Torrent Fish

Blueether, CC BY-SA 3.0, via Wikimedia Commons

Cheimarrichthys fosteri – endemic – is not found in any other country except New Zealand.

Torrent Fish Description

Torrentfish are related to the cod family and look similar.

Torrent fish 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 of the torrent fish are very strong. The pectoral fins are very large and triangular, angled so that water flowing over them presses the fish against the riverbed, helping them to stay in position in fast-flowing water. The pelvic fins are set underneath the head. The dorsal and anal fins have very long bases, 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.

Torrent Fish colouration

All torrentfish have a similar pattern of five dark stripes on a lighter background. This colour pattern camouflages the torrentfish and help it to blend in with its stony habitat.

There are three stripes on the body, generally angled downwards towards the head, with a fourth stripe vertically at the base of the tail and a fifth passing through the eyes and angling downwards towards the base of the pectoral fin. Their colouration is either dark grey on a lighter grey background, or dark brown on a lighter brown background, changing according to the surroundings of the fish.

Torrentfish grow to a maximum of 200 mm in total length, but more commonly reach 100–120 mm.

Torrent Fish life cycle

The torrentfish migrates between the sea and fresh water.

Females migrate downstream over summer and autumn when ready to lay eggs, and return upstream once they have done so.

Looking just like tiny replicas of the adults, juvenile torrentfish enter fresh water in spring and autumn, and after a few weeks in the estuaries, begin moving upstream to the adult habitat. The adults continue to move slowly upstream, with the largest and most inland fish being the females and those in the lower reaches predominately males.

Torrent Fish Habitat

The torrent fish lives in water torrents, the swift white rapids of stony rivers and streams. The torrent fish is not a good climber and only penetrates inland in river systems where the gradient is relatively low. The river system leading to the Tangihua ranges suits them well.

The torrentfish are nocturnal.
During the day they live amongst and beneath loose gravel and stones in the white water and come out at night to feed in calmer water.

picture from Stuff.co.nz environment