Landscape-Scale Movement of Red Drum in a Diverse Estuarine Habitat Mosaic: Can We Really Identify ‘Essential Fish Habitat'?

Rigorous quantitative data on multi-scale habitat utilization by fishes will help stakeholders allocate limited financial and material resources towards the most valuable habitats for promoting healthy stocks. We monitored acoustically tagged red drum (Sciaenops ocellatus) at both broad (40 km²) and fine (sub-meter) scales to track habitat preferences and movement behaviors in a natural, open system. Our data suggest that habitat utilization by fish is highly context dependent, meaning that use of any particular habitat (e.g., oyster reef) is affected by proximity of other habitat types, patch size, diel-to-seasonal cycles, meteorological forcing and social interactions. For instance, oyster reefs adjacent to saltmarsh or seagrass meadows were utilized proportionally more than equally productive oyster reefs on isolated sand flats. At broader scales, our data show that individual relic tidal delta complexes (mosaics of marshes, seagrass beds, oyster reefs and mudflats) separated by 1-2 km are not well connected via the migration of individual fish over monthly timescales. These results provide a more elaborate and fine-scale understanding of the functionality of various habitats as red drum habitat within a dynamic estuarine ecosystem.