Environmental effects of yellowtail kingfish aquaculture in South Australia

The culture of yellowtail kingfish Seriola lalandi in South Australia is one of the most rapidly growing aquaculture sectors in Australia. To date, there is a paucity of information on the environmental impacts of this industry, due to its relatively small size in comparison to other industry sectors. Here, we report on a study examining the response of a range of environmental variables to yellowtail kingfish aquaculture in Fitzgerald Bay, northern Spencer Gulf, South Australia. The clearest response occurred in several chemical variables, with an 81% increase in ammonia concentrations adjacent to cages relative to controls, increased sediment organic carbon (7 to 46%) and increased porewater phosphorus in the sediments (80 to 3077%). While there were also statistically significant effects on infaunal and epifaunal assemblages, results for both groups were equivocal because of high small-scale variability. For the infauna, assemblages at the sites furthest from cages tended to be similar to those adjacent to cages, while those at intermediate distances differed. No impacts were detected on phytoplankton, or on seagrasses (although the latter only occurred >250 m from any aquaculture cage). The lack of clear responses in the biotic datasets is probably related to the relatively low production levels (<2000 t yr–1 at the time of the study), although the responses in the chemical variables provide a valuable early warning as production increases.