A potentially large number of dead fish may become a regular sight in the lake at Forest Lake this winter, however the community can rest assured there is no need to be alarmed.
Forest Lake Ward councillor Charles Strunk says among other species, the lake has a very large population of invasive pest “Tilapia” fish who cannot survive in cold conditions.
It is not uncommon for Tilapia fish to die in the lake during Brisbane’s cold snaps during the winter months.
“This is a Middle Eastern Nile species that has found their way into our environment via fish tanks,” Cr Strunk said.
“A couple of years ago we had a fish kill-off of about 400 fish, and all but about three of them were Tilapia.”
Brisbane City Council removed about 400 kilograms of dead Tilapia from the lake at the time and conducted tests in the water to identify the cause.
“These fish are coming from more temperate parts of the globe where the water doesn’t get as cold as it does here,” Cr Strunk said.“
What had happened is the temperature of the water of the lake dropped to the point where the Tilapia fish died.”
Cr Strunk said the Tilapia were a pest fish who threaten native species because of the unique way they breed.
“The way they breed is quite interesting – they lay their eggs and carry them around until they hatch in their mouths, so other fish and animals can’t eat them. That is why they breed so quickly.”
“As far as invasive species go, you couldn’t put a worse one in for displacing native fish.”
In the last couple of weeks the temperature of the water has dropped again.
So far only a few dead Tilapia have been spotted floating in the lake, but as the weather gets colder there will likely be many more.
Cr Strunk said people shouldn’t worry if they notice an increase in dead Tilapia fish at the lake over the coming months.
“The water quality at Forest Lake currently is very good, so there’s no issue with that,” he said.
Anyone with questions is invited to contact the Forest Lake Ward office on 3407 1211.