Experimental pond production of marron, Cherax tenuimanus (Smith) (Decapoda: Parastacidae)

Forty-two, 4-month pond trials were carried out on a large indigenous crayfish in south-western Australia — a candidate species for commercial aquaculture. Since growth rate and density are inversely related in this species the aim was to establish an intermediate range of density giving commercially acceptable values of growth rate and biomass. Survival over 4 months averaged 80.5% (30.7–100%) and was independent of density in the range 2–15/m²; low values (two below 50%) were due to oxygen depletion from overfeeding. The complex relationship between mean individual weight gain/4-month trial and initial mean individual weight was described indirectly using Mauchline's (1977) linear plot of log growht rate in length against initial length. A multiple regression equation accounted for 93.3% of the variability in log growth rate with 45.7% due to initial size, 40.6% due to seasonal water temperatures, 6.1% due to initial density and 0.8% due to feeding rate. Similar transformations were used to relate statistically production and biomass change to initial mean weight. Growth, production and biomass schedules were constructed for the most favourable temperature area of the south-west. A mean weight of 45 g at a biomass of 2100 kg/ha was predicted for the end of the first year of life and 111 g at 3175 kg/ha for the second year. Wide variability in individual weights represents a marketing problem. Plant material (poultry and lucerne pellets, compost) was supplied at rates of up to 1.0 kg/m² per 4 months as a substrate for detrital formation. Pollution from these materials generated limiting oxygen deficiencies.