Abstract

This paper provides detailed descriptions of aggregation formation and mass spawning of the Bermuda chub (Kyphosus sectatrix). Spawning coloration and gamete release of K. sectatrix was observed and filmed at the Grammanik Bank, a deep spawning aggregation site used by many different species located on the southern edge of the Puerto Rican shelf 10 km south of St. Thomas, United States Virgin Islands. Underwater visual surveys using technical Nitrox and closed circuit re-breathers were conducted from December 2002 to March 2013 and documented spatial and temporal patterns of movement and aggregation formation along 1.5 km of mesophotic reef. The largest aggregations of K. sectatrix ( > 200 fish) were observed on the Grammanik Bank January to March from 0 to 11 days after the full moon with peak abundance from 60 to 80 days after the winter solstice across all survey years. Aggregation formation of K. sectatrix coincided with the spawning season of Nassau (Epinephelus striatus) and yellowfin (Mycteroperca venenosa) groupers. These spatial and temporal patterns of aggregation formation and spawning suggest that K. sectatrix, an herbivore, may also be a transient aggregating species. On several occasions chubs were observed both pair spawning and mass spawning, and represents the first report of a Kyphosid species aggregating to spawn.

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