The Longfin Batfish can be recognised by the dark blotch below the pectoral fin, and a second elongated dark mark above the origin of the anal fin. Viewed from the side, the body is roughly circular with a low hump on the nape. It is silver, grey or brownish with a dark band through the eye and another level with the pectoral fin.
Juveniles have very long dorsal and anal fins that become relatively shorter as the fish grows.
Adult batfish can grow up to 60cm (24 inches) from the tip of their dorsal fin to the tip of the anal fin.
The species is well known for its highly rounded and compressed body shape. The colour pattern varies widely among individuals. However, various combinations of a light brown or yellowish silver are the most common patterns of colour. There is also a small vertical bar, dark in colour, across the face, and a wider one behind the operculum.
Adults possess highly arched anal fins, and a small bony bulge on the forehead. The juvenile Longfin Batfish are distinctly different in appearance from the adults. They possess a short body, extremely tall anal fins, and display no bulge on the forehead.
The species occurs though much of the tropical Indo-West Pacific.
Longfin Batfish's facts
Longfin Batfish grow extremely fast compared to other fish and quickly reach their full size.
Research has shown they are clever fish and can recognise individual people.
They are very social and form schools with a variety of other species.
They are omnivores and eat algae as well as invertebrates and plankton and pick on corals and anemones.
They congregate on reefs and under floating seaweed, anchored boats are also a favourite hang out spot.
They are unafraid of divers and will often approach them.
The juvenile is very different looking to the adult with a very short body and long dorsal and anal fins.
The juveniles sometimes mimic leaves in the water.
When threatened juveniles can lie down sideways on the bottom to hide and possibly mimic a flatworm.
With their shape they are fast and agile but Longfin Batfish are not strong swimmers.
Longfin Batfish's Behavior & Ecology
Like several other species of fish the longfinned batfish is adapted to survive in numerous environments and can change colour, rapidly shifting between a pale silver to a dark brown, and back when threatened.
The longfinned batfish lives in a variety of environments, from sheltered bays to deep offshore. It has a tendency to form shoals around objects of interest, particularly shipwrecks. Juvenile batfish typically follow drifting debris in the open ocean, but will form groups as they encounter others of the same species.
Longfin Batfish's Feeding
Longfin batfish is an omnivore. It will eat plankton, sessile invertebrates, small invertebrates, and marine algae.
Longfin Batfish habitat
This species inhabits sheltered bays, lagoonal and seaward reefs, and areas around deep offshore reefs and shipwrecks. It occurs solitarily or in small groups, and occasionally forms large schools (Myers 1991, Heemstra 2001). Small juveniles are often associated with floating debris and form aggregations under large Sargassum rafts (Heemstra 2001, Kuiter and Tonozuka 2001). Juveniles also inhabit shallow, protected inner reefs (Myers 1991). The maximum total length is about 65 cm (Heemstra 2001).
Longfin Batfish threats
There are no known major threats. Fishing is not expected to be driving population declines at this time.