How far would you be willing to wander for a date? Probably not as far as this aquatic animal.
Long and short-fin eels travel more than 3,000 kilometres from waterways across Victoria to the Coral Sea, and for the first time, researchers have been able to officially pinpoint where the eels breed.
Scientists hoped a better understanding of migratory patterns would help reverse the species' declining population.
The recent discovery came amid a research project by the Arthur Rylah Institute, in partnership with Gunditjmara traditional custodians.
Twenty transmitters were attached to freshwater eels in 2019 at the start of the project.
The tagged eels were tracked over the course of five months and were seen moving all the way from the south-west of Victoria to the Coral Sea near New Caledonia.
The eels can live for decades and grow as long as a metre and weight up to 3 kilograms.
Wayne Koster leads the research on native fish ecology and conservation and said there were not many migration patterns comparable to the eels' journey.
"These migrations are pretty epic … there are bird species that travel all the way from Siberia to places like Australia … but as far as fish go, these are pretty large-scale movements," Dr Koster said.
River flow vital to eels' journey
Researchers have been targeting the fish in Lake Condah, also known by its Gunditjmara name Tae Rak, Darlots Creek and the Hopkins river.
"What we wanted to understand was, what are the environmental cues for the eels to start their migration to breed? And then once they leave fresh water, what happens along the way?" Dr Koster said.
"So, some of the things we've found out is, increases in river flows at certain times of the year can be really important in terms of getting them to start their migrations.
"That has implications in terms of how we allocate the water for the environment."
Dr Koster said there was plenty of mystery surrounding the eels and more research was needed to better understand the native Australian species.
"We also don't have a great handle on the factors that are informing the recruitment of juveniles back into fresh water," Dr Koster said.
"So, after they have spent the first six to 12 months floating around in the ocean … when they come back into the freshwater, what are the factors that are driving those migrations?"
Importance food source for First Nations
The research is in collaboration with the region's traditional custodians, the Gunditjmara people.
Gunditjmara man and world heritage park ranger at Gunditj Mirring Traditional Owners Aboriginal Corporation, Tyson Lovett-Murray, said "it can't be overstated" how culturally significant the eels were to the south-west Victorian Indigenous community.
"Traditionally, for thousands of years it was a food source, and led to the Gunditjmara community engineering a really big landscape around short finned eels," Mr Lovett-Murray said.
"There are 350 recorded stone house sites on the cultural landscape, and they're all attached to huge swamps that were formed by the eruption of Budj Bim, formerly known at Mount Eccles."
Mr Lovett-Murray said it was vitally important for the community to have a better understanding of the impact of climate change on waterways and the species that inhabit the area.
"Our world view is always based around the collective, sustainability … its something our community has carried right through colonisation," he said.
"So when you get these government agencies that are doing really good biodiversity work, it's really important that we advocate to have our voice heard."
