Abstract

Most large groupers form spawning aggregations at predictable locations and times, resulting in their susceptibility to overfishing and other ecological threats. Research, management, and enforcement of such aggregations could be enhanced if their exact locations were known. Traditional detection methods of diver and catch surveys are time consuming, especially when considering multiple species and sites. Many groupers such as red hind, Epinephelus guttatus, are soniferous and increase sound production at specific locations during periods of courtship and spawning, permitting the use of passive acoustics to locate and map these aggregations more efficiently. During January and February 2010 on days and hours known to have high call rates, passive acoustics were used to map a spawning aggregation of red hind off western Puerto Rico. A hydrophone attached to a mobile digital audio recorder was lowered from a boat as the vessel drifted over a suspected spawning aggregation area, while the global positioning system (GPS) coordinates were simultaneously recorded. After listening to the audio recordings, occurrences and intensities of red hind calls were charted with their GPS locations in GIS. The eastern and western boundaries of the aggregation were successfully mapped. The southern and northern boundaries were not defined due to aberrant drift patterns and the end of the spawning period, which resulted in the cessation of red hind calls. Divers confirmed the presence of reproductively active red hind. These time-saving methods and technologies can be expanded to other soniferous groupers, and potentially can be automated so that results can be determined in near-real time.

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