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ACROSS THE DITCH Freshwater aquaculture – UNTAPPED potential BY JOHN MOSIG G 'day Kiwi, how's it going over on your side of the Ditch? After 14 years of below average rainfall, the East Coast over here has had some serious catch-up rainfall. It knocked us around a bit when it happened, but gee, it's great to see the country in full cry again. I read Vince Scully's piece on koura and mullet (in Aquaculture issue 39) and I agree with him on both scores. Firstly, freshwater crayfi sh have a so far untapped potential to be a serious aquaculture product and secondly, polyculture with mullet has equal potential. Let's examine the situation. The two bookends – a reliable supply of quality seedstock and a healthy market – must be in place for an aquaculture venture to be successful. The cost of production must be such that it doesn't push the product up into the rarefi ed price bracket of the white tablecloth market. In other words, the fi sh must be cheap to feed and take as short a time as possible to reach market size. Finally, and this is a must for investors, there must be enough potential technical up-side to add value to the balance sheet as well as the profi t and loss account. I can speak with some authority on freshwater crayfi sh, so we'll start with them. Pardon me if I concentrate on Aussie crayfi sh – yabbies in particular – but you'll be able to compare the comments with the trans-Tasman situation. There'll probably be some species-specifi c behavioural differences, but it's my guess they'll have more in common than otherwise. When it comes to markets, yabbies, redclaw (C. quadricarinatus) and marron (C. cainii and C. tenuimanis) have an established mystique. The depth of that mystique has led many potential crayfi sh growers to base their marketing strategy, and consequently their downfall, on the assumption the world can't get enough of their product. There is a market for freshwater crayfi sh, but when you talk to the hardheaded providores at the wholesale fi sh market, the glassy-eyed mystique that has blurred your marketing vision gets a quick polish. These lads know the depth of the market and pay accordingly. So the question to be asked is, can the cost of production be reduced so the product can be presented inside the budget of the wider seafood-consuming community? (Look no further than mussels for proof of that, eh?) The answer is simply yes, the cost of production can be reduced to levels that make the animal an attractive addition to the menu for those on a lower to middle-range budget. As with all wild creatures, selection for a genotype that displays a predilection for farming can only be a plus. Although the animal tends to be labour-intensive, it can be fed relatively cheaply by generating a natural food web in the ponds. When 12 ■ NZ AQUACULTURE ■ NOVEMBER/DECEMBER 2011 coupled with farming friendly, faster-growing seedstock, this translates to higher yields over a shorter time, which in turn translates into lower production costs. To cover the other bookend, seedstock supply, producing freshwater crayfi sh under controlled conditions in a hatchery tends to be labour-intensive, but the rewards pay for the outlay and effort. Under controlled conditions, the seedstock cannot only be genetically improved, but also it can be produced to match the most advantageous time to stock the ponds. In the wild, the female takes advantage of the warming spring to put condition into her eggs. In a hatchery, broodstock conditioning can be done in advance of the improving season so the newly hatched juveniles can be stocked as soon as conditions pick up. As for genetic improvement by selection, for an animal that reaches reproductive maturity in three to six months, the potential for improvement in growth, conformation, food conversion and all-round vigour is appealing. So what have we got? An animal with market appeal and acceptance, room for signifi cant productivity improvements and its feed source is independent of the fi sh meal supply vortex faced by say, salmon producers. Where do I sign up, I can hear you asking? Now let's look at mullet. I'm one of those people who think all fresh fi sh tastes good, and I have a particular liking for fresh mullet. There was a seafood café known as Jake's on the coast of New South Wales at Karuah. It was on an estuary and you could bet your bottom dollar the mullet at Jake's was fresh. The only time I ever drove straight through 60g table yabbies Karuah was when Jake was on holiday or the sandwich board didn't feature mullet. Jake's was fresh because it was caught in the estuary or up one of its many tidal branches. So, if it was farmed you could make sure it reached the market fresh. Then there's the added value option Vince suggested of smoking them. I've never tried smoked mullet but after sampling some of the marinades at Jan Dissel's Anatoki Salmon on Golden Bay, I can image it is mouthwatering. Hatchery-reared seedstock can be produced and they are akin to vacuum cleaners in the ponds. They can be fed a natural diet the same as freshwater crayfi sh, or at least a low-value manufactured diet. Crayfi sh can also be fed a supplementary diet if the economics of the day dictate, and the crayfi sh have a high turnover production cycle. Market-sized animals of 60-80g can be produced in a summer. This is looking better every time I read through it. Before you rush into it, get in touch with Vince and he'll explain why it ain't all beer and skittles.