EFFECT OF WATER QUALITY PARAMETERS ON GROWTH AND SURVIVAL OF GIANT FRESHWATER PRAWN MACROBRACHIUM ROSENBERGII LARVAE IN PONDS

Abstract

The giant freshwater prawn Macrobrachium rosenbergii (De Man, 1879) is one of the most economically important species with good export market due to attractive size, better meat quality, omnivorous feeding habit and easy breeding in saline pond. The study was conducted to understand the effect of water quality on growth of M. rosenbergii larvae hatched from the beried female stocked at different stocking densities using three saline (approx.12 ppt) ponds having 0.1 ha area each. Three different stocking densities of berried prawns were maintained as T1 (5 kg), T2 (10 kg), and T3 (15 kg). Medium-sized berried prawns (45-55 g, TL 17.8-19.2 cm and 25-40 g, TL14.0-15.2 cm) were initially stocked. Hatching occurred after 2-3 days of stocking of berried females in treatment ponds. But in case of control ponds hatching occurred after 5-7 days of stocking. The larvae were fed with Artemia flakes and egg custard. Water quality was maintained by exchanging 20-30% of pond water once a week. Dissolved Oxygen (mg/l), pH, and salinity (ppt) were monitored. Physico-chemical parameters of soil sample were analysed in two phases - pre-stocking and post-harvesting periods. Mean soil pH (6.71±0.11, 6.41±0.12), mean organic carbon (0.29±0.1, 1.87±0.1), mean available nitrogen mg/100 g soil (24.93±0.21, 30.20±1.1), and mean available phosphorous mg/100 g soil (3.02±0.1, 7.08±0.33) in treatment and control ponds, respectively were recorded during both pre-stocking and post-harvest periods. The first PL stage (7.69 mm) was achieved in 25 days (T1) and in other treatments the size was achieved at 25-29 days. Post larval production (nos.×105/0.1 ha) was recorded (6.0±0.1) in T1, (4.0±0.1) in T2 and (3.2±0.02) in T3 and 2.4±0.21in C1, 1.3±0.14 in C2 and, 0.9±0.14 in C3. The survival rate of post-larvae was found at 27.21% (T1), 9.1% (T2) and, 4.96% (T3) and 13.93% C1 , 4.02% C2 and, 1.81% in C3. Feeding, survival and growth of larvae were adversely affected by mild-acidic pH exposure as compared to neutral pH. Larvae exposed to mild-acidic water pH experienced a prolonged larval period and only metamorphosed to the post-larval stage at day-34. Neutral pH, larvae that metamorphosed to first post-larval was observed on day-25. The negative impact on the feeding, survival, growth and development of M. rosenbergii larvae culture in mild-acidic pH exposure was recorded underlining the significant role of water pH on the growth and survival of M. rosenbergii larvae.