Live transportation of Macrobrachium rosenbergii (De Man) in chilled sawdust

Abstract

Three cooling rates of 1.26±0.09°C h−1 within 8 h (slow, T1), 2.52±0.18°C h−1 within 4 h (moderate, T2) and 5.04±0.36°C h−1 within 2 h (fast, T3) were tested to cold-anaesthetize farm raised Macrobrachium rosenbergii (De Man) (45–52 g) in each case from 25°C down to 15±1°C in a refrigerated chilling tank, provided with aeration. The cold-anaesthetized prawns subjected to each chilling rate were packed in an insulated cardboard box (triplicate) between two layers of moist and chilled (2–3°C) sawdust, and kept inside a chilled storage cabinet at 15±1°C, for set durations of 6, 9, 12, 15 and 18 h. Survival was determined by revitalizing the prawns in aerated water with an initial temperature of 20°C, which was raised to 29±1°C within 3 h. The experiment was repeated using berried females acclimated to brackishwater of 12 g L−1 salinity and the percentage survival recorded after live storage for durations ranging from 6 to 24 h at intervals of 3 h. Statistically valid safe durations for obtaining 100% survival of the cold anaesthetized and live stored prawns were determined using probit analysis at the three chilling rates tested, and were found to be 7.39, 6.98 and 4.54 h in the case of adult prawns, and 7.87, 8.17 and 6.43 h for berried females for T1, T2 and T3 respectively. For practical purposes, the durations that yielded 95% survival rates were computed to be 16.47, 12.14 and 8.35 h in the case of adult prawns and 18.49, 19.02 and 11.11 h for berried females for T1, T2, and T3 respectively. The berried prawns revitalized after live storage were incubated in tanks and the zoea larvae reared up to postlarvae (PL-5), and compared against a control. No significant difference was found in larval hatch fecundity, survival rate and the production of PL L−1 between the treatment and control, indicating that the method of cold anaesthetization and live storage of berried prawns could be used for successful transportation of broodstock.