Intensification of redclaw crayfish Cherax quadricarinatus culture I. Hatchery and nursery system

Intensification of an indoor hatchery and nursery system for the Australian redclaw crayfish Cherax quadricarinatus (von Martens) (Decapoda: Parastacidae) was obtained by increasing the surface area available for the crayfish juveniles and by synchronizing the age of the hatchlings held in each tank. The former improvement was facilitated by distributing an artificial seaweed-like material throughout almost the entire volume of small (275 1) hatching tanks. As the number of egg-bearing females was increased from 3 to 8 per hatching tank, the number of juveniles per liter also increased to as many as 6.5 juveniles/1, without reaching an apparent upper limit. The hatchlings were kept in the tanks for 75 days from the day females were found to be gravid and then harvested and graded according to size. The average juvenile weight at harvest was 0.34±0.04 g. The weight distribution of the juvenile males was not significantly different from that of the juvenile females on the day of harvest, and in both the distribution was positively skewed.