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

Australia has extensive resources of inland saline groundwater, which may b e suitable for culture of marine fish. This study assessed the suitability of saline groundwater, which was pumped from a shallow aquifer into an evap oration pond near Wakool in western New South Wales, for growth and surviva l of juvenile snapper, Pagrus auratus. Five experiments were conducted. The first showed that snapper (31 g) did not commence feeding, lost equilibriu m of buoyancy and became moribund within 3 days after transfer from coastal seawater (diluted to 19 parts per thousand with rainwater) to saline groun dwater (19 parts per thousand) Potassium concentration of diluted coastal s eawater and groundwater (both 19.6 parts per thousand) was 203 and 9.2 mg l (-1), respectively, while the concentration of most other major ions was si milar in water from both sources. In the second experiment, groundwater of 21 parts per thousand salinity was fortified with potassium (as KCl) to pro vide 25%, 50% or 100% of the concentration of potassium found in coastal se awater of 21 parts per thousand 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. H owever, snapper held in groundwater fortified with only 25% potassium, or r aw saline groundwater became moribund after 4 and 2 days, respectively. Dur ing the third 42-day experiment, growth, survival and food conversion of ju venile snapper (4.0 g) were the same in diluted coastal seawater (20 parts per thousand) and groundwater (20 parts per thousand) provided the level of potassium in the groundwater was increased to within 60-100% of the concen tration in coastal seawater. During the fourth experiment, juvenile snapper were acclimatised to raw saline groundwater by transferring fish from fort ified 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 trans ferred 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 Na Cl at equivalent chloride levels, confirmed that potassium and not chloride ions were responsible for improvement in groundwater. Our results demonstr ate that saline groundwater from Wakool, fortified with KCl is a suitable m edium for growing snapper juveniles in tanks. (C) 2001 Elsevier Science B.V . All rights reserved.