Fortification of an Aquafeed with Potassium Chloride Does Not Improve Survival of Juvenile Australian Snapper Pagrus auratus Reared in Potassium Deficient Saline Groundwater

Abstract

This study was done to determine if fortification of a commercial aquafeed with KCl could improve the survival of juvenile Australian snapper Pagrus auratus reared in K + deficient saline groundwater (KDSGW; <5 mg K + L −1 ). Experiment 1 (Exp. 1) tested whether feeding an aquafeed fortified with zero, 25, or 50 g KCl kg −1 for 6 days affected feed intake and survival of fish transferred immediately from estuarine water to KDSGW of the equivalent salinity (20 g·L −1 ). Experiment 2 (Exp. 2) investigated whether an aquafeed fortified with zero, 10, or 25 g KCl kg −1 affected survival, feed intake, and growth rate (SGR) of snapper reared in KDSGW fortified to have 40% or 100% the [K + ] of equivalent salinity estuarine water (20 g·L −1 ). The results of Exp. 1 demonstrated there was no benefit of fortifying aquafeed with KCl; fish transferred into KDSGW stopped feeding and developed symptoms akin to tetany. Some individuals also died and others became moribund. Exp. 1 was terminated according to animal care and ethics guidelines. The results of Exp. 2 indicated the amount of KCl added to the aquafeed did not affect survival, feed intake, or food conversion ratio (FCR) of snapper, irrespective of water treatment. However, SGR and FCR was better when fish were reared in normal estuarine water and KDSGW fortified to have 100% the [K + ] of equivalent salinity estuarine water. Our results demonstrated that juvenile snapper were unable to utilize the KCl added to the aquafeed and were probably reliant on sequestering K + ions from the water column in order to maintain functions involving hydromineral homeostasis. Fortification of aquafeeds with KCl does not ameliorate the negative effects of KDSWG on the survival of juvenile snapper.

Taurine and/or inorganic potassium as dietary osmolyte counter the stress and enhance the growth of GIFT reared in ion imbalanced low saline water

“…The high cost of ameliorating inland saline water (ISA) bodies with potassium salts abates aquaculture potential. Thus, enriching K + through aquafeeds has gained much interest as an alternative ( Booth and Fielder, 2016 , Zaffar et al, 2021 ). Supplementation of K + or chelated K + in feeds resulted in a minor improvement in fish and shrimp growth ( Saoud et al, 2007 ).…”

“…Reclamation of a vast land of around 380 million ha ( Lambers, 2003 ) through aqua-farming has immense potential for enhancing the expansion of aquaculture activities and production, livelihood generation and minimizing rural migration besides restoration of ecological balance ( Allan et al, 2009 ). However, the potential use of inland saline water (ISW) for aquaculture has a significant limitation due to its sub-optimal ionic composition compared to seawater ( Allan et al, 2009 , Booth and Fielder, 2016 ). Despite variation in the composition of ISW across locations, most inland saline groundwater is deficient in potassium ( Allan et al, 2009 ).…”

“…Potassium is the most abundant intracellular ion, playing crucial roles in osmotic, ionic, and acid-base regulations in aquatic animals ( Booth & Fielder, 2016 ). Multiple shreds of evidence suggest that K + deficient groundwater causes morbidity and mortality of euryhaline/marine species, such as barramundi ( Lates calcarifer ), snapper ( Pagrus auratus ), mulloway ( Argyrosomus japonicas).…”

“…Multiple shreds of evidence suggest that K + deficient groundwater causes morbidity and mortality of euryhaline/marine species, such as barramundi ( Lates calcarifer ), snapper ( Pagrus auratus ), mulloway ( Argyrosomus japonicas). The fish exhibit nearly optimal growth when the K + of water remains above 60 % of equivalent salinity seawater concentrations ( Booth & Fielder, 2016 ). K + fortification through the addition of muriate of potash (KCl) and K-Mag for maintaining seawater equivalent K + in inland saline aquaculture has been accepted globally.…”

“…Studies on dietary supplementation of K + for maintaining ionic homeostasis and typical growth performance in fish are rare and contradictory. Shearer (1988) reported that juvenile Chinook salmon benefitted from dietary supplementation of K + when reared in freshwater, whereas K + in feed does not ameliorate the adverse effects of K + deficient saline groundwater on the survival of juvenile snapper ( Booth & Fielder, 2016 ). However, fortifying water or diet with K + ensures penaeids culture suitable in potassium deficient groundwater ( Gong et al, 2004 ).…”