Nassau grouper

How it lives

Lives up to about 29 years. Usually alone and territorial on its home reef, then gathers in large groups in winter to spawn around the full moon. In Cayman in 2024 the fish spawned on four nights in a row, starting three nights after the January full moon, and stayed about 10 days before heading home. Adults of spawning age return to the site every year, often more than once in a season.

Where it goes

Mostly stays on its home reef. In winter it travels to a spawning site around the full moon, some fish a few kilometres and others several hundred, then returns home. Acoustic tags showed that the fish at the West End Little Cayman site all live on that island.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

IUCN lists it as Critically Endangered (assessed 2018), after a reported decline of about 60% over 30 years. NOAA says current spawning groups look like a fraction of their historical size, and the US listed it as threatened in 2016. Cayman Islands: four of five historic spawning sites are depleted or dormant, but the West End Little Cayman group grew to more than 8,000 fish in 2023 and nearly 9,000 in 2024, about four times the 2010 count. Cuba: surveys in Jardines de la Reina in 2004 and 2005 found low densities, about 0.48 fish per 1,000 sq m on reef slopes, with no clear difference inside and outside the reserve. I did not find a count for Saint Barthelemy.