Migratory Behavior of Aggregating Male Tiger Grouper (Mycteroperca tigris) in Little Cayman, Cayman Islands

This study, conducted as part of the Grouper Moon Project, reports on the movement patterns and spawning behavior of Tiger Grouper during their reproductive season. Tiger Grouper is one of over 20 species of reef fish that are known to use the western tip of Little Cayman in the Cayman Islands as a spawning ground. This multi-species aggregation is best known for being home to the largest and one of the last known spawning aggregations of Nassau Grouper. Unlike the mass spawning behavior seen with Nassau Grouper, male Tiger Grouper defend territories to attract mates in a lek-like reproductive strategy. Tiger Grouper spawn during winter full moons, typically a few days after the Nassau Grouper. The Grouper Moon research team acoustically tagged ten spawning male Tiger Grouper at the Little Cayman spawning aggregation. Using a hydrophone array surrounding the island, the researchers tracked the movements of the tagged fish for 13 months. The authors observed 3 migratory strategies: resident fish that live at the aggregation site, neighboring fish that live within 4 km of the site, and commuter fish that travel over 4 km for spawning. Fish began aggregating 2 days before the full moon and left the aggregation site 10–12 days after the full moon, from January to May. This research helps shed light on an important, but poorly studied, member of Caribbean coral reef ecosystems. Tiger Grouper reach sexual maturity around two years of age, and live at least nine years. They are protogynous hermaphrodites, meaning they start life as female and then change to male as they get larger. They are largely piscivorous, and play an essential ecological role in structuring coral reef food webs.