A 15‐day trial was conducted to determine the effect of dietary potassium on the requirement of aqueous potassium in P. vannamei under inland saline water (ISW). Two experimental diets viz. control (C) and control with 1% KCl (K) were fed to P. vannamei as six treatments viz. FW (reared in freshwater and fed on C), ASW (reared in artificial seawater and fed on C), ISW (reared in inland saline water and fed on C), ISW+eK (reared in potassium fortified ISW and fed on C), ISW+fK (reared in ISW and fed on K) and ISW+½eK+fK (reared in 50% K fortified ISW and fed on K). The samples were collected on selected intervals (0th day, 1st day, 7th day and 15th day), and mortality was recorded continuously. Total mortality (100%) was observed in FW and ISW. 100% survival was recorded in ASW and ISW+½eK+fK, while a lower survival was observed in ISW+fk. The haemolymph osmotic and ionic concentrations were lowest in FW and ISW. The principal ions (Na+, K+ and Cl−) and osmolality of ISW+½ eK+fK were restored to the level of ASW within 15 days. Na+K+ATPase activity was increased in ISW while lowered by K supplementation. HSP70 expression was upregulated in ISW fortified with K partially or entirely. However, the groups reared in ISW and ISW supplemented with feed potassium alone could not enhance HSP protection up to the level of ISW+eK and ISW+½ eK+fK groups. Overall, 50% of aqueous potassium can be compensated with 1% dietary KCl, without affecting survival and ionic homeostasis.

Parasitic diseases have been the major source of concern and cause considerable losses in the freshwater aquaculture of India. Fish parasites proliferate quickly in favourable settings, compromising fish health and frequently resulting in high mortality. Identifying and implementing appropriate control techniques is the need of the hour to combat the diseases. Emamectin benzoate (EMB) is an efficient infeed therapy for ectoparasite control in fish. The aim of the present study was to determine the withdrawal period of EMB in silver carp (Hypophthalmichthys molitrix) commercially important fish species in southeast Asia. The depletion of EMB residues in silver carp muscle treated with a dose of 50 μg kg−1 body weight (BW) day−1 for seven consecutive days was assessed. Muscle tissue was sampled on the 7th day of EMB feeding and 1st‐, 3rd‐, 7th‐, 14th‐, 21st‐, 35th‐ and 41st‐day post‐medication (PM) for QTRAP 4000 LC–MS/MS analysis. The data revealed that the level of EMB in the fish muscle was 13.0 ± 0.1 parts per billion (ppb) on the 0th day of withdrawal. The residue levels were reduced significantly on the 3rd day, with traces of EMB recorded by 21st‐day PM and reached undetectable levels by 31st day PM. Considering the maximum residue limit (MRL) of 100 μg kg−1 for fish muscle, the present study's findings support the usage of EMB in silver carp under the conditions employed in the study. The current study provides crucial information on the use of EMB as an antiparasiticide in silver carp, considering the food safety issues.