Marine Wildlife Encyclopedia
Barred Hamlet Hypoplectrus puella
Species ID: S.HP
Description: A small, disc-shaped fish with rounded fins, a sloping forehead and pointed snout. The body is covered in wide, brown bars against a pale background, and the snout and eyes are adorned with bright blue lines and spots. Juveniles are cream coloured with characteristic black and white blotches at the base of the tail. Scientists believe that the different types of hamlets that exist are actually a single species exhibiting identical behaviours. This booklet will focus on the barred hamlet, which is arguably the most common, but the information contained here is also applicable to other hamlet types
Maximum Size: 15 cm (6 in)
Status: Not currently on the IUCN endangered species list
Barred Hamlets & People: Hamlets are relatively unimportant in commercial fisheries and the aquarium trade
Geographical Range: Barred hamlets are found throughout the Caribbean
Coral Reef Zone: Hamlets are found at moderate depths in the back reef and fore reef zones
Favourite Habitat: Hamlets prefer complex, rocky reef areas with plenty of hiding spots
Depth Range: 3–23 m (10–75 ft)
A Day in the Life
Dawn: Hamlets emerge form their shelters and make their way to feeding grounds
Day: Hamlets search for food and defend their territories against other hamlets
Dusk: Hamlets migrate to the reef slope or drop-off zone to spawn
Night: Hamlets seek shelter within the reef for the night
Who Eats Who
Hamlets in general are carnivores that specialize in feeding on crustaceans such as crabs and shrimp, and only occasionally eat fishes. Hamlets are consumed by a wide variety of coral reef predators, most notably grouper, snappers and jacks.
Scuba Diver & Snorkeler Best Practices
Master neutral buoyancy: Practice neutral buoyancy while maintaining a comfortable distance from the coral reef at all times; this is not just for the sake of the reef, but also for your own safety. Perfecting neutral buoyancy will make you more comfortable while diving, help maximize your air consumption and allows you to get the most from each and every dive.
Hamlets are curious little fish that are easy to approach with slow, non-threatening movements – although if startled they immediately dash to the nearest shelter.
Barred hamlets are carnivores that actively hunt for food during the day. Hamlets specialize in feeding on small crustaceans, such as shrimp, and comb the reef for prey which they capture using a lightning-fast strike. Hamlets sometimes follow behind schools of grazing fishes, such as parrotfishes, in order to pick off the animals that are flushed out of the reef as they pass. If they come across a school of tiny mysid shrimp, hamlets will rush through the school with an open mouth to capture them.
Observe, record & share:
O S.HP-101 – Feeding strike: Hamlets fixate on prey and execute a lightening-fast strike
O S.HP-102 – Shadow feeding: Hamlets follow schools of grazing fishes in order to attack prey flushed out of hiding
O S.HP-103 – Feeding on mysid shrimp: Hamlets rush through clouds of mysid shrimp with open mouths
Attack & Defense Behaviour
Barred hamlets are fiercely territorial and use a wide range of aggressive signals to defend their feeding areas from other hamlets. Smaller opponents can usually be driven away with a quick chase, but evenly matched hamlets often engage in a drawn-out, ritualized duel. Contests begin with rivals making short rushes at each other. If neither fish relents, the hamlets face-off by spreading their fins, tilting their bodies forward and presenting their broad side while twitching the head and beating the tail. If this does not settle the dispute, the fish become more aggressive and may charge their opponent. The target of a charge will often roll onto its side in defence so that the attacker is met with raised dorsal spines. Finally, hamlets may also approach each other, hovering cheek-to cheek, then suddenly snap the head sideways to bite the opponent’s head and snout.
Observe, record & share:
O S.HP-201 – Short rushes: Two rivals take turns rushing at each other
O S.HP-202 – Aggressive display: Hamlets spread their fins, tilt forward and present their flank while twitching their head and tail
O S.HP-203 – Charge: One hamlet rushes at and collides with another
O S.HP-204 – Dorsal fin roll: One hamlet rolls onto its side and raises the dorsal spines
O S.HP-205 – Head alignment: Opponents face each other, hovering cheek-to-cheek
O S.HP-206 – Biting: Opponents lunge at each other, biting the head and snout
Barred hamlets reproduce sexually by broadcast spawning. They are one of the few fish species that are simultaneous hermaphrodites, meaning they have both male and female reproductive organs and can use them interchangeably; however, they cannot self-fertilize. To maximize their reproductive success, hamlet pairs take turns as either the male or female so that each hamlet has a chance to release eggs and to fertilize eggs in a practice known as egg-trading. Hamlet spawning occurs in the few hours before sunset, and takes place at coral outcroppings on reef slopes or near drop-offs. Hamlets pair up, usually with a habitual partner. Courtship is a mutual affair, and both partners take turns chasing each other, spreading their fins, snapping the head from side to side, and tilting and quivering. The courtship ritual’s primary aim is showing off the belly, which is swollen with eggs during this time. When the pair is ready to spawn, they may pale before briefly rising together above the reef, intertwining and releasing gametes. In general, hamlets spawn almost every night, year round.
Observe, record & share:
O S.HP-301 – Pair: Pairs form just before sunset, prior to spawning
O S.HP 302 – Courtship display: Hamlets chase each other, spread their fins, snap their head from side to side, and tilt and quiver
O S.HP-303 – Blanching: Hamlets often pale just before spawning
O S.HP-304 – Spawning clasp: Hamlets rise above the reef and intertwine their bodies
O S.HP-305 – Spawning: While in the spawning clasp, the fish tremble and release gametes
Spawning clasp: Hamlet spawning behaviour is one of the loveliest to witness. After the members of a pair take turns courting each other, the fish acting as the female rises above the reef and bends her body into a shallow S shape. The partner follows, wrapping his body around hers. The fish press against each other while curling their tails around the nape of their partner’s neck in what resembles a passionate embrace. Just before spawning, the fish rotate slightly and tense up, often flexing their jaws so that they jut out, before trembling and releasing a cloud of gametes into the space between their bodies. The pair can spawn up to 10 times before running out of eggs and sperm, and each time they spawn they reverse sexual roles. Because these fish spawn so frequently and scarcely notice an audience, hamlets provide an excellent opportunity for divers and snorkelers to witness fish reproduction in action.
Did You Know?
• There are many types of hamlet, but scientists believe they are all just once species. Each hamlet type can breed with each other, and hybrids with colour patterns intermediate between those of their parents are a relatively common sight on coral reefs.
• During courtship and spawning, hamlets produce various sounds by vibrating muscles attached to the swim bladder, although these sounds are difficult for divers to hear underwater.
• In some cases, spawning is preceded by overtly aggressive behaviour, suggesting that some hamlets may actually bully a partner into spawning.
What to do?
Share your observations today!: Discover your species of interest, observe its behaviour, and share your pictures and videos with friends and coral reef enthusiasts around the world! Upload media to the web, tagged with species common name (ex.: trumpetfish) and species ID code (ex.: A.AM) or species behaviour code (ex.: A.AM-101)