School may be out across the ACT, but the end of the year also means a school of a different kind was in Canberra's waterways.
Lake Burley Griffin received thousands of new residents on Monday, as 22,000 Murray cod were released into the environment.
The mass fish release was a bid to help improve the lake's ecosystem and help eradicate pest species such as carp and redfin.
While the fish released into the waterways are only six-weeks-old and just five centimetres, they're expected to reach full size in four years and be native predators.
ACT government senior aquatic ecologist Lisa Evans said the scheme aimed at introducing native species more commonly found in other waterways into urban lakes.
"They're there to help balance the ecology of the lake because they do have problems with carp and redfin taking over," Dr Evans said.
"It also takes pressure of natural rivers and encourages people to go fishing in local areas near their homes."
Monday's mass release of cod into Lake Burley Griffin coincided with similar large-scale releases into other waterways in Canberra, including Yerrabi Pond and Upper Stranger Pond.
More than 39,000 fish were released in the ACT as part of the the government's fish stocking plan this year.
It's estimated more than 1 million fish have been stocked in ACT lakes and ponds since the program began in 2000.
More than $35,000 was spent in 2019 on restocking fish in the waterways.
"There is the potential if you introduce a large predator like Murray cod early on in the lake before pests can become established, they can feed on the juvenile pest fish and can keep carp numbers lower," Dr Evans said.
Previous culls of carp in the ACT netted more than five tonnes of the species.
It's hoped the release of the Murray cod into Canberra's most famous lake will allow for a large population of the species to flourish.
Dr Evans said although Murray cod weren't normally found in lakes near cities, she hoped they would be able proposer in Lake Burley Griffin.
"Urban lakes don't normally provide habitats for Murray cod spawning, they prefer running water and structural habits like rocks and logs," she said.
"Unfortunately, they don't tend to breed in the lakes, which is why we need to stock them every few years."
It's hoped the release of the fish would relieve pressure off other waterway areas such as rivers and streams and provide more places for fishing in the ACT.
"We'd love to see ethical recreational fishing take place, so people are aware of the rules and they're not taking too many fish," Dr Evans said.
