A gigantic specimen of a new species of jellyfish has washed up on a beach in Tasmania, shocking the local family who found it and exciting scientists.

Stretching 1.5m wide, the unnamed species of lion’s mane jellyfish was found on a beach at Howden south of Hobart by the Lim family last month.

Lisa-ann Gershwin, research scientist with CSIRO’s wealth from oceans flagship, told Guardian Australia it was among the biggest she’s ever seen in her career studying jellyfish.

“There is a bigger species in the Arctic, and it gets about 3m across the body, so there are biggers species out there, but not in Australia,” she said.

The species itself is one of three new species of lion’s mane in Tasmania and Gershwin is now working to properly name and classify them.

“It’s not new because it’s large,” she said of this latest creature.

“It’s new because its structural features are unlike other species, it just so happens that this one is huge … it’s the size of a Smart car.”

The discovery comes amid a recent increase in jellyfish in Tasmanian waters and around the world, but scientists don’t know what’s behind it – although they have suspicions.

“We’re actually seeing a lot of jellyfish blooming this year. It’s been a big year for gelatinous creatures of all sorts,” said Gershwin.

“It is pretty warm this year. A lot of the sorts of things that are happening around the world – not just climate change but also ocean acidification, eutrophication, introduced species, pollution, overfishing – they’re all impacting the whole world and we’re not immune here in Australia. It’s not like we’re on a different planet.

“The bigger take home part of this is … what effect all of those mouths are having on the ecosystem and in turn what effect that has on our way of life,” she said.

“Southern Australia is known for some of the best fisheries on the planet but what’s happening when those fish we’re relying on are competing for food with the jellyfish?”

Aside from the scientific curiosity, Gershwin said it was great the discovery was made by 12-year-old Xavier Lim, who she described as “chuffed” at the find.

"We were at the beach looking for shells and dad was like 'Whoa! Look at that' … I kind of touched it ... it was pretty cool," Lim told ABC.

Gershwin and her colleagues are looking into setting up long-term research projects to investigate the sudden proliferation of jellyfish.