MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14740

ABSTRACT: Fish spawning aggregations (FSAs) may persist for months and include behaviors such as spawning and foraging. Acoustic telemetry has been used to measure movements of fishes to/from FSAs, but behaviors within the aggregation are harder to quantify. We used multi-sensor acoustic telemetry (depth, acceleration) combined with continuous wavelet transformation analysis and hidden Markov models, to identify behaviors within a spawning aggregation of the goliath grouper (Epinephelus itajara), a vulnerable marine predator. Tagged fish (n=20) exhibited periods, over two spawning seasons (August-October), where multiple individuals displayed variability in depth, just after the new moon. These events may represent spawning, and there was always one event each season which included a greater number of individuals and more variability in depth. Grouper were more active during the new moon, in shallow water (< 15 m), and at night. We also identified several events with behaviors more consistent with benthic foraging where grouper were highly active while remaining at constant depth. As such, intensive foraging by multiple individuals may occur during more sporadic time periods. Grouper remained close to the seafloor as currents exceeded 0.4 m sec^-1 but moved up into the water column during cold-water incursions (< 24˚C). As such, abiotic conditions limit vertical habitat use and could potentially influence spawning and foraging behavior. Multi-sensor telemetry combined with time-series analysis can be used to remotely measure individual behavior within spawning aggregations. The timing of these behaviors within the FSA may also have implications for the ecological role groupers play as predators and potentially in bottom-up processes.