Population and Migratory Connectivity in Ocean Ecosystems
Population Connectivity in Coral Reef Fishes
A central goal of marine ecology is to achieve a mechanistic understanding of the factors regulating the abundance and distribution of marine populations. One critical component of the above goal is to quantify rates of exchange, or connectivity, among subpopulations of marine organisms via larval dispersal. Theoretical studies suggest that these linkages play a fundamental role in local and metapopulation dynamics, community structure, genetic diversity, and the resiliency of populations to human exploitation. Understanding population connectivity is also key in efforts to develop spatial management methods for marine-capture fisheries, including the design of networks of marine reserves. This work currently focuses on using DNA parentage analysis to empirically measure dispersal kernels and test the accuracy of coupled bio-physical models that we have developed for our study site in Kimbe Bay, Papua New Guinea.
We have developed a novel mass-marking technique, transgenerational Isotope Labeling (TRAIL), and DNA parentage analyses to generate empirical estimates of larval dispersal in fish populations inhabiting coral reefs in Papua New Guinea. The relative importance of retention and connectivity will be measured on both regional and local scales. The project, in collaboration with Dr. Geoffrey Jones (James Cook University) and Dr. Serge Planes (University of Perpignon), is funded by National Science Foundation and the Australian Research Council. The first paper from this research was featured on the cover of Current Biology (Jones et al., 2005), and more recently the first field application of the TRAIL technique was published in Science (Almany et al., Science, 2007).
We are also working on coral reef food webs using compound-specific stable isotope analyses (SIA). Traditional bulk carbon and nitrogen stable isotope analyses are generally not sufficiently powerful for use in these systems, but SIA of specific amino acids shows considerable promise. We have already demonstrated the use of this approach for examining movements of juvenile snappers through a coral reef seascape in the Saudi Arabian Red Sea (McMahon et al., Proc. Natl. Acad. Sci., 2012). We are now turning our attention to the flow of C and N through relatively pristine reefs in the Red Sea, central Pacific and Indian Oceans.
Finally, we continue to develop techniques for trace element and stable isotope analyses of fish otoliths. Focusing on high precision in situ analyses of otolith geochemistry using laser probes and sector field inductively coupled plasma mass spectrometry (ICP-MS), we are developing methods for determining isotopic ratios of selected elements in the otoliths of marine and anadromous fishes. Isotopic ratios are assayed using a Thermo-Finnigan Neptune multiple collector ICP-MS in WHOI’s Inductively Coupled Plasma facility. One application of this approach will involve determining natal locations of juvenile American shad, collected from rivers along the east coast of the United States. Trace element and stable C and O isotope ratio signatures in these otoliths are being combined with high precision Sr isotope measurement to increase the confidence with which adult shad can be assigned to natal river based on these natural geochemical signatures (e.g. Walther and Thorrold, Can. J. Fish. Aquat. Sci., 2010).
Migratory Connectivity of Oceanic Fishes – The TOTEM Project
The largest fishes roaming our oceans are among the most spectacular, and endangered, species on earth. Yet despite their size and threatened status, we know remarkably little about the teleosts (tunas and swordfish) and elasmobranchs (sharks and rays) that constitute planet ocean’s marine fish megafauna. This lack of knowledge directly impacts our ability to conceive and implement effective conservation efforts for these species, and more generally our efforts to understand the structure and functioning of ocean ecosystems. The Tagging of Oceanic Teleost and Elasmobranch Megafauna (TOTEM) project aims to address this knowledge gap by developing and deploying pop-up satellite archival transmitting (PSAT) tags on swordfish, tunas, sharks and rays. The project was launched in the summer of 2012 with tagging expeditions to offshore canyons of southern New England waters and the Azores. We envisage that the TOTEM project will leverage private philanthropic and government funds to provide a unique view of the lives of the largest fishes in the oceans. These data will in turn be shared with appropriate governmental, inter-governmental and non-governmental organizations tasked with the conservation and sustainable management of these populations in the Atlantic.