Dead eels at Lake Tutira this week. Hawke's Bay Regional Council is investigating.
© Stevie Smitd/HBRCDead eels at Lake Tutira this week. Hawke's Bay Regional Council is investigating.
Another fish kill at troubled Lake Tutira in Hawke's Bay has authorities concerned.

About 20 dead or dying eels were found, and there were reports this week of dead trout at the lake, about 40 kilometres north on Napier.

It is the second time this year that a major die-off has been detected.

In January, trout and eels died en masse in an event thought to be linked to low levels of dissolved oxygen in the lake's surface water.

"Fish kills have not been uncommon. However, the occurrence of two large fish kills in two consecutive years is unusual and of particular concern," Hawke's Bay Regional Council said on Thursday.

Another victim at Lake Tutira this week.
© Stevie Smitd/HBRCAnother victim at Lake Tutira this week.

"I went up yesterday and saw about 20 dead or dying eels," environmental scientist Andy Hicks said.

"The dead eels are very obvious to any visitors who approach the shore, with dead or dying fish observed around the boat ramp, camping grounds and northern end of the lake.

"There was a slight stink in the air."

He said regional council staff recorded a pH or acidity level of up to 9.4 at the boat ramp.

"Any reading above 9 is extreme...But unlike last year, the monitoring buoy in the lake has not recorded any periods of extremely high temperature or low dissolved oxygen around the times of this fish kill."

Regional council staff saw many common bullies, small native fish, thriving in the shallows of Lake Tutira and nearby Lake Waikopiro.

A Department of Conservation campsite is beside the freshwater lake.

Unsafe to safe

Hicks said visitors should not touch any dead fish, which were not safe for humans or pets to eat.

Dead eels have been sent to Cawthron Research Institute for autopsies, and water samples sent for laboratory analysis to measure nutrient levels and algae presence.

The results might not be received till the New Year.

This time last year, HBRC declared the lake unfit for swimming, boating or kayaking.

In 2009, people were told not to swim in Lake Tutira after cyanobacteria algal blooms were discovered.

In 2008, the lake was infested with hydrilla, a highly invasive water weed which the Ministry for Primary Industries considered "one of the world's worst."

HBRC said it was working with Maungaharuru-Tangitu Trust to improve lake water quality.

University of Waikato lake restoration specialists were also hired to work on a computer modelling project to find solutions for the lake's ecological crises.