Spotted oceanic triggerfish

Appearance

The maximum length for this species is 50 centimetres but usually grows up to 35 centimetres. Adults and juveniles have different coloration. Adults are blue grayish while juveniles are grayish black with white spots that fade over age. Adults may be seen with dark blotches appearing on the face and pectoral fins during mating.

These dark markings are also present on females hovering above their nests and may disappear within a few seconds once they ascend upwards in the water column, away from their nest. In this fish, the dorsal and anal fins are curved on the back. The dorsal fin of this species has from 23 to 27 rays.

The first dorsal fin’s rays are spinous, with the first two rays more like sharp thorns. The smaller second thorn props up the longer first thorn giving it the appearance of a trigger, after which the fish is named. Its anal fin has 20 to 27 rays. Adults and juveniles also have different caudal fin shapes. Juveniles have rounded caudal fins and adults have concave ones.

Distribution

It range in the western Pacific Ocean ranges from the Gulf of Thailand north to the Yellow Sea and Japan. The range in the Pacific Ocean extends to the Philippines, Indonesia, and all the way to Polynesia and Hawaii.

In the eastern Pacific Ocean, They are found from Mexico and around the Gulf of California down to Peru and the Galapagos Islands. Around the Indian Ocean, it ranges from the Red Sea and eastern Africa to Seychelles, the Maldives, the Persian Gulf, India, Sri Lanka, the Andaman Sea, Australia, and Indonesia.

Populations in the Atlantic Ocean range from New York down to the Gulf of Mexico, the Bahamas, the Caribbean Sea and down to Brazil in the western side. Around the eastern Atlantic Ocean, it ranges from the British Isles and the Bay of Biscay to Azores, the Canary Islands and western Africa. Some populations are also found in South Africa. The spotted oceanic triggerfish inhabits warm waters high in biodiversity, characterized by strong surface currents and upwelling systems . It can be found on deep slopes right offshore, open water and under fish aggregating devices where they have been seen in groups of hundreds or thousands.

Status

The worldwide populations of ''Canthidermis maculata'' are considered stable and the IUCN considers this species of the conservation status: least concern.

Behavior

''Canthidermis maculata'' are known to gather in large groups, hundreds and sometimes thousands and are frequently associated with FADs. These aggregations may also include other species such as the sleek unicorn surgeonfish, Naso hexacanthus.

Oceanic triggerfish are currently thought to move as a group, migrating together from the open ocean to shallower waters for nesting purposes, and returning together to the open ocean once nesting is complete. They are typically nonaggressive, shy, and easily scared away from their nests when confronted by bigger fish such as the titan triggerfish, and divers.

It is likely, due to diver observations of courtship patterns, that only female oceanic triggerfish exhibit nest guarding behaviors and though easily scared away by larger fish, will defend their nest from smaller carnivorous fish such as goatfish and wrasse.

Reproduction

Adults pair up and breed.

''Canthidermis maculata'' nesting is unlikely to be impacted by lunar cycle and has been determined to occur year-round. Eggs are deposited in sand and/or coral rubble, shallowly buried beneath the sand, and are both aerated and guarded by the mother. Frequently, many nests are located near one another, supporting the idea that these triggerfish nest as a group. It is unclear how often a female nests per year and whether or not it returns to the same nest or builds new nests in its habitat range. Additionally, nests have been found at depths ranging from 4 meters to over 45 meters, with the deeper nests being considered a defensive strategy against titan triggerfish which nest at shallower depths and are known to be territorial when nesting .

Food

Spotted oceanic triggerfish display plasticity in their eating habits, being considered either a carnivorous or a planktivorous fish. Upon examination, they consume smaller fish, Halobates , members of the order “Siphonophores,” and smaller cartilaginous fish.