PAST RESEARCH AND BARRIERS TO COMMERCIAL AQUACULTURE UTILISING SALINE GROUNDWATER FROM SALT INTERCEPTIONS SCHEMES IN SOUTH AUSTRALIA

saline groundwater although considerable past research has investigated the use of these resources for aquaculture. Substantial salinity increases occur along the course of the Murray River within South Australia. To reduce this salt input, salinity interception schemes comprised of lines of bores either side of the river operate to pipe intruding saline groundwater to land locked salt disposal basins. These schemes intercept ~ 500 tonnes of salt per day. Between 2005 and 2008 the Waikerie Inland Saline Aquaculture Research Centre (WISAC) was designed and constructed to investigate the potential use of saline groundwater from the Woolpunda and Waikerie salt interception schemes that intercept approximately 30 ML of saline groundwater per day (~350 tonnes salt day-1). Water available from this scheme (350 Ls-1) has relatively constant water temperature between 20-22oC and a salinity of 18 - 20 gL-1. Potassium concentration varied between 80-100 mgL-1 (36.4% – 45.5% of the level of equivalent salinity seawater).

Trials conducted at the South Australian Aquatic Science Centre showed no significant differences in growth, food conversion ratio or specific growth rate for Mulloway (Argyrosomus japonicus) cultured in saline groundwater, diluted seawater or seawater. Research at WISAC demonstrated that although Mulloway cultured using saline groundwater exceed growth of fish in sea cages and the wild, they did not achieve the growth rate expected for fish cultured in the optimal water temperatures provided. This was most likely due to the elevated level of dissolved CO2. Dissolved CO2 levels of 50-70 mgL-1 were present in incoming saline ground water that was reduced to an average of 10.7 mgCO2L-1 (SD ± 1.8 mgCO2L-1) by degassing prior to use. Research at WISAC showed that Mulloway grown in 6 mgCO2L-1 grew significantly better than fish grown in 10 mgCO2L-1 and 20 mgCO2L-1 which grew significantly better than fish cultured in 40 mgCO2L-1. From May 2006 until March 2008, 9.8 tonnes of Mulloway were harvested and fish and system performance data were collected.

Barriers to commercialisation of aquaculture identified include:

• High concentration of dissolved CO2 in groundwater means that culture systems need include effective technologies to reduce CO2 as low as possible (<10 mgCO2L-1).
• Water composition of groundwater from salt interception schemes limits the range of species that can be cultured without supplementation of deficient elements.
• Uncertainty of water supply. Salt interception schemes have been turned off during recent Murray River floods. Commercial ventures need system capabilities and contingency arrangements to be developed in advance of these events.
• High cost of pumping discharge water back into the interception scheme pipe. A location close to Stockyard Plain disposal basin may allow drainage into the basin.
• Stockyard Plain disposal basin has become a recognised wet land system. This may require additional water treatment prior to discharge.