Keeping dogs safe from potentially toxic algae

Dog in riverbedPotentially toxic algae (also called cyanobacteria) can make animals extremely sick when ingested. In some cases, it can also cause death.

Unfortunately, dogs love the musty smell of potentially toxic algae and are naturally drawn to investigating it – usually by licking or ingesting the material when out enjoying rivers and lakes across the country.

Even if a small amount (the size of a 50 cent piece) of potentially toxic algae is ingested, it can be harmful to your dog.
Knowing what to look for when visiting Canterbury’s freshwater sites is the best way to keep your dog safe.

How to spot potentially toxic algae/cyanobacteria

Not all algae in our rivers and lakes are harmful but it’s not easy to tell the difference.

If you are in any doubt about the water quality, then keep your dog on a leash and away from the water, and water’s edge.

In rivers

This cyanobacteria (called benthic cyanobacteria) grows on the bottom of river beds. It appears as thick dark brown or black mats that have a slimy or velvety texture and musty smell.

Cyanobacteria in riverbed
Cyanobacteria on rocks

In lakes, ponds and lagoons

Planktonic cyanobacteria (floating algae) is often suspended in the water. When it blooms, it can make water look cloudy, discoloured, or like it has small globules in it. There may not be obvious visual traits.

Cyanobacteria in lake
Cyanobacteria in pond

Caution advised at these Canterbury rivers

Potentially toxic algae (cyanobacteria) are known to grow in these rivers and may pose a risk to dogs - please be cautious and ensure you check the area for potentially toxic cyanobacteria when visiting: Rakahuri / Ashley River, Waikirikiri / Selwyn River, Opihi River, Otaio River, Pareora River, Temuka River, Waiau River. Waipara River, Waihao River, Waihi River, Waimakariri River, Leader River and Waitohi River.

Monitored swimming spots along these rivers may not have an active public health warning. This is because the amount of potentially toxic algae is below the threshold for a public health warning - view current health warnings.

Know the symptoms of poisoning

If your dog is showing these symptoms after being in contact with a waterway, contact a veterinarian immediately. You or your vet can report any animal illness resulting from contact with cyanobacteria to us.

  • panting
  • lethargy
  • muscle tremors
  • twitching
  • convulsions.

In extreme cases, death can occur 30 minutes after symptoms first appear.

LAWA Can I Swim Here

We monitor water quality at some of the region’s recreational swim sites between November and March. However, we cannot monitor all sites and water quality results on Land Air Water Aotearoa (LAWA) and health warnings are based on the risk to human health, not dog.

Find out more