Giant Kokopu eggs 15 days post spawning
Paul Decker, of MTI, said "These are our grandchildren whose parents were our fi rst born." Although the mechanics of fi sh egg fertilisation are not complicated, creating the right conditions for the synchronised production of good quality, fully mature eggs, and milt or fi sh semen, requires careful culturing and monitoring of the parent fi sh. "Hatching the eggs is a painstaking procedure to ensure that they are not physically damaged, and are protected from diseases and attack by micro predators. Throughout the incubation period it is critical that the eggs are kept in ideal conditions with temperature, moisture and aeration levels that suit them. A major part of the breeding success has been to achieve the hatching and larval raising on such a large scale. We are now in our fourth week of breeding and are hatching literally thousands upon thousands of Giant Kokopu whitebait every 21 days after egg laying. With production at these levels, security of supply for commercial whitebait farming can now be assured. "Within the next 10 weeks the juveniles will have grown to what the public recognise as whitebait and some of our aquaculture students and staff will be taste testing samples of these delicious fi sh." Hatchery-produced fi sh fry for use in aquaculture must be healthy and have high survival rates. Poor incubation and larval raising conditions can produce weak offspring, but according to Decker, "The fry being raised at MTI's hatchery are already showing excellent health, and because of precautions taken, they are disease free." This will be invaluable for stock that is grown on for commercial whitebait production, but also for stock that is to be released into the wild for conservation enhancement projects. In the past, survival of transferred fi sh from other sources has often been below expectations due to health issues.
MTI sees two distinct but complimentary benefi ts to New Zealand from the hatchery breeding of Giant Kokopu: • The fi rst is for conservation, with the goal being to release adult fi sh back into restored natural waterways that have yet to be recolonised.
• The second is their commercialisation, as a farmed whitebait fi sh to meet the demand for dishes such as whitebait fritters. For this, culture could be on a year round basis to make farming of this delicacy commercially viable. MTI's Warkworth facility is a conservation fi sh hatchery
actively involved in a collaboration with the Department of Conservation to reintroduce native fi sh to natural habitats. They are also helping Auckland Zoo with their native fi sh breeding programme, and native fi sh display. The researchers are hopeful that the farming of whitebait
Giant Kokopu embryos
Giant Kokopu emerging from egg
Giant Kokopu newly hatched
will have real conservation benefi ts in that commercial harvesting will reduce pressure on natural populations enabling them to recover, demonstrating that conservation and commercial initiatives can be complimentary.
SEPTEMBER/OCTOBER 2012 ■ NZ AQUACULTURE ■ 15
