About Balistapus undulatus (Park, 1797)
The orange-lined triggerfish, Balistapus undulatus, has a dark brown to dark green body marked with orange lines that begin behind the head and cover the entire body. It reaches a maximum body length of around 30 centimeters. The species has a stocky, oval-shaped body that is compressed laterally. Its large head makes up about one third of its total body length. The small mouth is positioned at the front of the head, and the fish has strong teeth. The first dorsal fin holds three spines, one of which is longer and stronger than the other two; this spine can be erected, and is held in a dorsal furrow when the fish is at rest. The second dorsal fin matches the anal fin in shape and size, and the anal fin sits symmetrically opposite the second dorsal fin. The pelvic fin is reduced to a small ventral protrusion. Orange-lined triggerfish usually have a large black spot near their peduncular spines, and their caudal fin is orange. Mature males are generally larger, lack a concave snout, and lose the orange lines on their snouts as they mature. Females and juveniles are smaller and have a concave snout. This triggerfish species is found in coral reef ecosystems, coral lagoons, and external reef slopes across the Indo-western Pacific, including waters off the coast of East Africa, the Red Sea, and Japan, where other balistoid fishes like filefish and leatherjacks also occur across the broader region. Individuals typically remain close to their burrows and dens within reef structures. Compared to other triggerfish species, the orange-lined triggerfish is more versatile in its habitat use within coral reefs. It can be found at depths as great as 50 meters, though it prefers depths between 2 and 8 meters. No link between reef area and depth has been observed for juveniles, while adult depth ranges vary by region, and the species overall has a broad distribution across reefs. Adults and juveniles also prefer different substrate types: adults favor rock and branching coral, while juveniles prefer softer surfaces.
