The suspected cause of up to 100 fish deaths in Bonny Hills is low dissolved oxygen level, according to the NSW Department of Primary Industries (DPI).
Bonny Hills resident Jack Orafferty took a number of photos on Monday, June 10 at Duchess Creek in Bonny Hills.
The photos captured a number of dead marine animals, including eels and fish.
Jack said both Duchess Creek and Little Vinegar Creek have had a strong smell for days, particularly Friday when the water was very cloudy.
The NSW DPI and Port Macquarie Hastings Council investigated a report of fish deaths at the Duchess Creek location on Friday, June 7.
"There are many and varied causes that influence fish health and unfortunately fish deaths," a spokesperson from NSW DPI said.
"A large proportion of fish deaths are due to natural events."
Community members are encouraged to report any similar incidents or observations through the Fishers Watch hotline on 1800 043 536.
For more information visit www.dpi.nsw.gov.au
The news at Bonny Hills comes after a Camden Haven High School excursion into the waterways at Lake Cathie and Lake Innes uncovered disturbing results.
The students found high salinity levels and dead fish, painting a dire picture of a starving marine environment.
Meanwhile Revive Lake Cathie is planning a meeting with all stakeholders to help future-proof the lakes.
"Revive Lake Cathie is working towards providing conditions suitable for a sustainable ecological system by seeking implementation of historical report recommendations," Revive Lake Cathie board member Cara Dale said.
Revive Lake Cathie is calling for council to adopt the Revive Lake Cathie submission into its 2019-20 operational plan on June 19 at its monthly meeting. A contingent from the action group will attend the meeting which starts at 5.30pm.