Metabolic and osmregulatory responses of snapper (Pagrus auratas), Mulloway (Argyrosomus japonicus) and yellowtail kingfish (Seriola lalandi) in saline groundwater

Australia has an abundance of saline groundwater due to land clearing and irrigation within the Murray-Darling river system. Generally saline groundwater contains similar ions to coastal seawater with concentrations varying due to the source of the water. In this study Australian snapper (Pagrus auratus), mulloway (Argyrosomus japonicus) and yellowtail kingfish (Seriola lalandi) were chosen to examine their suitability for culture in saline groundwater. The growth and metabolic response of the aforementioned species were investigated to determine their suitability for culture in saline groundwater from the 'outfall' of the Stockyard Plains Disposal Basin (SPDB) in Waikerie, South Australia (potassium ~ 80 mg.L-1). In the first experiment snapper, mulloway and yellowtail kingfish were cultured in saline groundwater (salinity = 19 ± 1 g.L-1), half-strength coastal seawater (iso-osmotic; 19 ± 1 g.L-1) and oceanic seawater (except snapper; 37 ± 1 g.L-1) for 61, 45 and 21 days respectively, to determine survival, growth rate and food conversion ratio. At the end of each growth experiment, fish were placed in static box respirometers to record changes in oxygen consumption in the different water types. Changes in oxygen consumption were used as an indirect method to determine routine metabolic rate (Mo2rout), maximum metabolic rate (Mo2max) and metabolic scope (Mo2scope). In the second experiment, blood samples were taken from the fish 1 hour postexhaustion and analysed for blood plasma sodium, potassium, chloride, lactate and osmolality to determine if fish were able to cope with osmoregulatory changes.