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Advances in KOURA FARMING BY PIETER WILHELMUS I n the early 1960s, the then Department of Fisheries did some trials on koura farming. As a result, they determined koura would not be viable, as they would take three years to reach a weight of 35g. Current trials have produced far different results from those early days, with fi sh averaging 55g in two years and broodstock males in excess of 200g. I started farming in 1993, just after moving to Marlborough with a number of years of freshwater salmon farming under my belt and keen to have my own freshwater fi sh farm. We found a suitable site up the Wairau Valley and began the paperwork war to establish a salmon farm. I didn't want to have all my eggs in one basket, so, enter the koura. I had caught these as a child, having fun and a good feed at the same time. So I decided to set up an aquarium trial in our shed in the middle of town to see how they would breed. The tank was about half a cubic metre in size and had an artifi cial cover, plus natural weed for food and cover. I collected three males and three females, put them in the tank and left them to it. I fed them worms and salmon food, and the natural weed was also available for them to eat. Twelve months later I had so many hatchlings it wasn't funny, so I had to end the experiment. By March 1995 we had a small salmon farm Juveniles built and fi sh in the water. At that time David Smythe, who had done our consent work for the farm, said if I wanted a partner to help get the koura farm going to give him a ring. So it was that New Zealand Clearwater Crayfi sh (Koura) Ltd was set up to help grow and market the Paranephrops planifrons that Ormond Aquaculture Ltd had started. The fi rst trials were very basic, using some large plastic tanks, just to establish growth rates and survival in the fi rst 12 months. These were only partially successful, as the growth rates were good but the survival rates were affected by cannibalism. We determined that koura needed lots of room and a lot of cover. Two races were dug out in the natural gravel and compacted to stop most of the water loss to ground. Water was supplied by gravity, just like a fl ow-through salmon farm. The races were left for 12 months to become just like a natural stream, with lots of weed and grass cover, before being stocked. Over the next few years we had to fi nd the best way to grow koura. We started by leaving things natural and relied on natural recruitment and harvesting what was ready each year. The system worked okay, but we weren't getting enough fi sh of market size coming through, and it was taking a lot of time to select these fi sh from the others. The system had to change, so we decided to have separate classes for each year. For this to happen we had to have a separate pond for broodstock. Over the next six years we did three different trials, ranging from using a hatchery to get juveniles to stock races with females in protected baskets to hatching out young directly into predator-free races. This gave us the chance to selectively breed for growth and colour. We have now settled on a system of hatching out fi sh into dedicated rearing races until they are 12 months old. These are graded out to grow on for another two years or more in larger races. Our outdoor hatchery is still used to hatch out selectively bred crosses, and the tanks also double for mating selective crosses for colour and growth. Koura moult and grow fastest in their fi rst year, and this gave us somewhere to start improving growth. Koura start breeding in mid-March and hatchlings start Red koura appearing in mid-November onwards, depending on how cold the winter is. If we could get the hatchlings out in early September we could get three or four months of extra growth in the fi rst year. A trial was started in an aquarium to artifi cially incubate koura eggs. It was a pretty simple set-up. A tank was insulated and heated to a selected temperature. The koura eggs were acclimatised slowly to the higher temperature and kept in the dark, with regular water tests 6 ■ NZ AQUACULTURE ■ NOVEMBER/DECEMBER 2011