Meet our October Fish of the Month, the Blue Hamlet, Hypoplectrus gemma — a shimmering, all-blue jewel of the reef and one of the Florida Keys’ true local specialties. Found almost nowhere else on Earth, it is a fitting star for October, when REEF Fest brings our community together in Key Largo.

Survey Regions: Blue Hamlets belong to the Tropical Western Atlantic (TWA) survey region, with a stronghold in Florida and especially the Florida Keys. REEF surveyors log them most reliably here, which makes every sighting a point of pride for Keys divers.

Size: Small. Typically around 8 to 13 cm (3 to 5 in), with the deep, laterally compressed body of a miniature sea bass.

Identifying Features: The Blue Hamlet is unmistakable among Atlantic reef fish: a uniform, iridescent pale blue body with no bars or blotches, set off by fine dark speckling around the snout and eyes. That solid blue color separates it from its many hamlet cousins, which wear stripes, bars, and patches of contrasting color.

Fun Facts: Hamlets are one of the reef’s great evolutionary puzzles. The genus Hypoplectrus includes more than a dozen color forms, among them the Blue, Indigo, Barred, Butter, Shy, and rare Golden Hamlet, that are nearly identical in every way except color. Scientists still debate whether they represent many species or one. Hamlets are also simultaneous hermaphrodites: each fish carries both male and female organs, and spawning pairs take turns releasing eggs and sperm in a remarkable dusk ritual known as “egg trading.”

Hamlets hold a special place in REEF’s story, too. Our Golden Hamlet Club, which honors volunteers who complete 1,000 or more surveys, is named for the elusive Golden Hamlet, a nod to how rewarding it is to spot every member of this colorful family. This month’s photograph comes from the late Paul Humann, a REEF Co-Founder whose fish identification books and images introduced generations of divers to the underwater world.

See the Blue Hamlet in the wild. There is no better place to look than right here in the Florida Keys. Join us for REEF Fest, October 15–18 in Key Largo, and dive the very reefs this Keys specialty calls home. Most events are free, but pre-registration is requested. Learn more and register at www.REEF.org/REEFfest.