Congo resident Jayne Clark was walking her dog in the morning when she noticed a lot of fish at the waters-edge flapping around with their mouths open.

Realizing they were probably starved for oxygen, she went home and called a couple of friends asking them to bring a bucket and help get some of the distressed fish to the ocean.

They spent several hours taking buckets of fish by car down to the ocean.

“As soon as they hit the ocean, most of them swam straight away, though a few still died,” Jayne said.

By 12 o’clock all the fish left in the creek were dead.

Richard Wood and his wife Chrissy from Corunna near Narooma were camping at the Congo Camping ground and on Wednesday had kayaked about one and a half kilometres up Congo Creek.

“We were on the northern side of the creek and there were loads of dead fish,” Richard said.

“There was evidence of dead fish further up-stream and a curious slightly nauseating smell,” he said.

A spokesperson from the Department of Primary Industries (DPI) said that Marine Park officers inspected the area in the vicinity of the Congo playground and confirmed that there had been a ‘minor’ fish kill.

“Hundreds of freshly dead and dying bream, mullet, flathead, garfish, whiting, sole, juvenile mud crabs and luderick were observed along the water’s edge and floating in the water.

“Local residents reported a lot of weed floating at the water’s edge over preceding days and the water was discoloured at the time of inspection, but there was no obvious smell,” the spokesperson said.

The Department of Primary Industries said the suspected cause is localised low levels of dissolved oxygen (DO).

Very low levels of DO will cause suffocation and death of aquatic animals.

There are a number of variables that can contribute to the de-oxygenation of water including excessive plant growth, floods and black water.

On Sunday night Congo received about three inches of rain and there was evidence on Wednesday of run off into the creek that contained evidence of ‘black water’.

The black water is usually discoloured because of the high levels of dissolved tannins and lignin from decomposed organic matter.

Although fish kills can occur at any time of the day and in any month of the year data indicates that they are more likely to occur in summer during January and February because of higher water temperatures and storm events that lead to lower dissolved oxygen levels.

The site was posted with a No Swimming – Health Hazard sign by Eurobodalla Shire Council.

Over the last six years there have been fish kills reported in Wallaga Lake, Corunna Lake, Barragoot Lake and Nangudga Lake.