Nassau grouper (Epinephelus striatus, Pisces: Serranidae) movement in the Bahamas, as determined by ultrasonic telemetry

Twenty-two adult (>40 cm TL) Nassau grouper were internally implanted with transmitters and tracked by acoustic telemetry. Methods used to surgically implant transmitters are described. A Nassau grouper implanted with a transmitter and tagged with an external tag for the home-range study was recaptured 185 days later by a fisherman at a known spawning aggregation approximately 220 km from the release point. The step-wise process implemented to identify and define the specific research objectives and appropriate methodology to investigate and determine the home range of a coral-reef fish is described. The two study reefs were characterized and the habitat and prey resource availability were compared. Because numerous divers visually assessed the quantity of available prey at the two reefs, abundance and length estimates were compared to identify potential biases. Area-observation curves plotted for each Nassau grouper revealed that cumulative home-range area increased less than 1% daily between tracking day 5 and day 18. In all cases the observed Nassau grouper movement was more constrained than random. The mean home-range area as determined by 95% MCP for the Nassau grouper was 18,305 m2 ± 4,240 (SE). In all cases, the Nassau groupers at the less structurally complex reef had significantly larger home ranges. Diel activity patterns were investigated by examining the hourly amount of space a Nassau grouper utilized. Nassau groupers are more active diurnally and less active nocturnally. Activity space is influenced by moon phase (full > new), but not by tidal flow (slack = running). This dissertation provides one of the first quantitative determinations of home range for a coral-reef fish. Because Nassau grouper exhibit high site fidelity and have relatively small home ranges, No-take marine reserves (NTMRs) would be an appropriate tool for the protection of the Nassau grouper. NTMRs should be large enough to encompass the maximum home-range area and also provide appropriate habitat. However, providing protection of the daily home-range area is not adequate and additional measures aimed at protecting the Nassau grouper during their long-distance migrations to spawning sites are required.