Greenwood, M. (2008, June). Metal concentrations in fish and shellfish of the Avon-Heathcote Estuary/Ihutai and rivers: 2008. EOS Ecology.

Funded by Environment Canterbury (ECan) in 2008, 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 and metaloids like cadmium, lead, copper, zinc, and arsenic tend to accumulate in soil and water. They enter our rivers and estuaries via runoff from industry, urban, and agricultural land use, and at high concentrations, are detrimental to human and ecosystem health.

Because marine and freshwater organisms accumulate contaminants from their environment, they can be used to monitor heavy metal pollution. Seafood with high heavy metal concentrations can be dangerous to consume, therefore, the New Zealand Food Safety Authority (FSANZ) sets safe concentration limits. In 2008 there were many signs warning against eating shellfish from the Ihutai estuary. This research report aimed to measure the concentrations of metals in estuary fish and shellfish to determine whether they were safe to eat. Overall, they found that cockles, pipi, yelloweye mullet, sand flounder, and shortfin eels all had metal concentrations below the 2008 FSANZ safe consumption limits. However, they still advised caution for those collecting fish and shellfish from Te Ihutai, as potentially high levels of E. coli bacteria could still make people sick.