Fish farming
Northern Spencer Gulf is an oligotrophic inverse estuary with naturally low levels of nutrients cycling through it. A potential exists for anthropogenic nutrient pollution to cause eutrophication in the region with associated ecological impacts to the cuttlefish and wider ecology. A long-term industrial nutrient pollution source exists to the west of the cuttlefish breeding reef at the Whyalla steelworks. There, ammonia, a byproduct of its coking process for steel-making, and is discharged into Spencer Gulf via reed-beds and settling ponds. North of the cuttlefish aggregation, sea cage farming of yellowtail kingfish occurred commercially from the late 1990s until 2011. Fish farming is another nutrient pollution source, as uneaten feed and fish waste enter the water column and sediment. Concerns have been raised about an observed correlation between fish farming intensification, fish mortalities and the decline and eventual recovery of the giant Australian cuttlefish after fish farming ceased in upper Spencer Gulf.