In the Water: Fishes

Nassau grouper

Epinephelus striatus

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About

Nassau groupers are a common sight on every Saba dive, but their large numbers around Saba are incredibly special compared to elsewhere. These critically endangered fish grow to over 1 m/3 feet in length and can live up to 30 years, usually reaching maturity at the age of 4 or 5. These fish used to be one of the more-common grouper species, but their large size (and behavior of gathering in massive groups during spawning events) have made them easy targets for over-fishing.

These big fish aren’t picky eaters — they’re ambush predators, primarily letting their prey come to them (and taking full advantage of low-light hours at dawn and dusk). When an unsuspecting fish crosses paths with a hungry adult Nassau grouper, the grouper will swallow it whole, using powerful suction created by their large mouths.

Nassau grouper spawning events are, to put it mildly, magnificent: They gather in hundreds, thousands, or even tens of thousands intermittently between November and February, under the light of the full moon when the water temperature is just right. Courtship happens in a dance of changing color-patterns and synchronous movement, always in the same sites, year after year. To help their populations continue to recover, harvesting restrictions have been put in place at many of these sites, especially during active spawning season. In the Saba Marine Park, such restrictions have contributed to local Nassau grouper populations flourishing.

Outside of spawning events, adult Nassau groupers are actually relatively solitary, spending most of their time along coral reefs or rocks. While these fish remain critically endangered for now, continued protections from overharvesting (along with scientific research aimed at better understanding their reproduction cycles) can make an impact. If you spot one while diving, be sure to snap a photo and upload it to iNaturalist, where your observations provide critical data for scientists and decision-makers working to protect these incredible fish.

Header image of a Nassau grouper spawning event in Belize courtesy USAID Biodiversity & Forestry.

This species is:
Native

Why that matters:
Native species are those that evolved in the region naturally, without human influence. That means they’re specifically adapted to Saba’s habitat, and play a key role in island biodiversity. When we lose native species, gaps appear in the ecosystem. That leads to cascades of additional extinctions, and to the loss of the ecosystem services (food, clean air and water, flood and coastal protections, and more) that we humans rely on.

Credit: Kerry Lewis (unknown location), iNaturalist (CC-BY-NC).

iNaturalist Observations

Nassau grouper

iNaturalist user @djscho (CC-BY)

iNaturalist user @neild (CC-BY-NC)

Where locals, researchers, and visitors have seen this species.

Saba Island Map and Pins: iNat Taxonomy ID 49746

This map shows geotagged observations of this species made on iNaturalist, the world’s largest community-science platform.

iNat depends on people like you. By uploading photos of species you see in the wild, you can easily learn more about them — while also contributing critical data used by scientists and conservation-managers around the globe.

See something odd?

Observations of land species in water:
Connectivity can affect how accurate location services are, and in the case of endangered species, location is often automatically obscured.
Missing observations:
Your help is needed to collect more data for this species!

Ask a Scientist

Question: We hear a lot about the threats facing coral reefs: bleaching, ocean acidification, etc. What gives you hope, as a scientist?

Answer: Coral reefs are experiencing unprecedented rates of decline. Facing these kinds of realities — recognizing that right now, the only real solution to this at a global scale is mitigating climate change and cutting carbon emissions as quickly as possible — the thing that gives me the most hope is that there have been palpable changes in the scientific community over the last eight or so years in the ways that people are thinking, and the types of work people are trying to do. It’s incredibly inspiring. We haven’t found a solution yet, but we’re on the right track.

Dr. Rebecca Albright
Curator of Invertebrate Zoology & Geology, California Academy of Sciences