Culture strategies for redclaw, Cherax quadricarinatus (von Martens, 1868) (Decapoda: Parastacidae) and silver perch, Bidyanus bidyanus (Mitchell, 1838) (Perciformes: Teraponidae) : natural foods and artificial shelters

The demand for fish meal in aquaculture is an expensive part of aquaculture operations and this has generated interest in alternate food sources and use of natural live food. Use of traditional live food such as microalgae and zooplankton in aquaculture is reviewed. The current taxonomy of the redclaw Cherax quadricarinatus (von Martens, 1868), silver perch Bidyanus bidyanus (Mitchell, 1838), and the oligochaetes; Aulophorus sp. (Schmarda, 1861), Branchiura sowerbyi (Beddard, 1892), Tubifex tubifex (Muller, 1774) and the terrestial worm Dendrodrilus rubidus (Savigny, 1826) was elucidated. Culture requirements for worm species and the nutritional and culture requirements for the aquaculture target species were determined as follows: The best substrate for mass production of Aulophorus was 100% cowdung, at a water temperature of 15°C. There was a significant correlation between oxygen concentration and reproduction in Aulophorus sp. with production levels of 3194.5 mg of T. tubifex per cm2 reached within 60 days and 4242.5 mg per cm2 of B. sowerbyi. Both were cultured in a mixture of 75% cowdung, 20% fine sand and 5% mud. An alternate substrate/food (ground peanut/shell, wheat pollard, rolled oats and lucerne pellets) was utilised for the mass propagation of T. tubifex and B. sowerbyi. Production of 2352 mg T. tubifex per cm2 and 2339.34 mg per cm2 of B. sowerbyi was obtained after 60 days. The population density was significantly influenced by substrate type, with highest population densities in the cowdung based substrate. Experimental culture of the terrestial worm D. rubidus was also carried out. Percentage increase in number and mean weight increase of the inoculated worms after a month was 532.2% and 0.50 g and an average of 2797 juveniles weighing 839.1 g was collected from each culture container after four weeks. Trials of oligochaete species as food for C. quadricarinatus juveniles, were conducted, single species and combinations of worm species being used. The nutritive values of T. tubifex and B. sowerbyi, for redclaw stocks from the Gregory, Mitchell, Gilbert, Flinders and Leichhardt river systems of North Queensland were compared with a commercial pellet (Aquafeed) as a reference diet and a lucerne pellet. The nutritive values of Aulophorus sp. and Dendrodrilus rubidus were compared with Aquafeed. Digestibility experiments were performed using Aulophorus sp. and B. sowerbyi.