The growth and survival of western king prawns, Penaeus latisulcatus Kishinouye, in potassium-fortified inland saline water

Western king prawns, Penaeus latisulcatus are a candidate species for culture in inland saline water. Western king prawn survival, growth, condition, osmo- and iono-regulation was studied when reared in potassium-fortified inland saline water for 202 days. PL40 prawns were stocked into three media in 250 L tanks: inland saline water with potassium fortified to 80% (IS80) of the marine water concentration, 100% (IS100) of the marine water concentration and marine water (MW). By the conclusion of the trial, survival was 53% in IS80, 64% in IS100 and 68% in MW. Mean prawn weight, total length, carapace length, condition factor and moult interval were significantly higher (P < 0.05) in MW than in IS100 and IS80. Specific growth rate of prawns in MW was significantly higher (P < 0.05) than in IS80. There were no significant differences (P > 0.05) in osmoregulatory capacity of prawns between various media. Serum Na+, K+, Ca2+and S concentrations were influenced by their concentration in the medium. Ca2+ was the only major cation hyper-regulated and tended to be accumulated, while Mg2+ was maintained at a much lower concentration in the serum than in the medium. Moisture contents in hepatopancreas, tail muscle and exoskeleton and organosomatic indices improved from IS80 to IS100 to MW. The lower growth rates and condition factors of prawns reared in potassium-fortified inland saline water suggests the presence of limiting factors other than potassium concentration. Western king prawns are stronger regulators of divalent cations than monovalent cations and the extra energy required to regulate ions in inland saline water may have been the major cause of lower growth rates.