Short-finned eels swim more than 3000kms against the current to reach the Coral Sea. Photo: Arthur Rylah Institute
By Catherine Watson
SHORT-tailed shearwaters are not the only local animals setting off on an epic journey. Short-finned eels are also embarking on a long and arduous trek to the seas north of Australia.
While most of the shearwaters will make it back to Phillip Island next spring, the eels are making their final journey.
Short-finned eels are common, though rarely noticed, in estuarine rivers and creeks across mainland Bass Coast. They usually begin their migration unnoticed in mid-to-late autumn, but when estuaries are closed you can sometimes see them gathering at river mouths, waiting for a high tide to carry them across the bar.
SHORT-tailed shearwaters are not the only local animals setting off on an epic journey. Short-finned eels are also embarking on a long and arduous trek to the seas north of Australia.
While most of the shearwaters will make it back to Phillip Island next spring, the eels are making their final journey.
Short-finned eels are common, though rarely noticed, in estuarine rivers and creeks across mainland Bass Coast. They usually begin their migration unnoticed in mid-to-late autumn, but when estuaries are closed you can sometimes see them gathering at river mouths, waiting for a high tide to carry them across the bar.
A couple of weeks ago, local young citizen scientist Cormac Skinner captured the start of that hazardous journey in a video filmed at the Mouth of the Powlett.
Complete with Cormac’s engaging commentary, it shows the eels repeatedly trying to cross the bar while Pacific gulls wait nearby for a king-sized snack.
Callum Edwards, coastal waterways officer for the West Gippsland Catchment Management Authority, was lucky enough to witness a similar congregation of eels at the Mouth of the Powlett a few years ago and says it was an unforgettable sight.
“They can sense when there’s a storm coming and they come downstream to wait for the high tide,” he says. “They really have to fight against the current to get out.”
The annual migration is part of a remarkable journey to the Coral Sea, south-east of Papua New Guinea, the sole spawning site for Australian and New Zealand freshwater eels.
The eels are long-lived but, once they reach maturity – between eight and 12 years for males and 10 to 20 years for females – their days are numbered.
According to the Victorian Fisheries Authority, the eels go through dramatic changes In preparation for the spawning migration. After a period of voracious feeding and rapid growth, their eyes enlarge, their skin turns silvery and their gonads begin to develop. At the same time, their digestive system shuts down and starts to degenerate.
Now known as “silver” eels, they migrate to sea in late summer and autumn, moving quickly into deeper water and swimming north in total darkness against the current to reach the Coral Sea.
Callum Edwards, coastal waterways officer for the West Gippsland Catchment Management Authority, was lucky enough to witness a similar congregation of eels at the Mouth of the Powlett a few years ago and says it was an unforgettable sight.
“They can sense when there’s a storm coming and they come downstream to wait for the high tide,” he says. “They really have to fight against the current to get out.”
The annual migration is part of a remarkable journey to the Coral Sea, south-east of Papua New Guinea, the sole spawning site for Australian and New Zealand freshwater eels.
The eels are long-lived but, once they reach maturity – between eight and 12 years for males and 10 to 20 years for females – their days are numbered.
According to the Victorian Fisheries Authority, the eels go through dramatic changes In preparation for the spawning migration. After a period of voracious feeding and rapid growth, their eyes enlarge, their skin turns silvery and their gonads begin to develop. At the same time, their digestive system shuts down and starts to degenerate.
Now known as “silver” eels, they migrate to sea in late summer and autumn, moving quickly into deeper water and swimming north in total darkness against the current to reach the Coral Sea.
“By the time they arrive, they have basically used up all their energy resources and are little more than a skeleton with gonads. They spawn and die and their young commence the cycle over again.” |
The return journey of their offspring is equally perilous, though their fate is less certain. In late winter, tiny transparent larvae depend on erratic eddy currents to carry them south to Bass Strait. Some make it; most do not.
“In years when these currents are strong, there is a massive arrival of glass eels along the Victorian coast, but in some years the currents are weak and very few glass eels arrive.”
Around the Victorian coast, the young eels detect freshwater flows from rivers and creeks and head for estuaries. In dry years, when river flows are low, many are unable to cross the bar and die.
In wetter years they move quickly into estuaries and migrate upstream to rivers, creeks, lakes and swamps, where they spend their long adolescence – before they too begin their second and final great migration back to the Coral Sea, where their lives began.
“In years when these currents are strong, there is a massive arrival of glass eels along the Victorian coast, but in some years the currents are weak and very few glass eels arrive.”
Around the Victorian coast, the young eels detect freshwater flows from rivers and creeks and head for estuaries. In dry years, when river flows are low, many are unable to cross the bar and die.
In wetter years they move quickly into estuaries and migrate upstream to rivers, creeks, lakes and swamps, where they spend their long adolescence – before they too begin their second and final great migration back to the Coral Sea, where their lives began.
Illustration: Edgar R. Waite, Illustrated Catalogue of the Fishes of South Australia,
G. Hassell & Son, Adelaide, 1921.
G. Hassell & Son, Adelaide, 1921.