Habitat Use by Telemetered Alabama Shad during the Spawning Migration in the Lower Flint River, Georgia

Abstract

The Alabama Shad Alosa alabamae is an anadromous fish which lives in the northern Gulf of Mexico and ascends freshwater rivers in during springtime to spawn. Populations have experienced substantial range-wide declines due to habitat alteration, including the construction of dams which block access to historical spawning sites. The largest known population of Alabama Shad is found in the Apalachicola River in northwest Florida. To assess movement during the spawning run, 250 Alabama Shad were outfitted with radio and acoustic transmitters and transported from the Apalachicola River upstream to the lower Flint River near Bainbridge, Georgia during 2010-2014. The 153 relocations from 126 individual fish revealed congregation areas that were suspected to be spawning locations. To investigate substrate use by Alabama Shad, relocation data was combined with a detailed substrate map of the lower Flint River to determine whether Alabama Shad were using substrates in proportion to its availability. To assess movement during the spawning run, relocation data was used to determine temporal displacement from the stocking locations during March 15-May 31. Daily river discharge for the lower Flint River for March 15-May 31 2010-2014 was used to determine the timing of large (≥ 20-km) upstream movements in relation to river discharge. Analyses showed that Alabama Shad were selecting for Limerock Boulder substrate, avoiding Limerock Fine and Rocky substrates, and using Sandy substrate in the same proportion as its availability. Alabama Shad upstream movement was greatest during April-mid May, and appeared to be influenced by declining river discharge after periods of high discharge. Movements ≥ 20-km generally occurred during April-mid May and were clustered together over a period of a few days. X-Y coordinates for all Limerock Boulder substrate areas on the lower Flint River were calculated to focus future efforts to determine exact spawning locations of Alabama Shad on the lower Flint River. Future telemetry efforts on the lower Flint River and elsewhere should collected water temperature data reliably in order to investigate the possible interactions between water temperature and river discharge that influence Alabama Shad behavior during the spawning migration. Icthyoplankton sampling conducted in the vicinity of Limerock Boulder substrates, combined with boat electrofishing, during periods of declining river discharge April-mid-May is recommended as a sampling approach for identifying exact spawning locations for Alabama Shad in the lower Flint River. The development of a Habitat Suitability Index for Alabama Shad using flow, depth, temperature and substrate measurements from identified spawning locations will aid in locating additional spawning locations on the lower Flint River and in other drainages where this species still persists.