The impact of salinity and temperature stress on survival, behaviour, immune response, and proximate composition of giant freshwater prawn Macrobrachium rosenbergii

Salinity and temperature significantly affect the growth and production of giant freshwater prawn Macrobrachium rosenbergii. This research investigated the effect of these two vital parameters on behaviour, survival, haemocyte-based cellular immunity, and proximate composition of M. rosenbergii. Adolescent prawns were exposed at five different salinities (0, 5, 10, 15, 20 ppt) and temperatures (22, 26, 30, 34, 38 degrees C) at a stocking of 6-ind/25-L glass tank with three replication and nursed up to 168 h. Prawn showed normal behaviour and movement up to salinity of 10 ppt, while rising salinity to 20 ppt associated with abnormal behaviour caused 50% mortality within 72 h and showed complete mortality after 96 h. Prawns exposed at 22-30 degrees C exhibited normal behaviours, while uplifting temperature to 34 degrees C showed unusual behaviour and mortality. Further increase of temperature to 38 degrees C, survival rapidly decreased to 33.33% after 24 h, and complete mortality happened within 72 h. Total haemocyte count and differential haemocyte count did not exhibit significant variation at salinity <= 10 ppt and temperature <= 30 degrees C, while there was a significant declination at higher salinities (>= 15 ppt) and temperatures (>= 34 degrees C). Interestingly, after a significant fall in protein content at 30 degrees C, it started to increase at higher temperatures. Meanwhile, a significant decrease in lipid content was recorded at salinity >= 15 ppt. Water quality measurements were within acceptable norms for prawn aquaculture throughout the experiment. According to this study, prawns' growth, behaviour, and immune system were mostly unaffected by saline levels up to 10 ppt and temperatures below 30 degrees C; thus, ranges could be adopted for climatically altered coastal environments.