Mottled Spinefoot (Juvenile)
Siganus fuscescens
Type: saltwater, reef fish, benthic
Physical Characteristics
Oval, compressed body with a small mouth. Juvenile coloration includes a mottled brown and cream pattern for camouflage. Known for having 13 dorsal spines, 7 anal spines, and 2 pelvic spines, all of which are venomous. The tail is slightly forked.
Habitat & Distribution
Found in shallow coastal waters, rocky reefs, sea grass beds, and estuaries throughout the Indo-West Pacific, from southern Japan to Australia.
Size & Weight
Juveniles are often only a few centimeters long; adults typically reach 20-25 cm, with a maximum length of 40 cm and weight around 0.5-0.8 kg.
Similar Looking Species
White-spotted Spinefoot (Siganus canaliculatus), which has more distinct, smaller white spots and different gill raker counts.
Ecological Role
Primarily a herbivore that controls macroalgae growth on coral reefs and rocky substrates, preventing algae from overgrowing coral.
Diet
Herbivorous grazer, feeding mainly on benthic algae and seagrasses. Juveniles may occasionally consume small invertebrates found within the algae.
Behavior
Juveniles often form large, dense schools in shallow water for protection, moving into deeper reef areas as they mature. They are primarily diurnal.
Reproduction
Gonochoric. Spawning often follows lunar cycles, with large aggregations of adults migrating to specific reef edges to release pelagic eggs.
Conservation Status
Least Concern (IUCN); populations are widespread and stable in most regions.
Identification Tips
Look for the characteristic 'rabbit-like' mouth profile and the distinct arrangement of numerous venomous spines on the dorsal and anal fins. Juveniles exhibit a blotchy, mottled camouflage.
Interesting Facts
These fish are called spinefoots because of their unique pelvic fins, which have a spine on both the inner and outer edges. The venomous spines can cause painful stings if handled.
Identified on: 5/20/2026
Mode: Standard