Abstract

Goliath Grouper populations have shown significant recovery in US waters following the closure of the fishery in 1990; however, despite a higher abundance of adults offshore and juveniles inshore, the extent of the recovery is unknown. Most research efforts to date have focused on adults offshore and their associated spawning aggregations, while less information exists on the juvenile stage that is dependent on mangrove estuaries that function as nursery habitat. We tagged juvenile Goliath Grouper in three south Florida estuaries that differ in their degree of urbanization and environmental conditions starting in 2017 using Vemco acoustic telemetry tags (V9 and V16; 440 days and 6.5 years battery life) to investigate habitat use and movement patterns. We tagged 30 juveniles (size range = 502 - 1132 mm TL) in the St. Lucie River and adjacent Indian River Lagoon; 8 juveniles (216 - 1130 mm TL) in the Caloosahatchee River and Charlotte Harbor; and 22 juveniles (270 - 846 mm TL) in Faka-Union and Pumpkin Bays of the Ten Thousand Islands. Movements by tagged fish within respective estuaries aligned with responses to changes in both salinity and temperature, depending on where the fish was initially tagged. Generally, fish moved out of rivers when freshwater flows increased and returned when salinity increased as flows declined. We also found that the timing of an expected ontogenetic shift to offshore habitat appears to coincide with winter cold fronts. Monitoring fish movements within human-altered systems will help us better understand the patterns in habitat utilization of this iconic species.

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