If you've caught a waft of something fishy down by Lake Burley Griffin you are on to something.
Lake maintenance staff contracted by the National Capital Authority have been inspecting the area and disposing of dead fish daily.
An NCA spokesperson said "dead fish will smell" but the 200 dead carp collected by the contractor in the past two to three weeks was similar to past seasons.
Hot weather doesn't help with the odour, however the NCA explained rising water temperatures may be causing the fish to expire.
"It is difficult to establish how the fish may have died, but typically at this time each year, as the temperature of the water in the lake increases, carp are known to die from exhaustion during spawning," an NCA spokeswoman said.
Testing of algae and bacteria levels in the waterway is ongoing.
An increase in Enterococci bacteria levels caused the closure of the central basin, Yarralumla Beach, Weston Park East and Weston Park West to primary contact.
"An increase in water temperatures is known to support increasing bacteria levels and the average water temperature at the sample sites rose by an average of 4.5°C in one week, which is considered a reasonably quick increase," the NCA spokeswoman said.
Repeat samples were taken on Wednesday 30 November 2016 and the Central Basin, Yarralumla Beach and Weston Park West were re-opened.
Fisheries Research and Development Corporation ecologist Matt Barwick has an extensive knowledge of carp.
Nicknamed 'The Carpinator' by Deputy Prime Minister Barnaby Joyce, Mr Barwick was given the $15 million responsibility to look into the cost and benefit of using carp herpes in his role as national coordinator of the National Carp Control Plan.
He said the volume of dead fish collected from Lake Burley Griffin in the short time frame was worth looking into.
"I would be very surprised by what you are seeing there, numbers of around 200 dead carp, is a result of carp exhausting themselves during spawning behaviour" he said.
"I don't think those temperature changes would result in increased stress to the animals through reduced dissolved oxygen levels."
University of Canberra chair of water science Professor Ross Thompson said while the fish deaths were an "oddity" for Lake Burley Griffin so was the spike in lake temperature caused by a recent string of 30C plus days.
"Carp can certainly cope with slow rates of warming and very warm temperatures but when it suddenly jumps up as it has, for fish that are already stressed, and spawning is really stressful for carp, it can be enough to push them over the edge," he said.
"They are already in the shallows with a whole lot of other carp breeding so they are physiologically stressed and they end up in a situation where they can't get enough oxygen."
He said heatwave events were predicted to be more severe and frequent so clean up and management strategies needed to be fine-tuned to future proof the ACT against public health or water quality issues caused by a more intense carp mortality event.
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