We are excited to share a new scientific paper published last month in the journal Environmental Biology of Fishes. This study, conducted by our Grouper Moon Project team, reports on the movement patterns and spawning behavior of Tiger Grouper during their reproductive season, helping to shed light on an important, but poorly studied, member of Caribbean coral reef ecosystems.

Tiger Grouper feed mostly on other fishes, and play an essential ecological role in structuring coral reef food webs. They 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 also one of more than 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 site is best known for being home to the largest and one of the last known spawning aggregations of endangered Nassau Grouper. Tiger Grouper spawn during winter full moons, typically a few days after the Nassau Grouper. Unlike the mass spawning behavior seen with Nassau Grouper, male Tiger Grouper defend territories to attract mates, using a reproductive strategy known as "lekking." Often seen in birds, a lek is an aggregation of males that gather to engage in competitive displays and courtship rituals.

To better understand their movement and behaviors while spawning, 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 three migratory strategies: resident fish that live at the aggregation site, neighboring fish that live within four km of the site, and commuter fish that travel over four km for spawning. Fish began aggregating two days before the full moon and left the aggregation site 10–12 days after the full moon, from January to May.

The full citation of the paper is Sleugh, T., CM McCoy, CV Pattengill-Semmens, BC Johnson, SA Heppell, L Waterhouse, BC Stock, and BX Semmens. 2023. Migratory Behavior of Aggregating Male Tiger Grouper (Mycteroperca tigris) in Little Cayman, Cayman Islands. Environmental Biology of Fishes. doi.org/10.1007/s10641-023-01399-w. To find out more about the Grouper Moon Project, visit www.REEF.org/groupermoonproject. To see all scientific publications that have resulted from REEF's projects, visit www.REEF.org/db/publications.