Regional abundances of Nassau grouper Epinephelus striatus and yellowfin grouperMycteroperca venenosa have declined due to overfishing of their spawning aggregations, prompting permanent and seasonal fisheries closures in the US Virgin Islands (USVI). As both species produce sounds associated with reproductive behaviors (courtship-associated sounds; CAS), passive acoustic and acoustic telemetry methods were used to determine temporal patterns of reproductive activity, site usage, and fish movements in order to assess the effectiveness of current management strategies at 2 marine protected areas (MPAs) in the USVI: the Grammanik Bank (GB) and Hind Bank Marine Conservation District (MCD). Patterns of sound production and ultrasonic acoustic tag detections showed that both species formed spawning aggregations from January through May at the GB, highlighting the current seasonal regulations (1 February to 30 April) as insufficient for protecting spawning stocks during the entire reproductive season. Acoustic tagging confirmed connectivity between the GB and MCD and exposed the broad extent of habitat used, including non-protected areas, during the spawning season. Spawning did not likely occur within the MCD, but the MPA did support abundances of calling individuals during spawning periods, indicating that both species produce CAS away from their spawning sites. This finding coupled with the detection of routine migrations between spawning and non-spawning sites presents a potential mechanism to lead conspecifics to the aggregation site and thereby increase reproductive fitness and spawning output. KEY WORDS: Nassau grouper • Epinephelus striatus • Yellowfin grouper • Mycteroperca venenosa • Passive acoustics • Ultrasonic acoustic tagging • Fish movement patterns • Marine protected area Resale or republication not permitted without written consent of the publisher

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Sound produced by fish spawning aggregations (FSAs) permits the use of passive acoustic methods to identify the timing and location of spawning. However, difficulties in relating sound levels to abundance have impeded the use of passive acoustics to conduct quantitative assessments of biomass. Here we show that models of measured fish sound production versus independently measured fish density can be generated to estimate abundance and biomass from sound levels at FSAs. We compared sound levels produced by spawning Gulf Corvina (Cynoscion othonopterus) with simultaneous measurements of density from active acoustic surveys in the Colorado River Delta, Mexico. During the formation of FSAs, we estimated peak abundance at 1.53 to 1.55 million fish, which equated to a biomass of 2,133 to 2,145 metric tons. Sound levels ranged from 0.02 to 12,738 Pa2, with larger measurements observed on outgoing tides. The relationship between sound levels and densities was variable across the duration of surveys but stabilized during the peak spawning period after high tide to produce a linear relationship. Our results support the use of active acoustic methods to estimate density, abundance, and biomass of fish at FSAs; using appropriately scaled empirical relationships, sound levels can be used to infer these estimates.