Aeration level in HDPE-lined nursery ponds that optimizes yield and production cost of preadult redclaw crayfish, Cherax quadricarinatus

The potential for commercial Australian redclaw crayfish culture is considered very significant. However, information on the effect that different water exchange and aeration levels has on growth, survival, yield and nursery production costs of redclaw is limited. We evaluated the effect of aeration levels in the yield and production cost of preadult redclaw crayfish, Cherax quadricarinatus, during the nursery phase. In a preliminary trial, 4 levels of water exchange: 0%, 2.5%, 5% and 7.5% day⁻¹, were tested in 1.7 m diameter (2.26 m²) tanks, stocking 3.0 ± 0.2 g juveniles at a density of 15 juveniles m⁻². After 60 days, the physicochemical water quality parameters were within the recommended intervals for cultivation of the species. Final weight, survival, biomass and FCR's of pre-adult C. quadricarinatus did not show any significant differences (p > 0.05) among treatments so we conclude that adequate production of C. quadricarinatus during zero-water exchange nursing is feasible. With the previous information, 4 aeration levels (0, 6, 12 and 24 hr day⁻¹) were evaluated in triplicate 100 m² HDPE-lined outdoor ponds. Juveniles (3.5 ± 0.5 g) were stocked at a density of 15 juveniles’ m⁻². After 84 days of cultivation, survival was not significantly different among treatments and varied within 86–87%. The highest final average weight, growth rate and biomass were obtained with 12 h of aeration per day (3.2 ton ha⁻¹), but there were no significant differences from those obtained in ponds with continuous aeration (24 hr day⁻¹). The feed conversion rates were within 0.72 − 0.75. We conclude that it is possible to maximize C. quadricarinatus production in HDPE-lined ponds without water exchange, maintaining aeration at a rate of at least 12 hr day⁻¹. A cost analysis shows that, with this strategy, it is possible to reduce the electricity costs required for water pumping and aeration in 70% and 50%, respectively. With this, a reduction of 11.17% in the production cost of pre-adult C. quadricarinatus during the nursery phase is achieved, compared with the best published reports.