Spatial Distribution and Habitat Use of Spawning American Shad in the St. Johns River, Florida

Abstract

American shad Alosa sapidissima populations along the Atlantic Coast of North America are near historic lows despite management actions designed to rebuild stocks. Florida's St. Johns River supports the southernmost population of this anadromous species, and as water use in the St. Johns basin increases, there is concern that their spawning may be affected. We assessed American Shad movement and habitat use in the St. Johns River during three spawning migrations (2009–2011) using acoustic telemetry. Spatial distribution patterns of telemetered shad during each year were largely similar; most shad were located within reaches from Lake Monroe (rkm 276) to just downstream of Lake Harney (rkm 308); some individuals made excursions as far upstream as Lake Poinsett (rkm 386+). Water levels varied among years (low-water level: 2009 and 2011; higher water level: 2010), and lower water levels may have contributed to an apparent constriction of spawning grounds in 2009 and 2011. Telemetered shad selected deeper sections of river with faster currents. Our results verified that the primary spawning grounds for American shad in the St. Johns have not changed substantially in the past 50 years; thus, these areas should rank high for habitat protection. We also demonstrated linkages between American Shad distribution and habitat use and river flow that should be further developed and considered in future water withdrawal, regulation, or conservation efforts. Copyright © 2015 John Wiley & Sons, Ltd.