OTHER POLLUTION (heavy metals, organic poisons and bacteria)
Pollution from heavy metals, other chemicals, and bacteria can affect nearshore fisheries.
Heavy metals and other chemicals seem less of a problem in New Zealand than in some places overseas. Monitoring conducted by regional councils has shown heavy metals like zinc and lead in some of our upper estuarine areas close to some New Zealand cities. More work needs to be done, but evidence from both overseas and New Zealand suggests such build-ups can change the structure of seabed communities.
Disease-causing micro-organisms like bacteria and viruses can have a huge effect on our use of coastal fisheries. These micro-organisms get flushed off the land and city streets during heavy rainfall, and end up in coastal waters. They can also enter coastal waters through poorly-maintained septic tanks and sewage discharge from recreational boats.
Shellfish like mussels, oysters, cockles, pipi and tuatua filter out and concentrate these bacteria or viruses in their stomachs. If people then eat these shellfish raw, it can make them very sick. After a number of days, these micro-organisms will pass through a shellfish’s digestive system. Once this has happened, the shellfish become safe to eat again.