Grouper source levels and aggregation dynamics inferred from passive acoustic localization at a multispecies spawning...

Area of Science:

• Marine bioacoustics
• Ichthyology
• Animal behavior

Background:

• Four grouper species aggregate and vocalize in Little Cayman, Cayman Islands.
• Traditional observation methods for these aggregations are spatially and temporally limited.
• Passive acoustic localization offers a non-invasive method for long-term, fine-scale monitoring of sound-producing species.

Purpose of the Study:

• To investigate the acoustic behavior of four grouper species (Red Hind, Nassau, Black, and Yellowfin Grouper) at an aggregation site.
• To measure call source levels and analyze spatiotemporal calling patterns using passive acoustic localization.
• To assess the feasibility of using acoustic data for estimating fish density and communication ranges.

Main Methods:

• Deployment of a hydrophone array over a 9-day period in February 2017, coinciding with Nassau Grouper spawning.
• Application of passive acoustic localization to pinpoint the source of grouper vocalizations.
• Measurement of peak-to-peak (PP) call source levels and analysis of temporal calling patterns.

Main Results:

• Yellowfin Grouper exhibited the lowest mean PP call source level, while Nassau Grouper had the highest (143.7 and 155.2 dB re: 1 μPa at 1 m, respectively).
• Nassau Grouper calling peaked after sunset during their spawning days.
• Red Hind calls were most frequent in the afternoon and evening.

Conclusions:

• Passive acoustic localization is effective for studying the vocal behavior of aggregating grouper species.
• Call source levels and temporal patterns provide insights into grouper communication and potential for acoustic density estimation.
• Understanding acoustic behavior is crucial for effective marine conservation and management of grouper populations.