Mexico

Grouper spawning aggregations in Alacranes Reef, Mexico

Grouper spawning aggregations are under investigation in Alacranes Reef, the largest reef platform in the southern Gulf of Mexico located 140 km off the northern coast of the Yucatan Peninsula, Mexico. Following a protocol that combines the local ecological knowledge of fishers through semi-structured interviews, and verification of reported sites in the field, through diving, the existence of grouper aggregations and sites are indicated on this reef. One example is a spawning aggregation of the “mero del Caribe” (Nassau grouper), Epinephelus striatus, listed as Endangered on the IUCN Red List (http://www.iucnredlist.org/details/7862). According to veteran fishers, Nassau grouper was commonly exploited (using skin diving and speargun) since the 1960s at its aggregations around the full moon of December, January and February at a northeastern site (windward, 20-30 m in depth) of the reef platform. Fishers reported that the aggregation used to consist of up to 4,000 fish, and that sometimes the aggregation entered the reef platform through channels in the reef crest and reached shallow areas (less than 10 m) where fishers were able to “hoop net” groupers from their boats in areas less than 2 m in depth.

In January, February and March 2009, field work was conducted to verify the reported aggregation. Unfortunately, bad weather prevented access to the aggregation site for verification in January. While bad weather prevailed in February and March, inspection of the site was possible on a few days but no Nassau Grouper aggregation was found. In January 2009, three Nassau groupers (not aggregated) were caught by fishers with speargun 12 km south from the aggregation site. While caught groupers were close to the adult size range, their gonads were not mature. Veteran fishers reported that few people have fished the aggregation in the last 15 years.

While it is premature to conclude that a Nassau grouper aggregation was once present and subsequently disappeared from Alacranes Reef, it is clear that the species no longer occupies a significant place in commercial catch. Rather, the red grouper, Epinephelus morio and black grouper, Mycteroperca bonaci are commonly taken.

Fishers also reported an aggregation of the “mero payaso” (red hind - see photo), Epinephelus guttatus at Alacranes Reef. The aggregation site was said to be located north of that indicated for the Nassau grouper. This red hind aggregation was verified by divers, and body sizes and gonad samples taken during January, February and March. According to fishers, other groupers aggregate to spawn in Alacranes Reef, including the Negrillo (black grouper), the Dztoz (tiger grouper), M. tigris, and the Guacamayo (yellowfin grouper), M. venenosa. Their aggregations were reported from the leeward side of the reef platform (14 km away) but were not validated.

Since 1994, Alacranes Reef has been a Natural Protected Area (National Park) but relatively little is known about grouper spawning aggregations in terms of species, sites and threats. Our work, funded by The Nature Conservancy’s Yucatan Coastal and Marine Programme and promoted by Fundación de la Universidad Autónoma de Yucatán, attempts to elucidate the aggregation characteristics for incorporation in the conservation and management programme of the Alacranes Reef National Park.

Alfonso Aguilar-Perera and
Armín Tuz-Sulub
Universidad Autónoma de Yucatán
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