Torrentfish

The torrentfish, Cheimarrichthys fosteri, is an amphidromous freshwater fish that is endemic to New Zealand. Torrentfish are well adapted to life in shallow, fast-flowing riffles and rapids. They grow to a maximum of 200 mm (7.9 in) in total length, but more commonly reach 100–120 mm (3.9–4.7 in).

Description

Torrentfish are stocky, with a flattened underside, arched back and a broad, downward-tapering head with eyes set high. The lower jaw is very undercut and is surrounded by a fleshy upper lip – an adaptation for picking invertebrates off the surface of stones. The fins are very robust. The pectoral fins are very large and triangular, angled so that water flowing over them depresses the fish against the substrate, helping them to stay in position in fast-flowing water. The pelvic fins are set underneath the head. The dorsal and anal fins are very long-based, with the dorsal fin extending for nearly half of the body length. The tail fin is short and truncated or slightly forked, suited to sudden burst swimming rather than sustained swimming.