Abstract

When groupers or other species gather at transient spawning aggregations, fisher scientists can efficiently collect data needed for sustainable management. Measures of fecundity, spawning frequency, harem size, sex ratio, and site fidelity all provide insights into the life history traits of the species. Spawner numbers and sizes can provide indices of abundance for the dispersed population. Changes in abundance, sizes or sex ratio can indicate intensity of fishing pressure. However, aggregated fish can also be more easily overexploitation than when dispersed at their home reefs. Although spawning aggregations have been fished historically, many of these sites are still unknown to scientists and managers and, therefore, are unavailable for research, monitoring and management. We have developed a low-tech approach to map the extent of known spawning aggregations and to identify previously unknown spawning sites. We deploy an array of drifters equipped with sound recorders to listen for the species-specific sounds of grouper courtship and spawning. Analyses of sound pressure levels and species-specific courtship calls from explorations off western and northeastern Puerto Rico have provided spatial definition for the red hind aggregation site at Abrir la Sierra (ALS) and have detected likely locations of undocumented fish spawning aggregation sites on the shelf near ALS and the shelf north of Culebra. Confirmation and monitoring of these newly identified aggregations provide new opportunities to understand and manage these valuable natural resources.

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