Big predatory fish may hold an important key to controlling Australia's algal bloom problems, according to CSIRO research currently under way on Queensland dams.

Blooms of toxic algae waterways and dams can prove disastrous by poisoning the water and killing livestock and wildlife ­ but the factors which combine to cause blooms to occur are complex.

CSIRO scientists Dr Vladimir Matveev and Dr Gary Jones consider that algal blooms may be partly due to imbalances in the aquatic food chain ­ too many algal cells and too few other water creatures dining on them to keep them under control.

In an intriguing twist, they suggest that one way to prevent the blooms may be to selectively stock waterways with large predatory fish. Dr Jones says the experiment is the first of its kind in Australia and preliminary results of their four year program indicate they just might be on the right track.

Imbalances between the different life forms in the aquatic food chain can arise from human activities such as overstocking of inappropriate fish species, changes in drainage and water use patterns, or loss of water plants from spraying or harvesting.

"Algae are at the base of the aquatic food chain, feeding zooplankton which are tiny animals like water fleas. These zooplankton in turn are eaten by small fish which are then preyed upon by larger fish such as barramundi and perch," Dr Jones says.

"If there are too many small fish in the dam, there will not be enough zooplankton left to keep the algae in check.

"One way to restore the natural balance is to introduce larger fish to keep the small fish numbers down ­ so allowing the algae-eating zooplankton to thrive."

The first stage of their research - an extensive two year base line monitoring program at Maroon Lake and Moogerah Lake, near Boonah, will determine the current food chain balances in the dams.

Dr Jones says preliminary monitoring shows there are indeed large numbers of firetail gudgeon, which prey on zooplankton, in these dams ­ and not many large fish.

The second stage will investigate how the food chain balance can be modified to encourage the algae-eating zooplankton, by selectively stocking the dams with large predatory fish to reduce the number of smaller fish.

The project is being undertaken with assistance from the Queensland Department of Natural Resources (DNR), the Queensland Department of Primary Industries (DPI) and the National Eutropication Management Program.

Dr Jones hopes that the local angling community will assist researchers with the final fish stocking and monitoring stages.

"The outcome of the research will be low cost management methods that prevent rather than control algal blooms by restoring the natural balance in waterways," Dr Jones says.

More information:
Dr Gary Jones, CSIRO Land & Water 07 3896 9516
Margaret Bryant, CSIRO Land & Water 08 9387 0215