McMurtrie, S. (2012, July). Heavy metals in fish and shellfish: 2012 survey. EOS Ecology.

Funded by Environment Canterbury (ECan) in 2012, this report contributed to the “Food Safe to Eat” component of the “Healthy Estuary and Rivers of the City” programme established by ECan, Christchurch City Council (CCC), and the Avon-Heathcote Estuary Ihutai Trust. Heavy metals from urban, agricultural, and industrial land use often flow directly into rivers and estuaries via stormwater networks. Once there, heavy metals can accumulate in sediments to levels highly dangerous to both humans and other organisms. The purpose of this report was therefore to monitor heavy metal pollution by measuring the concentrations of different metals in fish and shellfish within the Ihutai catchment. The report measured mercury, lead, cadmium, and arsenic, and was especially important for identifying the danger associated with people eating seafood from the Ihutai estuary.

Overall, the results reflected impacts of sewage discharge into the estuary from the 2010-11 Canterbury earthquakes. Although cockles, pipi, shrimp, yelloweye mullet, sand flounder, shortfin eels, and whitebait species all had metal concentrations below the 2008 FSANZ limits, the report still expressed concern regarding the consumption of shellfish from the estuary due to potential faecal contamination from sewage, wildlife, or dogs. It expressed hope that viral and bacterial levels in estuary shellfish would drop once Christchurch City repaired its badly damaged sewage infrastructure.