Greater Amberjack (Seriola dumerili) abundance, distribution and movement in the South Atlantic and Gulf of Mexico regions

Objectives

1. To synthesize bottom habitat observations and construct a spatially explicit habitat model throughout the study area (South Atlantic and Gulf of Mexico).
2. To synthesize existing scientific data and stakeholder knowledge regarding regional, habitat-specific abundance of Greater Amberjack across the study area.
3. To design and conduct a comprehensive study to estimate, within a reasonable margin of uncertainty, the regional, habitat-specific absolute abundance of Greater Amberjack across the study area using a combination of video-based observations (towed, ROV mounted, and stationary) and hydroacoustics.
4. To determine movement behavior and connectivity of Greater Amberjack at local and regional scales using a combination of acoustic telemetry, conventional tagging and genetic markers.
5. To assess the efficacy of environmental DNA methods in conjunction with visual and acoustic approaches to determine presence/absence and/or relative abundance of Greater Amberjack as well as closely related species.
6. To update biological information for Greater Amberjack across the study region (age-length).
7. To engage with stakeholder groups and collaborate with existing outreach teams to facilitate stakeholder input and to communicate the results of the project.
    

Methodology

The approach we propose is highly adaptable and responsive to the results of our synthesis, calibration, and connectivity studies. In a perfect system, we would have a complete understanding of our sampling universe and strata and be able to lay out a detailed a priori design. Unfortunately, comprehensive and high-resolution habitat maps are largely lacking and our knowledge of Greater Amberjack pales in comparison to other fisheries species (e.g. Red Snapper and Gag). Although we lay out the best-informed sampling program (design and approach), we recognize that this plan can and will be better informed by the results of our three-phased approach. Phase I proposed for Fall of 2021 and Spring of 2022 will include the comprehensive data synthesis (Objective 1 & 2), calibration studies (component of Objective 3) and eDNA studies (Objective 5). Phase II (late Spring 2022 -end of 2022) will implement the refined region and habitat observations (Objective 3) using a combination of video based and hydroacoustic surveys. Estimating region- and habitat-specific abundance of GAJ will be achieved by employing both design-based (i.e., stratified random sampling or stratified cluster sampling) and model-based (i.e., hierarchical spatial regression) inference in a unified framework. The final phase (III), Spring to Summer 2023, includes data analysis and stakeholder engagement (Objective 7). Work under objectives 4 (connectivity and movement) and 6 (Biological information) will occur across phase I and II. Finally, our outreach and engagement team will communicate on the projects progress and overall design as well as seek input from stakeholders throughout the project.

Rationale

Management of reef fish in the southeastern United States has become an extremely contentious issue with substantial disagreement in stock status and catch level recommendations among various stakeholder groups. In response to the public concern, the U.S. Congress has appropriated funding for independent studies (the previous Red Snapper count and the current Greater Amberjack count) to estimate an absolute abundance to guide future management and build stakeholder confidence in the underlying science behind fisheries management. The innovative approach we propose to estimate an absolute abundance of Greater Amberjack builds on the success and lessons learned of the Great Red Snapper Count project (GRSC) since many of the scientists included in this proposal were critical to the success of the GRRSC. Estimating an absolute abundance through fisheries-independent sampling has been a long-term goal of fisheries scientists for quite some time. While advance technologies (e.g., ROV based cameras, underwater video systems, hydroacoustics) have greatly improved our ability to estimate local abundance, combining site specific counts within the larger geographic frame of this study to estimate absolute abundance is a daunting task. The lack of high-resolution habitat maps of the expansive study area, the need to understand sampling biases and efficiency of multiple gears that must be used to address regional specific challenges, and the limited understanding of the movement behavior and connectivity of Greater Amberjack are among the most important challenges that must be addressed. We address these challenges by developing a rigorous phased approach that includes (1) Synthesis of existing habitat and fisheries data, (2) calibration of survey methodologies, and (3) region specific surveys stratified by habitat type. We couple this approach with expansive studies of the spatial ecology, connectivity and movement of Greater Amberjack as well as an update of key biological parameters of the species.