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ACROSS THE DITCH CLIMATE change and recirculation technology BY JOHN MOSIG ow's it going over there in Kiwi? Cold? Along the eastern states we've just had our hottest July on record. If you can call July hot. Now, you'd expect that to suggest something to our political leaders – and to the naysayers and climate change deniers? The greatest moral challenge of our time? Not if it's not a vote catcher. And with jobs disappearing right left and centre, climate change is not really a vote catcher. What's this got to do with aquaculture? Well, fish being cold blooded have a narrow band of temperature within which they operate efficiently. If the climate conditions are going to be all over the shop, it's going to see the fish not only confused, but with a good chance of being outside their optimum efficiency band. Even getting close to their upper and lower critical limits. And we all know the havoc elevated stress levels can wreck on a fish farm. Take the example of the Atlantic salmon sector down in Tassy. It's a great place to grow salmon. Compared to Norway and Chile, the winter water temperatures are positively summery. For a salmon that is. Until the dreaded El Niño drifts across to our side of the Pacific basin. When the Southern Oscillation Index favours the conditions that bring drought to the east coast of Australia, water temperatures track land temperatures and the water around the salmon cages becomes a positively hostile environment. Feeding rates have to be reduced, or feeding even held off, and the stressed fish are prone to suffer from whatever it is that's going around at the time. We won't go into it, but let those amongst us who haven't buried fish shout the first 10 rounds on Friday, for theirs is truly a charmed life. The outcome of this is reflected in several ways. The obvious one is loss of production. But the other losses are more insidious. Not only are the fish stressed, husbandry loads are also increased. Risk management becomes more intense, the removal and disposal of the mortalities adds to the cost of the survivors, and the emotional strain on the operators. On top of that, under Murphy's Law, it's always the fish in the production cycle closest to market weight that find themselves under the most stress. We're talking serious numbers and serious values. These are the obvious ones. How about when the fish hit the processing floor? It costs just as much to fillet a 3kg fish as it does a 2.5kg fish, only you're getting nearly 17 percent less product. So where are we going with this? The age of the climate controlled aquaculture would appear to be upon us. Sure it comes with a cost, but if we use the pig and the poultry industries as a road map, atmosphere controlled production environments, particularly when the animals are in the high metabolic juvenile phase, has delivered dramatic increases in productivity. So that would have to suggest something, wouldn't it? That the perceived capital and operating cost of indoor fish farming when measured against the productivity gains has advantages unattainable to farmers operating in an environment at the mercy of the elements. Not to mention the removal of seasonality as a limiting factor. But there're steak knives with indoor farming. You see, H there are two basic environmental factors involved - water temperature and water quality. By moving indoors, growers give themselves absolute control over both.True, water quality management is not a box of birds, but the science is long established and the technical elements of the engineering have moved ahead dramatically over the last decade or so. The steak knives? Well, once those factors are under control, any improvement in feed efficiency and/or the increase in genetic potential provided by the genotype of the species being grown is magnified by the overall percentage increase in the time the fish are at their optimum growing conditions. Let's say, in broad terms, that the summers are a bit on the warm side and through a range of factors 50 percent of production potential is lost. In the depths of winter the water temps are below optimum and 25 percent of growth is lost. Under that temperature regime we have lost say, six weeks of production in the summer and another three weeks in the winter.That's 17 percent of productivity that's been lost. Nine weeks during which time the farm still had to cover its fixed costs but from which it gained no income. That 17 percent is then magnified by the benefits of genetic and nutritional technology that has been gained. Keeping in mind that any technology will have a price whether you pay for it yourself through R&D or buy it in from a hatchery or feed manufacturer.You'll have to measure the gains against the costs. I can hear growers saying it on both sides of The Ditch - 50 percent productivity loss is a bit steep. Okay; never mind the FCRs, let's just say a system is able to accept a feeding rate of 1.5 percent of the weight of the fish in the cages/ponds, and that has to be cut back to 0.5 percent. For argument's sake let's say 0.5 percent is a maintenance diet. The fish are fine, but productivity is zero. If water conditions are such that you can't feed at all, the fish draw on their energy reserves. That's minus productivity and represents loss of growth that has to be made up. In simplistic terms, every day of energy reserves lost, means a day of feeding to get back where you were. So, that's actually two days of zero growth. Remember, these are just broadly speaking examples, but it helps present the picture, and the opportunity for that matter. It's not the end of fish farming as we know it. But where the climate makes recirculation farming economically feasible, at least we know that there's an option. SEPTEMBER/OCTOBER 2013 ■ NZ AQUACULTURE ■ 13