Blue Triggerfish

Pseudoundefinedstes fuscus, commonly known as the blue triggerfish, rippled triggerfish, yellow-spotted triggerfish, or blue-and-gold triggerfish, is a member of the family Balistidae.

Males of Pseudoundefinedstes fuscus can grow up to 55 centimeters (22 inches) in length. The body is predominantly brown, with fins adorned with yellow margins. Juveniles display a yellowish-brown coloration with an intricate network of vibrant bluish wavy lines. As they mature, these lines merge together. This species is notable for its aggressive behavior, leading many divers to exercise caution and keep their distance due to frequent biting incidents.

Pseudoundefinedstes fuscus can be found throughout the Tropical Indo-Pacific region, spanning from the 🌊 Red Sea to 🇿🇦 South Africa, the Society Islands (🇵🇫 French Polynesia), southern 🇯🇵 Japan, 🇦🇺 Australia, and 🇳🇨 New Caledonia (🇫🇷 Overseas France).

Reef-associated, Pseudoundefinedstes fuscus prefers coastal waters, shallow lagoons, and seaward reefs at depths ranging from 1 to 50 meters (3 to 164 feet).

Similar to other triggerfish, Pseudoundefinedstes fuscus feeds on shellfish, small crustaceans, and various bottom-dwelling invertebrates.

Pseudoundefinedstes fuscus demonstrates territorial behavior by actively defending its nesting sites and adjacent areas. This species showcases heightened aggression, especially during the mating season, which commonly occurs in the warmer months, typically in spring and summer. Environmental stimuli, such as increasing water temperatures, serve as triggers during this period, prompting the Blue Triggerfish to adopt a defensive stance. Consequently, it aggressively protects its territory and exhibits confrontational behavior towards perceived intruders as part of its natural response during this reproductive phase.