Effects of temperature and salinity on growth, hatching rate and survival of the giant freshwater prawn, Macrobrachium rosenbergii (de man) under captive conditions

Abstract

The present study was conducted to know the effect of different levels of temperature (26 oC, 30oC and 34 oC) and salinity (0, 6, 8, 12, 16 ppt) on growth, hatching rate and survival of female Macrobrachium rosenbergii under captive conditions. Juvenile prawns of 0.32± 0.031g and 2.9±0.508 cm were reared for 12 months. The results exposed that growth of the prawn was increased as temperature increased from 26to 30oC then the growth declined at the highest temperature (34 oC). Also as salinity increased from 0 to 16 ppt, growth of females decreased at all temperatures tested. The highest total length (15.6cm) and total weight (42.1g) were obtained at a 30oC temperature and 6 ppt salinity. Under the above conditions, the weight of eggs increased significantly up to 4.56g, while the lowest weight (0.10g) was obtained at 34 oC-0 ppt. The incubation period was significantly affected by temperature. The longest mean period (26 days) was recorded at the lowest tested temperature (26 oC) with all salinities, while the shortest one (18 days) was reported at 30oC at 6 ppt and at 34 oC at 6 ppt. The hatching rate was increased (ranging from 27 to 75 %) as salinity increased at all treatments. The highest hatching rate (75%) was observed at (30 oC – 6 ppt), while the lowest rate was found at 0 ppt with all temperatures tested. The number of accumulative berried females maximum (Jan to March) during winter to early summer session and it was decreased as salinity increased from freshwater to 16 ppt. While the highest number was observed at 30 oC temperature and 0 ppt salinity and the lowest number was one 34 oC-16 ppt. It was clearly found that optimum level of both temperature and salinity for growth, reproduction and hatching success of M. rosenbergii was 30oC temperature and 6 ppt salinity.