takes place is unknown. Recent evidence suggests that ecologically significant self-recruitment may occur at scales of individual reefs or islands. If accurate, these findings have important implications for management strategies for marine species, including the design of networks of NTMRs, because knowledge of dispersal distances determines the scale over which populations can be completely protected. It also determines the appropriate spacing of reserves to allow protected populations to replenish adjacent fished areas. This project will quantify population connectivity of coral reef fishes in Kimbe Bay, Papua New Guinea and broaden the spatial scale from examining the fate of larvae spawned at a single location (Kimbe Island) to examining connectivity among 5 designated NTMRs.The project will strengthen international collaborations among researchers from the US, Australia and France with expertise in otolith geochemistry, reef fish ecology, and population genetics. This collaboration includes the training of a graduate student. Research from the project will also be incorporated into courses taught by the PI. The research is highly relevant to ongoing conservation efforts in Kimbe Bay (led by The Nature Conservancy) and a new and ambitious six-nation effort to protect and manage coral reefs within the Coral Triangle. A major focus of the Coral Triangle Initiative will be ecosystem-based management and the design and implementation of a network of NTMRs. Estimates of population connectivity will, therefore, be vital to establish a strong scientific basis for management efforts.