Amphiprion cf clarkii “Rowley Shoals”

Common Name: Rowley Shoals Anemonefish

Scientific Name: Amphiprion cf clarkii

Distribution: Rowley Shoals, Western Australia

Type Locality: n/a

Identification: Caudal fin bright yellow in both sexes, but usually NOT obscuring the posterior stripe. Dorsal fin black throughout; ventral fins yellow. Anterior stripe relatively thick and always connected dorsally; medial stripe usually noticeably thinner. Body darkening highly variable in coverage, with some specimens only showing the orange base color near the pectoral fins and others with only the upper back darkened.

Similar: When heavily darkened, almost identical to the Andaman Clark’s Anemonefish, which likely extends as far south as Bali and perhaps further still. The wider medial stripe in that fish is helpful for differentiating, but probably not entirely diagnostic. The Indonesian Clark’s Anemonefish is likewise quite similar, but has a noticeably paler caudal fin, which in males is often margined in a darker yellow.

Notes: Few images of this fish exist, and it seems relatively uncommon within its geographically limited range. This is likely one of the rarest anemonefishes in the world, warranting recognition as an endangered species. Thankfully, its homeland, which presumably stretches as far north as Hibernia Reef, is protected by the Australian Government. None of the other anemonefish species found in this region show any obvious evidence of having speciated, which highlights how prone the clarkii group is to regional endemism.

The islands off Northwest Australia are generally associated with a West Pacific fauna, though the occasional Indian Ocean species does show up. This is similar to Christmas Island in the Eastern Indian Ocean, where geminate species often interbreed and hybridize. The same phenomenon may have given rise to this unique population at the Rowley Shoals. It appears to possess traits of both plausible parent species, for instance, the yellow tail seen in the Indian Ocean and the minimally darkened body often seen in the Coral Triangle.