Green growth in Hastings stream not cause of fish deaths

The green surface growth on the Awahou Stream in Hastings is lemna disperma. Photo / Chris Hyde

Hawke's Bay Regional Council says a bright green stream near to where roughly 20 dead fish were found last week is healthy.

About 20 perch and goldfish were found dead, floating in a pond downstream of the Hastings Top 10 Holiday Park last week, and on Monday the stream was photographed near Splash Planet carpeted by a bright green growth.

Hawke's Bay Regional Council group manager policy and regulation Katrina Brunton said compliance staff visited the stream to do tests on the green growth.

She said the team identified the growth as the indigenous plant species, lemna disperma and found that area of the stream to be full of fish life.

"It does not represent a risk of toxicity, but abundant growth of lemna is often indicative of nutrient-rich and slow-flowing conditions," she said.

Brunton said they would not be investigating the exact cause of the deaths of the non-native fish species.

Dead fish were found in the Awahou Stream, near Splash Planet, in Hastings. Photo / Warren Buckland.

Brunton said there were many reasons why they may have died.

"Often in these kinds of cases, it is an expensive and unproductive effort to pinpoint the cause," she said.

HBRC's water quality testing of the Awahou Stream showed the water to be clear, at a regular temperature, with no sign of any toxins or poison.

"Fish don't exhibit too many diagnostic symptoms and so investigations are more often inconclusive than productive."

Brenton said the council was focused on improving the health of the region's waterways through policy, so that events like this become less frequent.