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Species that periodically and predictably congregate on land or in the sea can be extremely vulnerable to overexploitation. Many coral reef fishes form spawning aggregations that are increasingly the target of fishing. Although serious declines are well known for a few species, the extent of this behavior among fishes and the impacts of aggregation fishing are not appreciated widely. To profile aggregating species globally, establish a baseline for future work, and strengthen the case for protection, we (as members of the Society for the Conservation of Reef Fish Aggregations) developed a global database on the occurrence, history, and management of spawning aggregations. We complemented the database with information from interviews with over 300 fishers in Asia and the western Pacific. Sixty-seven species, mainly commercial, in 9 families aggregate to spawn in the 29 countries or territories considered in the database. Ninety percent of aggregation records were from reef pass channels, promontories, and outer reef-slope drop-offs. Multispecies aggregation sites were common, and spawning seasons of most species typically lasted <3 months. The best-documented species in the database, the Nassau grouper (Epinephelus striatus), has undergone substantial declines in aggregations throughout its range and is now considered threatened. Our findings have important conservation and management implications for aggregating species given that exploitation pressures on them are increasing, there is little effective management, and 79% of those aggregations sufficiently well documented were reported to be in decline. Nonetheless, a few success stories demonstrate the benefits of aggregation management. A major shift in perspective on spawning aggregations of reef fish, from being seen as opportunities for exploitation to acknowledging them as important life-history phenomena in need of management, is urgently needed.

The potential linkages among Cuba and geographically associated northwestern Caribbean locations were examined through simulated transport of snapper larvae for 5 harvested snapper species. The analyses are based on a coupled biophysical model incorporating realistic, intra-annual varying currents from a single year (1984), a Lagrangian stochastic scheme, and larval behaviors to find settlement habitat. Sequential runs centered on peak spawning months and lunar phases estimated the degree to which each spawning event contributes larvae to distant populations or to neighboring populations on the complex Cuban shelf. Results suggest that considerable levels of self-recruitment (ca. 37 to 80% total recruitment) structure Cuban snapper populations, in particular, those from the southern and north-central regions. The northern snapper populations exported larvae to the southern Bahamas, specifically to Cay Sal Bank (ca. 11 to 28% total recruitment), while, for more distant locations, the import of larvae from Cuba was negligible depending on the species. Regional oceanographic regimes for cubera, dog and gray snappers and site utilization (e.g. shelf geomorphology) for mutton snapper caused most within-species recruitment variability. However, a small lag in peak spawning times contributed significantly to high recruitment variability among species. Active virtual larvae stand a better chance of reaching settlement habitat, whereas spatial distribution of recruitment is similar but less structured (i.e. homogeneous low abundance) for passive larvae. This modeling approach produces spatio-temporal predictions of larval pathways with explicit measures of variance. Further, it allows for the quantification of relative levels of connectivity, a component needed in the design of marine reserve networks.

Twenty-one spawning aggregation sites on the Cuban shelf were identified for eight species of snappers (Lutjanus) and groupers (Epinephelus and Mycteroperca) using information from experienced fishers and field studies. Three sites are on the southeastern shelf, eight on the southwest shelf bordering the Golfo de Batabanó, two in the northwest, and eight in the north-central region along the margins of the Archipiélago de Sabana-Camagüey. These numbers may reflect sampling effort as much as absolute aggregation numbers, with most effort concentrated in the southwest and north-central regions. Additional studies, particularly field assessments, are needed to determine the current status and consistency of occurrence of many of these aggregations. Most sites occur near the shelf drop-off at depths of 20-50 m, over reef substrates. Some sites involve sequential use by multiple species over several seasons of the year. Fishing activities have impacted many of these aggregations, both during spawning events and during pre-spawning migrations. This information is being applied in the design of marine reserve networks for several Cuban archipelagos. Intraspecific variations in aggregation formation occur temporally among differing regions of Cuba. Such variations reinforce the need for expanded research efforts on spawning aggregations.