Movement Patterns of Coastal Largemouth Bass in the Mobile-Tensaw River Delta, Alabama: A Multi-approach Study

Largemouth bass (Micropterus salmoides) is a popular recreational sport fish in estuarine environments like the Mobile-Tensaw Delta. However, catch rates of large largemouth bass are often low in these coastal systems. Larger largemouth bass (≥2,268 g) are sometimes thought to move upstream to less saline locations when salinity increases. We combined three approaches to explore movement of adult largemouth bass in relation to salinity and angler displacement: external tagging, acoustic telemetry, and fish releases at tournaments. Movement patterns were more varied at downstream sites than upstream sites. Behaviors of downstream fish included remaining in protected channels near the release location, moving upstream as salinity increased (<2ppt), or moving into the main river channel. Fish upstream generally remained near the release site. Recaptures of largemouth bass tagged externally during regular sampling were typically found in the original tagging site (86%-100% across years), while largemouth bass from a tournament tagging effort dispersed from the release point in <23 days. Effects of angling were observed for each approach, and angler recaptures of tagged fish indicated effects on the largemouth bass fishery including movement of fish to other systems, and the re-distribution of fish from tournament release sites. We found no evidence of broad-scale upstream movement of largemouth bass, particularly when salinity increased in the lower Mobile-Tensaw Delta. Key words: largemouth bass, movement, salinity, acoustic telemetry, external tagging

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