Recreational water

Community and Public Health is involved with the quality of coastal waters and freshwater waterways which are used for a range of recreational activities such as swimming, sailing, boating, surfing, water skiing, underwater diving and shellfish gathering.

The quality of recreational water is an important environmental health and resource management issue.

Marine biotoxin warning for Banks Peninsula

Canterbury DHB media release: 5th June 2020

Community and Public Health has issued a health warning advising the public not to collect or consume shellfish harvested from between Sumner Head and East Head at Okains Bay on Banks Peninsula, including Lyttelton Harbour.

Canterbury Medical Officer of Health Dr Anna Stevenson says routine tests on shellfish samples taken from Port Levy have shown levels of diarrhetic shellfish poisoning toxins above the safe limit.  Anyone eating shellfish from this area is potentially at risk of illness.

“Mussels, oysters, tuatua, pipi, toheroa, cockles, scallops, catseyes, kina (sea urchin) and all other bivalve shellfish should not be eaten.”

Dr Stevenson warns that cooking shellfish does not remove the toxin. “Symptoms of diarrhetic shellfish poisoning typically appear within half an hour and can last for 24 hours.”

Symptoms of diarrhetic shellfish poisoning may include:

  • Diarrhoea;
  • Vomiting;
  • Nausea; or
  • Abdominal cramps.

Dr Stevenson says pāua, crab and crayfish may still be eaten if the gut has been completely removed prior to cooking, as toxins accumulate in the gut. Not removing the gut could contaminate the meat during the cooking process.

Phone your usual General Practice team 24/7 if anyone becomes ill after eating shellfish from an area where a public health warning has been issued. They can advise you what to do and where you can receive care if required. Phone 111 if it’s an emergency.

“You are also advised to contact Community and Public Health on 03 364 1777 and keep any leftover shellfish in case it can be tested,” says Dr Stevenson.

MPI will continue to monitor toxin levels and any changes will be communicated accordingly.

Health Risks Associated with Contaminated Water

Underwater view of water in New Zealand river looking up from the river bed. Source: LAWA.Water can be contaminated by human or animal excreta (poo) containing disease causing micro-organisms such as viruses, bacteria and protozoa.

Contamination poses a health hazard when the water is used for recreational activities such as swimming and other high contact water sports.

There is a risk that water will be swallowed, inhaled or come into contact with ears, nasal passages, mucous membranes or cuts in the skin, allowing pathogens or algal toxins to enter the body.

The symptoms of exposure to contaminated water are usually minor and short lived, however there is the potential for more serious diseases including hepatitis A, giardiasis and cryptosporidiosis.

Health Risks associated with Algal Blooms

Algal blooms are appearing more frequently in our waterways. Algal blooms in lakes can be blue/green in colour floating on the surface or colourless globules suspended in the water.

Algal blooms are also found in rivers as blackish benthic mat-forming cyanobacteria clinging to rocks or collecting at the riverbank. Some cyanobacteria species are known to produce toxins.

Symptoms of exposure to toxic algae can range from allergic reactions, asthma, eye irritations, and rashes to rapid onset of nausea and diarrhoea to gastroenteritis to other specific effects such as liver damage and possibly developing cancers.

Health Risks associated with Mahinga kai

Water containing micro-organisms, chemicals, phytoplankton or cyanobacteria can pose a risk to health through recreational contact, drinking and gathering mahinga kai.

Mahinga kai species associated with water are fish (including tuna and inanga), kanakana shellfish (such as mussels, oysters, scallops, tuangi and tuatua) as well as seaweed and watercress.

Responsibility for Monitoring Water Quality

Regional councils like Environment Canterbury coordinate the monitoring of the various sites throughout our region and inform Community and Public Health and the territorial local authority (TLA) if contamination levels present a potential health risk.

The Territorial Local Authority places warning signs to inform the public where a health risk is identified, and takes steps to remove the contamination if possible.

Community and Public Health supports the TLAs in advising the public of the risk and ensuring that they deal with the contamination appropriately.



Download or order resources from the Community Health Information Centre.


Contact your local CPH office for further information:

Ph: +64 3 364 1777
Fax: +64 3 379 6125

Ph: +64 3 687 2600
Fax: +64 3 688 6091

Ph: +64 3 768 1160
Fax: +64 3 768 1169

For additional information or to report water pollution, contact:

Environment Canterbury Pollution Hotline
Ph: 03 3664 663 or
0800 765 588

West Coast Pollution Hotline
Ph: 0508 800 118

Toxic algae present in some Canterbury waterways

Updated 22nd June 2020

All recreational water users are being reminded to avoid contact with some Canterbury and South Canterbury waterways. Recently added warnings are highlighted in bold.

Potentially toxic algae is currently present in the following locations in the region:

  • Lake Ellesmere/ Te Waihora
  • Lake Forsyth/ Te Roto o Wairewa
  • Lake Rotorua (Kaikoura) – this is a permanent warning

Find out more about the public health risks of toxic algal blooms [161KB PDF].

Visit the Environment Canterbury website for more information on water health warnings. Routine monitoring of waterways for summer runs from November to March each year.

LAWA: Land Air Water Aotearoa.

Page last updated: 24/06/2020

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