Effects of salinity on survival, growth, haemolymph osmolality, gill Na + ‐K + ‐ATPase activity, respiration and excretion of the sword prawn Parapenaeopsis hardwickii

The present study aims to evaluate the effects of salinity (8‰, 12‰, 16‰, 20‰, 24‰, 28‰, 32‰ and 36‰) on survival, growth, haemolymph osmolality, gill Na+-K+-ATPase activity, respiration and excretion of the sword prawn Parapenaeopsis hardwickii. Only one shrimp at 8‰ lived, while there was no significant difference in survival rates from salinity 16‰ to 36‰. Growth performances were improved at salinity from 16‰ to 28‰, and the greatest growth performance was predicted to occur at 22.1‰ using the quadratic equation. The haemolymph osmolality of the sword prawn significantly increased with an increase in salinity (from 12 to 36.4‰). The isosmotic point was equivalent to 0.8067OsM kg−1, which corresponds to salinity 27.0‰. The gill Na+-K+-ATPase activities at 12‰ and 16‰ were significantly higher (p < 0.05) than those at 28‰ and 32‰; the lowest gill Na+-K+-ATPase activity was predicted to occur at 27.7‰. The oxygen consumption rate at 16‰ was significantly lower than that at 28‰, the highest oxygen consumption rate was obtained at 28‰, and it slightly decreased at either side of the 28‰ salinity. The ammonia excretion rates at 12‰ and 16‰ were significantly higher than those at salinities from 24‰ to 32‰; it linearly decreased with an increase in salinity from 12 to 36‰. The O/N ratio linearly increased with an increase in salinity from 12 to 36‰. Therefore, the sword prawn subadults can tolerate a range of salinity (12–36‰), and the optimal salinity range was from 20‰ to 28‰. Therefore, the sword prawn can feasibly be cultured in the majority of coastal areas.