Professional Skipper Magazine from VIP Publications

Part of the hatchery at Granite Belt Fish Hatchery NATIVE FISH: Granite Belt Fish Hatchery BY JOHN MOSIG T he Donges family have been breeding warmwater Australian native fi sh at the Granite Belt Fish Hatchery since 1987. Situated just out of Stanthorpe on the NSW Queensland border, the farm has a reputation for producing quality fi ngerlings for both recreational and re-stocking markets. They breed Murray cod (Maccullochella peelii peelii), golden perch (Macquaria ambigua) and silver perch (Bidyanus biyanus). Three hundred megalitres of water can be pumped up from the Severn River over a three-year period. The average rainfall is 750mm and falls throughout the year, but being in the sub-tropics, the heaviest falls are in the warmer months. They also harvest runoff water and the three storage reservoirs hold another 300ML. The summer climate is mild, and pond temperatures, even in the shallow plankton production ponds, rarely get above 27 degrees celsius. Nick said they don't have to do much testing. With a pH of over eight, the water is well buffered. He checks the dissolved oxygen and phosphate levels to make sure there is enough to drive the plankton bloom. Over the years he's found that these are the key indicators that need to be monitored when raising fi ngerlings. During winter Nick keeps water in his growout ponds, partly to kill the grass and as water storage itself. When spring approaches, this water is moved to one of the three main storage reservoirs and the ponds are allowed to dry out to prepare them for the cod and perch larvae. Drying them out breaks the build up of any aquatic invertebrates that would prey on the larvae. It also allows the pond to be fertilised and fl ooded to trigger a healthy plankton bloom. The hatchery has been designed and built by the Donges family. Innovation can be seen at every turn: the tractor driven aerators for instance and the ingenious air pump for the hatchery. The air pump consists of a series of diaphragms, cams and mechanical arms, it is belt driven off the mains power. Nick said it was 20 years old and had never let them down. The tanks, bio-fi lters, plumbing and the drum fi lter, were all designed and cobbled together on the farm from stainless steel. 8 ■ NZ AQUACULTURE ■ SEPTEMBER/OCTOBER 2012 The hatchery consists of 16 x 1600L tanks connected to a recirculating system. Each tank has two 200L bio-fi lters using Aquasonic bio-balls, and the water from two tanks goes into a 400L swirl fi lter before going through a 100µm drum fi lter. It is then returned to the tanks via four 120w UV sterilisers. There is an in-line heating tank for each system. The water for the cod is kept at 24 degrees celsius. Nick spreads the season. The cod are bred from eggs harvested from 22 spawning drums. The number of fertilised eggs they get from the drums varies with the season. "A couple of years ago we weaned about 200,000. This can cause more troubles than it's worth. Now we normally do around 100,000," Nick said. They put the cod drums in and start checking the water when the temperature approaches 19 degrees celsius. The … THEY WERE THE BEST COD HE'D EVER TAKEN DELIVERY OF spawning trigger for cod is 20 degrees celsius and the ponds hit that in late September to early October. The cod eggs hatch within fi ve to seven days of collection. The larvae are quite large when they hatch: 10mm to 12mm, and live on their yolk sack for up to 13 days. By this time they have spread out and they are looking for food. Once the hatch has been successful, plankton ponds are fertilised and fl ooded. The juvenile cod have a large gape, and like their parents, will tackle anything they feel they can swallow. Nick makes sure the plankton bloom has matured and that the zooplankton are advanced. He stocks at fi fty larvae per square metre. Under optimum conditions the cod fi ngerlings have

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