Giant kokopu

For the general article about kokopu, see kokopu.
Giant kokopu
Giant Kokopu
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Osmeriformes
Family: Galaxiidae
Subfamily: Galaxiinae
Genus: Galaxias
Species: G. argenteus
Binomial name
Galaxias argenteus
(J. F. Gmelin, 1789)

The giant kokopu (Galaxias argenteus) is a species of anadromous ray-finned fish in the genus Galaxias, found only in New Zealand. It grows to a length of up to 45 cm, and is the largest member of the Galaxiidae family. It is mostly a marine species living around the coasts, but it is also one of the five species that join in the whitebait runs that enter New Zealand rivers each spring. Due to the large size of the giant kokopu, it is the only galaxiid species likely to be able to outcompete trout, and as such, the presence of G. argentenus could add to a stream's resistance to brown trout invasion.[2]

The giant kokopu has a single dorsal fin and anal fin, both of which are large, rounded, and set back close to the large square caudal fin. The pelvic fins are also large. Like all galaxiids, this fish lacks scales and has a thick, leathery skin covered with mucus. It is a golden-brown colour with the dorsal surface and flanks speckled with numerous ochre spots. Although it can grow to a length of 45 cm (18 in), a more common size is 20 to 30 cm (8 to 12 in).[3]

Behaviour

The giant kokopu is primarily a coastal species and enters rivers in spring, but it has never actually been observed spawning and little is known of its reproductive biology. Some fish exist permanently in land-locked stream systems. When in fresh water, they prefer slow-flowing waters in lowland runs and pools. They usually use cover such as overhanging vegetation, logs, undercut banks, or debris to lurk, awaiting passing prey. Their diet includes the freshwater crayfish (Paranephrops spp.), aquatic and terrestrial insects, and spiders.[3]

Status

The IUCN has rated the giant kokopu as "Vulnerable". Its status was last assessed in 1996 and the IUCN is intending to re-evaluate it soon.[1]

References

  1. ↑ 1.0 1.1 McDowall, R.M. & Simons, M. (1996). "Galaxias argenteus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 2013-12-29.
  2. ↑ David et al 2002
  3. ↑ 3.0 3.1 "Giant kokopu". NZ Freshwater Fish Database. Retrieved 2013-12-29.