Combined effects of shelter and density on the growth and survival of juveniles of the Australian freshwater crayfish, Cherax destructor Clark, part 2

Two experiments were conducted on newly independent (stage 3) yabbies (Cherax destructor) to investigate the effect of shelter and density on growth and survival under laboratory conditions. The first trial was conducted over 41 days using three density levels, four, eight and 16 per 2.5 l aquarium, equivalent to 150, 300 and 600 m -2 , with and without onion bag shelter. The addition of shelter to aquaria did not significantly enhance growth, survival or yield. In contrast, increasing density reduced the average weight of yabbies and increased yield, but did not affect survival. No interaction was found between density and shelter with respect to either growth or survival. The second trial, conducted over 45 days, examined the effect of three shelter types (onion bags, rocks and small sections of rubber pipe) at a density of 18 per 2.5 l aquarium, equivalent to 650 m -2 . No differences were found in growth, survival or yield between shelter types or between shelter types and a control (no shelter). The results suggest that under most circumstances the use of shelter is unnecessary for the intensive indoor rearing of juvenile yabbies.