Trophic connectivity of deep-sea to pelagic fauna
Evaluating vertical trophic connectivity will allow researchers to examine the species that may serve as “vectors” between functional groups or to commercially valuable fisheries stocks. In addition, baseline stable isotope values of important model species can then be integrated with quantitative survey data in order to assign putative values of importance to the overall food web in the Gulf of Mexico ecosystem. Stomach content and stable isotope analyses will be focused on several key “model species” in order to provide information on the trophic connectivity of the ecosystem. Key model species will include both vertically migratory and non-migratory fish and invertebrate species with multiple feeding strategies including planktivores, zooplanktivores, gelativores, and piscivores. Information gained will improve our understanding of the vertical connectivity for migrating and non-migrating species throughout discrete depth zones (epi-, meso-, bathypelagic). Incorporation of this feeding component into the broader scope will enable researchers to draw connections among different trophic groups and provide data for ecosystem-based impact models.
Connectivity of deep-pelagic fishes using otolith chemistry
The degree of population connectivity for marine fishes is increasingly implicated as a key factor regulating population dynamics, and a variety of approaches have been used to assess movement and connectivity within and across ocean basins, including chemical markers in hard part such as otoliths (ear stones). The aim of this research component is to use natural, chemical markers in the otoliths of deep-pelagic taxa to assess ecological connectivity within the GoM. We will use two classes of chemical markers (trace elements, stable isotopes) to examine variation in chemical signatures of selected deep-pelagic taxa among distinct geographic locations in the northern GoM (NE, NC, NW regions). This research is based on the assumption that whole otolith chemistry represents a lifetime signature of environmental exposure for deep-pelagic taxa, and distinct spatial variation in otolith chemistry will be observed if dispersive histories or exchange of individuals from different within the GoM is limited. Our characterization of ecological connectivity of deep-pelagic fishes will contrast a series of “model” species with different life history and/or behavioral characteristics (e.g., vertical migration vs. no migration). Our working hypothesis is that some level of population exchange or mixing is expected within the GoM, with mixing more likely for migrating species that will be influenced to a greater degree by surface or subsurface currents within the basin.