A disturbing video shows fish gasping for oxygen in Lake Ngaroto, a Waikato lake near Te Awamutu.
The video, posted to a local community page, shows dozens of dead fish washed up on the shoreline of the lake. Others gasp helplessly at the surface where oxygen levels are highest.
"That's weird bro, something's going on there aye," one person says in the footage, as the camera moves over the dying school.
"OMG it is going to stink so bad there soon in this heat. The poor fish and eels. Devastating for them," one person commented.
According to the Waikato Regional Council's website, Lake Ngaroto has poor water quality with monitoring showing very high levels of nutrients, high levels of algae and high levels of suspended sediment.
"Our scientists advise that this lake often has 'health warnings' issued by the DHB for recreation due to the large toxic algae blooms every summer," a spokesperson told Newshub.
"The latest results from December 20 2021 show a large algae bloom is building and the lake is currently at 'caution advised' status.
"On these hot summer nights during algal blooms, the oxygen concentrations in the lake drop too low for the fish, and it can lead to very hardy fish 'gasping' at the surface and/or mass fish kills.
"Also, the algae can release toxins that can cause large-scale fish deaths."
A restoration project started by the Waipa District Council in 1995 has now seen the lake boundary fenced and over half the lake edge planted. Sediment and nutrient traps have also been constructed to help the lake's recovery.