Diamond Leatherjacket

Rudarius excelsus

The Diamond Leatherjacket is a small reef-associated fish found in the Western Pacific, ranging from northern Australia to southern Japan. It reaches a maximum length of 2.5 cm and is known for its extremely small size at maturity, with individuals maturing at just 1.5 cm. The species is characterized by prominently elevated dorsal and ventral profiles and has distinctively long bristles on the caudal peduncle of males, which extend beyond the middle of the caudal fin. Its body shape is short and deep, making it distinguishable from other reef fish. This fish inhabits sheltered coastal habitats, typically in areas with mixed low reef and sparse seagrass. It is commonly found at depths ranging from 8 to 25 meters. The Diamond Leatherjacket is harmless to humans and is not used for any specific human purposes. Divers encountering the Diamond Leatherjacket may find it in shallow, tropical waters, often in the company of seagrass beds. Its conservation status is listed as Least Concern. Observing this fish can be a unique experience due to its small size and distinctive appearance.