Striped eeltail catfish (Plotosus lineatus)

catfish small
Originally uploaded by budak.

In the shallow waters off the Rasa Sentosa Resort, one can quite often see what appears to be a dark clump hovering or moving in the water. Upon closer inspection, the black objects reveals itself to be made up of numerous wriggling little fish. These are juvenile eeltail catfish (Plotosus lineatus) which are marine catfish that grow to about a foot long in adulthood. They are known as eeltail catfish because the caudal or tail fin is seamlessly joined to the dorsal and anal fins to form a single undulating fin that propels the fish. Some eels and the flatfish known as soles also have such joined fins.

The juvenile catfish form a virtual ball that swarms over the reef flat as they wander around seeking both food (probably small crustaceans) and shelter. There doesn't appear to be any 'leader' of the pack but they always move about cohesively and defy any attempt to split the group up.

Don't try to touch the catfish though, even if they are mere inch-long fry. They possess venomous glands in the pectoral and dorsal fin spines that can cause very painful wounds. However, they won't attack or sting unless one is silly enough to handle them.

Plotosus lineatus is probably the only catfish species to be found in coral reefs. It's a wideranging species, found all over the Indo Pacific and Indian Oceans.