Trends and Drivers of Faunal Abundance in the Offshore Gulf of Mexico: Narrowing the Largest Data Gap in the Gulf\u27s Large Marine Ecosystem

The deep-pelagic is simultaneously the Gulf of Mexico’s largest and least known habitat. The Deepwater Horizon oil spill (DWHOS) highlighted this massive data gap – no data were available to assess the injury to the offshore water-column fauna. The authors of this proposal executed two large-scale programs that have narrowed this gap considerably, though much work remains. These programs (ONSAP & DEEPEND) have detected large declines in the abundance of the offshore fauna since DWHOS. This proposal seeks support to link data obtained between 2010-18 with new data (2020-24) in order to ascertain the long-term trends in this ecosystem. The reasons for resource management to be concerned about the offshore Gulf fauna are many. The oceanic Gulf is one of four ‘hyperdiverse’ deep-pelagic ecoregions on Earth. Such diversity is central to efforts to protect the open ocean. Further, a significant portion of the Gulf’s offshore diversity comes from juvenile stages of coastal taxa, including managed reef fishes. All data to date suggest that the inshore and offshore domains of the Gulf are highly connected. Additionally, the taxa being investigated in this proposal are the primary prey of nearly all cetaceans in the Gulf, as well other oceanic apex predators (e.g., tunas, billfishes). Declines and/or relocation in cetaceans have been putatively linked to changes in prey availability. The proposed research has six primary goals. 1) Develop baseline matrices for the offshore fauna, including spatially explicit abundance estimates using direct sampling and acoustics. These data will be used to quantify spatiotemporal trends, and also inform future natural resource damage assessments, establish prey fields for apex predators, provide juvenile recruitment indices for managed coastal fishes, and eventually, parameterize whole-Gulf models; 2) identify key drivers of offshore assemblages using statistical analysis of biophysical data; 3) develop a long-term ‘indicator species plan’ for investigating abundance, size frequency, petrogenic contamination, and genetic diversity; 4) assemble a compendium faunal inventory of deep-pelagic nekton, including an identification guide; 5) deposit all data in an open-source, freely available, curated database, with exacting metadata annotation; and 6), share activities and findings of the project with stakeholders in the private, education, and industry sectors through a creative and highly successful outreach campaign. The proposal group here comprises internationally recognized leaders in deep-pelagic ecology, taxonomy, field sampling/sensing, biochemistry, population genetics, biophysical statistical analysis, and outreach, paired with Gulf leaders in resource management. The scale and scope of the time series proposed here would be unprecedented