Movement patterns and water quality preferences of juvenile bull sharks (Carcharhinus leucas) in a Florida estuary

Abstract

Acoustic telemetry was used to examine the size of daily activity space, small-scale movement patterns, and water quality preferences of juvenile bull sharks in the Caloosahatchee River, Florida. Movement pattern analysis included rate of movement, swimming depth, linearity, direction, tidal influence, diel pattern, and correlation with environmental variables. Manual tacking occurred before and after a large freshwater influx which divided the sharks into two groups based on movement patterns. The first group displayed increased rate of movement, distance traveled, and space utilization at night, and movements correlated with salinity, temperature, and dissolved oxygen. The second group had an increased rate of movement, distance traveled, and space utilization during the day, and movements correlated with temperature, dissolved oxygen, turbidity and pH. These juvenile bull sharks displayed distinct diel movement patterns that were influenced by physical factors, which may account for the distribution of this top-level predator in the Caloosahatchee River.