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Whitebait the NEXT BIG THING? W hitebait is a much-praised and highly- prized seasonal delicacy in New Zealand. The bait are the juveniles of a handful of fi sh species belonging to the Family Galaxiidae, though well over 90 percent of the whitebait are believed to belong to just a single species: (Galaxias maculatus). The juveniles, the inanga some 45-50mm in length and around 0.4g in weight, are several months old by the time they endeavour to make their way into freshwater rivers and streams from the sea, and when many meet the nets from eager fi shers, especially along the West Coast of the South Island. The high price of whitebait has prompted at least one entrepreneur in the North Island to develop a ranching approach to growing whitebait. Overseas, whitebait have also been in the spotlight, and this is best illustrated by the recent efforts of a Chilean group to breed inanga for the purpose of growing whitebait as cash crops. However, broodstock that are more fecund (producers of larger numbers of eggs) than inanga were considered a necessity to increase profi tability. It is from this viewpoint that Matthew Wylie, a keen amateur fi sh keeper and Zoology graduate student at the University of Otago, opted to explore the possibilities of using the giant kokopu, or 'GK' (Galaxias argenteus). This fi sh is thought to only make a minor contribution to the whitebait catch, but because of its large size, up to 40 cm, and high fecundity, 10-25,000 eggs, were seen as key attributes that could prove suitable for generating whitebait, whether for aquaculture or conservation purposes. His proposal was funded through through a Te Tipu Putaiao Fellowship awarded by the Foundation of Research, Science and Technology. Starting in late 2009, Matt employed a two-pronged a spent giant kokopu Matt holding approach: he took monthly samples (blood and developing eggs) from both wild fi sh and from fi sh that were captured and maintained indoors under a simulated natural photothermal regime. To by-pass the need for sacrifi ce, developing eggs were sampled by minor surgical manipulations. In doing so, Matt could compare natural egg development and development under captive conditions, leading to fi ndings that were presented to an international scientifi c audience in 2011. He found that fi sh started to yolk their eggs from February for a 3-4 month period, by which time egg growth had completed. Collections of wild fi sh were made until late June, when males were running ripe and females had fully distended abdomens. On return to our holding facilities, these fi sh BY MATTHEW WYLIE MSC AND DR MARK LOKMAN, UNIVERSITY OF OTAGO Newly hatched larvae A one year old giant kokopu were maintained until ovulation was confi rmed a few days later, and GKs were spawned artifi cially without the need for any hormonal intervention. The captive-held fi sh also spawned, reinforcing that wild giant kokopu can be readily acclimated to captive conditions and captive feeds, and that they can eventually reach spawning condition. Spawning of wild fi sh was repeated successfully in 2011 and 2012. Thousands of eggs hatched after 3-5 weeks at 10-17 degrees Celsius. Matt has been rearing the larvae from the 2011 cohort successfully to whitebait on brine shrimp, and they were thereafter weaned onto salmon starter. At a leisurely pace, the fi sh reached 40g within the fi rst year in recirculating tanks. The ease of propagation and the robustness of the larvae when reared in seawater suggest that this species at least, has the biological attributes to be considered as a valuable species for New Zealand's future aquaculture industry. Indeed, GKs may potentially contribute to species diversifi cation, a perceived need by Aquaculture NZ, to help grow the industry. SEPTEMBER/OCTOBER 2012 ■ NZ AQUACULTURE ■ 13