Habitat Use and Connectivity of Juvenile Red Drum and Spotted Seatrout Across Estuarine Seascapes

Abstract

Red drum (Sciaenops ocellatus) and spotted seatrout (Cynoscion nebulosus) are important gamefish that co-occur in estuarine seascapes throughout their range and support recreational fisheries of considerable economic value. Management of these species is compromised by knowledge gaps regarding habitat use and connectivity of late juveniles at multiple spatial scales. Thus, habitat-scale (~1 m to 1 km) and bay-scale (~1 to 50+ km) tracking was conducted using acoustic telemetry in an estuarine system on the coast of Texas, including a large portion of the Mission-Aransas National Estuarine Research Reserve (MANERR) and associated waters. Habitat-scale tracking was conducted for one month using an acoustic positioning system consisting of 20 acoustic receivers, which triangulated fish position with high spatial resolution. Bay-scale tracking occurred over a two year period and employed 45 acoustic receivers placed in several bays and two tidal passes.

Habitat-scale tracking revealed that seagrass was used extensively by each species, and red drum were also associated with oyster reef and boundaries between habitat types. Habitat partitioning was observed as spatial overlap between the two species was limited, with red drum commonly observed in shallower water depths than spotted seatrout. Diel shifts in habitat use and rate of movement were documented for each species and possibly linked to shifts in foraging activity. Bay-scale tracking primarily revealed restricted movement within bays, and final displacement of both species was typically less than 5 km. Directed bay-scale movement was greatest in winter and spring for both species, when a small contingent of individuals made directed movements of up to 70 km. Results of the study indicate that habitat use and movement were species-specific and subject to temporal variation, both diel and seasonal. Habitat-scale connectivity was influenced by seascape structure and water depth, and bay-scale connectivity was generally limited, suggesting that the sustainability of these fisheries is tied to local conditions.