Marine Wildlife Encyclopedia
Banded Butterflyfish Chaetodon striatus
Species: Chaetodon striatus
Species ID: C.CS
Description: A small, disc-shaped fish with a pointed snout and prominent spines at the leading edge of the dorsal fin. The body is pale silver or white, with a thin black vertical bar running through the eye and two thicker vertical body bars . The fins at the rear of the body are black and edged in white. Sexes appear similar and juveniles resemble adults with a large black spot, ringed in white, at the back of the dorsal fin
Maximum Size: 16 cm (6 in)
Longevity: Unknown, but likely to be about 10 years based on the longevity of close relatives
Status: Not currently on the IUCN endangered species list
Banded Butterflyfish & People: This species is not fished for food, but is often collected for export in the aquarium trade
Geographical Range: Found throughout shallow waters of the Caribbean, North to New Jersey, and South to Brazil
Coral Reef Zone: Found primarily in the back reef and fore reef zones
Favourite Habitat: Banded butterflyfish spend their time over reefs or rocky bottoms that offer plenty of shelter
Depth Range: 3–20 m (10–60 ft)
A Day in the Life:
Dawn: Fish emerge from night-time shelters and become increasingly active
Day: Banded butterflyfish roam shallow reef areas in search of food
Dusk: Spawning occurs in deeper water just after sunset
Night: Banded butterflyfish find shelter from nocturnal predators within reef crevices
Who Eats Who
The banded butterflyfish is a carnivore that specializes in feeding on marine worms, known as polychaetes, but will also nibble on zoanthids, anemones, and various eggs. Banded butterflyfish easily outmanoeuvre most diurnal predators and are vulnerable mainly to nocturnal predators such as moray eels, large carnivorous fish and sharks.
Scuba Diver & Snorkeler Best Practices
Participate in scientific underwater assessment projects: Science matters—advanced snorkelers may wish to participate in fish or coral censuses. Assessments such as these help scientists and marine managers take ‘the pulse’ of coral reefs. Not only will you experience the pleasure of snorkeling, but you will also know that you are helping advance knowledge of the ecosystem and aiding in its protection.
Banded butterflyfish generally ignore divers and snorkelers but will move away if closely approached; use the reef structure as cover, or wait until the butterflyfish moves towards you.
Banded butterflyfish are carnivores that actively forage throughout the day for invertebrates. They scan the bottom for worms and attack their exposed feathery gills or other extremities. They are also fond of zoanthids – colonial invertebrates that resemble flattened anemones. During coral spawning events, banded butterflyfish stay up late to benefit from the rare treat of fatty and nutritious egg bundles released by corals into the water column at night. Occasionally, members of this species act as cleaner fish and remove parasites from other coral reef organisms.
Observe, record & share:
O C.CS-101 – Feeding on invertebrates: Banded butterflyfish nip at the exposed parts of freeliving worms, tube worms, and zoanthids
O C.CS-102 – Feeding on coral spawn: Butterflyfish gobble the egg bundles released from corals at night
O C.CS-103 – Cleaner fish: This species occasionally picks parasites from other organisms
Attack & Defense Behaviour
Banded butterflyfish are very agile, as their narrow bodies make them highly manoeuvreable. When faced with a threat, their first instinct is to flee and look for shelter. If trapped against the reef, banded butterflyfish adopt a defensive pose and face the threat while tilting the body forward and raising the dorsal spines. These butterflyfish defend a territory jointly with their mate, mainly in order to guard their mate against wandering bachelors and bachelorettes. When faced with an intruder, butterflyfish will give chase. If the threat persists, they may swim parallel to the intruder, comparing body size and signaling aggression. When feeding on plankton above the reef – a rare strategy used when their usual benthic food becomes scarce – banded butterflyfish may school for added protection.
Observe, record & share:
O C.CS-201 – Escape: Banded butterflyfish flee and look for shelter
O C.CS-202 – Defensive pose: A cornered banded butterflyfish may face the threat with their spines erect and body tilted forward
O C.CS-203 – Chase and parallel swimming: Banded butterflyfish chase intruding butterflyfish or swim rapidly alongside them to signal aggression
O C.CS-204 – Schooling: Banded butterflyfish gather in small groups to feed above the reef
Banded butterflyfish reproduce sexually by broadcast spawning and do not undergo sex change during their reproductive development. Banded butterflyfish are often seen wandering the reef in monogamous pairs. During the breeding season, courtship begins at dusk when the male swims just ahead of the female using exaggerated fluttering motions. The female rises above the male and he responds by dropping back behind her, nosing her tail fin and her belly, and tilting his body forward. The pair then rises slowly up into the water column before simultaneously releasing a white cloud of gametes before heading back to the reef. Pairs often make several “practice” runs, known as false starts, before actually releasing their eggs and sperm. The breeding season of the banded butterflyfish runs from February to April, with some fish spawning several times throughout this period.
Observe, record & share:
O C.CS-301 – Male fluttering: Males swim in an exaggerated fluttering style in front of females
O C.CS-302 – Male nosing: Males press their snout against the female’s belly
O C.CS-303 – False start: Couples begin to rise above the reef but stop prematurely and start over
O C.CS-304 – Spawning: Couples slowly rise high above the reef and release a cloud of gametes
Feeding on invertebrates: Banded butterflyfish love to eat marine worms, known as polychaetes, and other small invertebrates which are very good at staying hidden either within protective tubes or inside crevices in the reef. The narrow body and pointed snout of the banded butterflyfish and its relatives allow it to get into tight spaces and pick its elusive prey from every nook and cranny. Furthermore, the banded butterflyfish has ten rows of bristly teeth that allow it to grasp even the most slippery prey.
Did You Know?
• The dark band across the eyes of this and other butterflyfish species is thought to disguise the position of the head from predators, which often orient their attack towards the eye of a fish. A bite to the rear, although painful, is easier to survive than a bite to the head.
• Depending on where you are, you might hear banded butterflyfish referred to as the Portuguese butterfly (Cuba), banded mariposa (Cuba), butterbun (Jamaica), and even school mistress (Barbados).
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)