Environment Southland (ES) are recommending Mataura River water users, including fisherman, to take extra precautions after high levels of potentially toxic algae in the Mataura River at the Mataura Island Bridge

Contact with water and the algae, including swimming in the Mataura River near Mataura township should be avoided.

However while fish caught in the river may be eaten, this should only be done occasionally - less than once a week.

ES advise fish may taste earthy due to other compounds produced by the toxic algae. There is no relationship with taste and the concentration of toxins, they said.

Other recommendations for fisherman include:

• Wearing clothing such as waders to minimise contact with the water
• Washing your hands and any other skin that’s been in contact with the river with clean water and soap. Use of hand sanitiser may not remove all the algae from the skin, so clean, running water is best for washing hands and skin.
• Avoid eating the liver and other organs, as this is where the accumulation of toxins may be greatest.

Algae occur naturally in waterways and can flourish during fine conditions and periods of stable river flows.

Most algae are harmless, however, some cyanobacteria can produce toxins and rapidly bloom to high levels.

These algae are potentially toxic and can be commonly identified in waterways as a dark green/brown slime on rocks, or dark brown/black mats at the water’s edge.

The toxins these algae can produce are harmful to people and animals if swallowed, or through contact with skin.

People should keep dogs on a lead and children away from affected waterways. The public is urged to be mindful of the potential health risks waterways with toxic algae alerts may pose, until health warnings are removed.

If you experience health symptoms after contact with contaminated water, visit a doctor immediately.

If you are concerned that any animals have consumed toxic algae or contaminated water, they should be taken to a vet immediately.

ES monitors toxic algae monthly at a number of rivers and lakes across Murihiku-Southland.