Culture of the Australian red-claw crayfish (Cherax quadricarinatus) in Israel - IV. Crayfish incorporation into intensive tilapia production units

This study tested the suitability of the Australian red-claw crayfish Chera x quadricarinatus for rearing in an intensive culture system as a supplemen t to Oreochromis niloticus. Fish were grown in twelve 5.5 m(3) tanks at hig h density (33/m(3)) for 133 days, alone or with crayfish at two stocking de nsities (10/m(2) and 20/m(2)) with added shelters or with crayfish at the l ower density (10/m(2)) without shelters. Tilapia survival ranged 90.3-95.0% with no significant differences among treatments. The growth rate of the t ilapia raised with crayfish (2.05 g/day) was significantly higher than that of tilapia grown alone (1.88 g/day) probably because the fish were feeding on part of the crayfish pellets. Among treatments, there were no significa nt differences in fish yield. Crayfish survival was extremely low in the 'n o shelter' treatment (2.9 +/-2.7%) but reasonable (approximately 60%) when raised with shelters. The growth rate of the crayfish raised with shelters was significantly higher at the lower density (0.21 g/day)than at the highe r density (0.18 g/day). Further research is needed on rearing tilapia and c rayfish to market size in intensive systems, to establish the economic prof itability of this culture strategy.