This project, funded by the NOAA RESTORE Act Science Program, is a collaborative effort between the University of Southern Mississippi (Frank Hernandez, Kevin Dillon), the University of South Florida (Chuanmin Hu), and the NOAA SEFSC (Pascagoula Lab) (Glenn Zapfe, Walter Ingram).
A major limitation in improving stock assessments for managed species is the general lack of fisheries-independent indices. Currently, few stock assessments include environmental or habitat-related parameters, even though a goal of NOAA Fisheries is to move towards Ecosystem-Based Fisheries Management approaches. Holopelagic Sargassum is a presumed “nursery habitat” for many managed species, yet quantitative (and habit-specific) assessments of nursery function are lacking for Sargassum, and little is known about the environmental and climatic factors that drive variability in Sargassum biomass and distribution.
To evaluate the nursery function and importance of Sargassum to fisheries in a useful context for resource managers, the following objectives will be addressed: 1) quantify Sargassum variability in distribution and biomass at gulf-wide scales in the northern Gulf of Mexico, and understand the environmental controls of such variability; 2) quantify the nursery-role function of Sargassum relative to temporal/spatial variability, habitat morphology, and alternative open water habitats; and 3) develop and test the efficacy of remote sensing and field-derived habitat indices for inclusion in stock assessments of managed species associated with Sargassum.
Objective 1 will be addressed using satellite and field collected data, algorithm refinement, and data synthesis and analysis to: 1) refine remote sensing algorithms to better detect and quantify Sargassum; 2) produce Sargassum distribution maps (monthly means) at coarse (0.5o – 0.2o) and finer (0.05o – 0.01o) resolutions; 3) produce Sargassum biomass abundance maps, similar to the above but in biomass units; 4) enhance the Sargassum Watch System covering the entire Gulf of Mexico for near real-time service; and 5) achieve a better understanding of Sargassum variability by coupling to physical and biological properties in the Gulf of Mexico.
Objective 2 will be addressed using field surveys conducted in Sargassum and open water habitats and lab analyses of collected samples to quantify and compare: 1) habitat attributes identified as being characteristic of nursery areas (e.g., density, growth, condition); 2) patterns in food web structure using gut content analysis, bulk stable isotope, and compound specific stable isotope approaches; and 3) spatial and temporal patterns in the above measures relative to Sargassum biomass and distribution estimates derived from Objective 1.
Objective 3 will be addressed using Sargassum biomass and distribution observations from NOAA SEAMAP surveys and remote sensing observations to: 1) derive ship-based and satellite-based Sargassum habitat indices at multiple spatial and temporal scales; 2) examine relationships between Sargassum indices and recruitment indices for targeted species; and 3) conduct workshops and meetings with stock assessment biologists to incorporate and test the efficacy of Sargassum indices in assessments.
Photos courtesy of Brian Jones.