Farming freshwater prawns

TABLE 3Artificial brackishwater (12 ppt) forM. rosenbergii hatcheriesSALT QUANTITY (G/M 3 )Sodium chloride (NaCl) 9 200Magnesium sulphate (MgSO 4 .7H 2 O) 2 300Magnesium chloride (MgCl 2 .6H 2 O) 1 800Calcium chloride (CaCl 2 .H 2 O) 467Potassium chloride (KCl) 200Sodium bicarbonate (NaHCO 3 ) 67Potassium bromide (KBr) 9NOTE: WEIGH AND DILUTE THE SALTS INDIVIDUALLY WITH PREVIOUSLY FILTERED FRESHWATER. ADD THE RESULTING SOLUTIONS TO A TANK IN THE ORDERSHOWN ABOVE, AND MIX THOROUGHLY USING A PVC STIRRER. THEN ADD FRESHWATER UNTIL THE SALINITY IS REDUCED TO 12 PPT. MAINTAIN THE FINAL SOLU-TION UNDER STRONG AERATION FOR 24 HOURS AND ADJUST THE SALINITY AGAIN TO 12 PPT, IF NECESSARY, BEFORE TRANSFER TO THE RECIRCULATION SYSTEM.SOURCE: VALENTI AND DANIELS (2000)OTHER REQUIREMENTS FOR HATCHERY SITESIn addition to having sufficient supplies of good quality water, a good hatchery site shouldalso:have a secure power supply which is not subject to lengthy power failures. An on-siteemergency generator is essential for any hatchery - this should be sized so that it hasthe output necessary to ensure that the most critical components of the hatchery (e.g.aeration, water flow), can continue to function;have good all-weather road access for incoming materials and outgoing PL;be on a plot of land with an area appropriate to the scale of the hatchery, that hasaccess to the quantity of seawater and freshwater supplies required without excessivepumping. The cost of pumping water to a site elevated high above sea level, for example,may be an important factor in the economics of the project;not be close to cities, harbours, mines and industrial centres, or to other activitiesthat may pollute the water supply;be situated in a climate which will maintain water in the optimum range of 28-31°C,without costly environmental manipulation;have access to food supplies for larvae;employ a high level of technical and managerial skills;have access to professional biological assistance from government or other sources;have its own indoor/outdoor nursery facilities, or be close to other nursery facilities;andbe as close as possible to the market for its PL. In the extreme case, it should not morethan 16 hours total transport time from the furthest farm it will be supplying.2.2 Outdoor nurseries and grow-out facilitiesThe success of any nursery facility or grow-out farm depends on its access to good marketsfor its output. Its products may be sold to other farms (in the case of nurseries), directly tothe public, to local markets and catering facilities, or to processors or exporters. The needsand potential of each type of market need to be considered. For example, more income mayresult if you can sell your market-sized prawns alive. The scale, nature and locality of theFRESHWATER PRAWNS16