Survival and growth of Australian snapper, Pagrus auratus, in saline groundwater from inland New South Wales, Australia

Abstract

Australia has extensive resources of inland saline groundwater, which may be suitable for culture of marine fish. This study assessed the suitability of saline groundwater, which was pumped from a shallow aquifer into an evaporation pond near Wakool in western New South Wales, for growth and survival of juvenile snapper, Pagrus auratus. Five experiments were conducted. The first showed that snapper (31 g) did not commence feeding, lost equilibrium of buoyancy and became moribund within 3 days after transfer from coastal seawater (diluted to 19‰ with rainwater) to saline groundwater (19‰). Potassium concentration of diluted coastal seawater and groundwater (both 19.6‰) was 203 and 9.2 mg l −1, respectively, while the concentration of most other major ions was similar in water from both sources. In the second experiment, groundwater of 21‰ salinity was fortified with potassium (as KCl) to provide 25%, 50% or 100% of the concentration of potassium found in coastal seawater of 21‰ salinity. Survival and feeding and swimming behaviour of snapper (1.5 g) held in tanks for 8 days were the same in 50% and 100% potassium-fortified treatments as in coastal seawater controls. However, snapper held in groundwater fortified with only 25% potassium, or raw saline groundwater became moribund after 4 and 2 days, respectively. During the third 42-day experiment, growth, survival and food conversion of juvenile snapper (4.0 g) were the same in diluted coastal seawater (20‰) and groundwater (20‰) provided the level of potassium in the groundwater was increased to within 60–100% of the concentration in coastal seawater. During the fourth experiment, juvenile snapper were acclimatised to raw saline groundwater by transferring fish from fortified groundwater with initial potassium levels of 100% of that in coastal seawater, to groundwater with 10% lower potassium levels every 3.5 days or 20% lower levels every 7 days. A further treatment where snapper were transferred from groundwater fortified initially with potassium levels of 60% of coastal seawater, to groundwater with 20% lower potassium levels every 3.5 days was included. When potassium was reduced to 20% of the concentration in coastal seawater, in all treatments, fish became moribund. Results from the fifth experiment, where groundwater was fortified with either KCl or NaCl at equivalent chloride levels, confirmed that potassium and not chloride ions were responsible for improvement in groundwater. Our results demonstrate that saline groundwater from Wakool, fortified with KCl is a suitable medium for growing snapper juveniles in tanks.