A foul smelling odour is wafting up from Tilba Lake while dead bream have surfaced in Kianga Lake. So what’s going on with these small estuary lakes in the Narooma district?
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
Former commercial fisherman, ex Water Board employee and marine biologist, Ron Snape of Tilba, has been watching the Intermittently Closed and Open Lakes and Lagoons (ICOLLS) for years and has his theories.
In a nutshell, the hot and dry weather experienced lately on the Far South Coast has had an impact on these waterways and is part of an ongoing natural cycle.
The subject of dying lakes and fish kills came up at the recent meeting called by the Environment Protection Authority and Eurobodalla Shire Council for stakeholders to discuss the waterways adjacent to the Brou landfill and what reasons for their poor health. Read more
The local Fisheries officer attending that meeting encouraged anyone noticing fish kills and dying lakes to contact the department through the Fishers Watch phoneline on 1800 043 536.
Retired Narooma science school teacher Graham Sawyer did just that when he noticed dead bream, some of a rather large size, in Kianga Lake earlier this month. Fisheries and the council, who operates a sewerage treatment plant adjacent to the lake, did their inspections.
Tilba Lake meanwhile seems to be in even worse shape with a foul smelling odour wafting up onto neighbouring properties and as far as the hamlet of Mystery Bay.
Mr Snape said Tilba, Kianga and Barragoot lakes periodically die off when they come under stress from prolonged dry periods The salinity rises due to evaporation, and during a real hot day Tilba can dry off up to 70mm a day.
“The lake usually dies after a very hot day followed by a southerly change,” Mr Snape said “I think the lakes are at their maximum productivity just before they die.
“It’s rather clear that the biological oxygen demand exceeds biological supply. This only needs to happen for only a minute or two to start the die off.
“Then we have the aerobic decay process taking place. That is the decay of organic material with the use of oxygen in the water thus taking more oxygen. Fish tend to beach themselves for the only oxygen left in the water is in very shallows.”
Mr Snape said in Tilba Lake as the waterway dried up earlier this year, there was literally 50 or 60 meters of shoreline with dead pink nippers so many the gulls could not keep up with them coming to the surface.
“The school prawns went next, and I got about a kilo for bait before the gulls got them,” he said.
“With the lake under so much stress the pelicans had a field day. There were over 300, I guess, now there is very few. This tells the story.”
Even a large mud crab that made the Narooma News fishing report and was released by this journalist and later spotted by Mr Snape and also allowed to swim free, was no doubt dead, along with all the other blue swimmer crabs and octopus.
“There are still a few bream and mullet down at the sandbar when the high tide still comes in through the sand,” he said. “I was at the mouth two days ago not a pretty sight or smell.
“The same black slimy sludge as per Brou Creek, but the slime in Tilba Lake comes from the decay of the green weed rotting.”
Mr Snape went on to theorise that when there is fish kill in Tilba and the other small shallow lakes, it is usually complete.
“We can have several die in dry event. There can literally be 10s of tonnes of dead fish mullet, bream blackfish and the like and all the crustaceans and the food chain that supports our recreational and commercial species dead,” he said.
“The rebirth of the lake occurs when the lake opens although weeds and smaller crustaceans could well be transported in via birds.”