Adult Giant Kokopu
Extinction threat EXTINGUISHED
BY DR JOHN WALSBY
PHOTOS MAHURANGI TECHNICAL INSTITUTE
M
ahurangi Technical Institute based in Warkworth has successfully bred huge numbers of one of New Zealand's rarest native whitebait species, the Giant
Kokopu or Galaxias argenteus, from captive fi sh bred in its conservation hatchery. Work in eel breeding, and over 20 years of breeding the
many millions of grass and silver carp that are used throughout New Zealand for clearing nuisance pond weeds and algae from lakes, have earned MTI an international recognition for its breakthrough successes as a fi sh conservation hatchery. During the last ten years MTI aquaculture scientists and students have been investigating the breeding of many of New Zealand's native fi sh, including the six species that make up the New Zealand whitebait catch. It is widely accepted that the presence of Giant Kokopu whitebait in the South Island West Coast catches provide their renowned, superior fl avour. But in conservation circles there is alarm that this important native fi sh is in serious decline. The Red List of the International Union for the Conservation of Nature's ranks Giant Kokopu as Vulnerable which means they are "facing a high risk of extinction in the wild". From tiny beginnings, Giant Kokopu grow into New
14 ■ NZ AQUACULTURE ■ SEPTEMBER/OCTOBER 2012
Zealand's most impressive native freshwater fi sh. Sometimes dubbed the "New Zealand native trout", adults can grow to two kilograms and exceed half a metre in length. With fi ne dappled markings of rings and crescents over a dark background, and a delicate scatter of gold spots, the Giant Kokopu, is a handsome specimen that is seldom seen because of its rarity. MTI's breeding success is especially remarkable because
the parents were themselves hatched at MTI's laboratory from a small cluster of eggs collected in the wild four years ago. Hatching the eggs, raising the larvae and growing the juveniles through to sexually mature adults from which offspring have been produced, is a major achievement. It is the fi rst demonstration of what fi sh scientists term, "closing the life cycle", or producing a second generation from fi sh hatched and raised in a hatchery. The precise details of natural breeding by Giant Kokopu in the wild have not been reported by fi sh scientists and have been the subject of much speculation for many decades. In the absence of clues from the wild, the current achievement of both spawning and hatching many thousands of this rare New Zealand native freshwater fi sh in its hatchery, is considerable.
