Fish are dying in Hawke's Bay streams that are heating up in the relentless summer sun.
Hawke's Bay Regional Council scientist Dan Fake said as river levels get low and water temperatures rise freshwater fish can be stressed.
"Many of our native freshwater fish prefer temperatures around the 20C, so when in-stream temperatures are pushing 29C like they have been in the past couple of weeks, we start seeing cases of infection in fish and even fish dying," Fake said.
"Trout also don't do well in warm temperatures, and it's not uncommon to find sick or dead trout at this time of year," he said.
Low river levels can also cause river mouth blockages. When a swell moves gravel there sometimes isn't enough water flow in the river to remove it.