Fish-Nursery Use in Georgia Salt-Marsh Estuaries: The Influence of Springtime Freshwater Conditions

Abstract

The fish assemblage using shallow nursery habitats in the Ogeechee River-Ossabaw Sound salt-marsh estuary, Georgia, was investigated during the winter and spring of two successive years. High river discharges during these periods produced fully freshwater conditions (all tidal stages and amplitudes) in the upper portion of the study area for up to 4 months. Abundances of Atlantic croaker Micropogonias undulatus, southern flounder Paralichthys lethostigma, silver perch Bairdiella chrysoura, and hogchoker Trinectes maculatus recruits were highest in the upper estuary. Spots Leiostomus xanthurus were more evenly distributed, but continued to use upper-estuary nursery areas during periods of high river discharge. Although the recruitment of several species likely was inhibited during discharge peaks, only striped mullet Mugil cephalus avoided freshwater conditions. Spots, southern flounder, Atlantic menhaden, and silver perch utilized shallow nursery areas on a size-specific basis. Recruitment and utilization patterns of fishes spawned in deeper areas generally were maintained throughout prolonged periods (up to 100 days) of freshwater conditions. The precise function of upper-estuary nursery areas is governed by the timing and magnitude of discharge events, but remains essentially intact through the seasonal encroachment of fresh water. Received June 9, 1983 Accepted May 15, 1984