Authorities are investigating after dozens of dead fish were found washed up at several of the Hunter's southern beaches this week.
A large number of fish were spotted on Merewether Beach on Tuesday, with more also reported at Dudley and Redhead.
Hamilton Child Care Centre educator Bannaua Brown was on an excursion at Merewether Beach to teach the children about caring for the environment by "taking three (pieces of rubbish) from the sea", when they stumbled upon the scaly scene.
"It was on a short stretch of beach in front of the surfhouse," she said. "There were probably 100.
"It wasn't just one kind of fish."
Ms Brown said they buried some of the fish under the sand. The children were "fascinated" by what they saw and wanted to know how it happened, she said.
A NSW Department of Primary Industries spokesperson said they were aware of a reported fish death event at Dudley, Merewether and Redhead beaches this week and investigations were ongoing.
The department's website details information about fish kills, which are defined as a "sudden mass mortality of wild fish".
It says they "can occur at any time although data indicates fish kills are more likely to occur in summer or following sudden changes in temperature".
"Community members are encouraged to report any fish deaths or observations through the Fishers Watch Phoneline on 1800 043 536," the department spokesperson said.
It comes after two mass fish kills were also reported in Lake Macquarie around Mannering Park in recent months.
