The mention of eels often sees people cringing in revulsion.  The thought of a slimy snake-like animal lurking beneath your feet is enough to turn many people off swimming at their local waterway.  However, our perceptions of fresh water eels as grotesque monsters slithering around at our feet waiting for the opportune moment to strike couldn’t be further from the truth.  In reality the life of an eel is an adventure of extraordinary hardship and perseverance, involving migrations of epic proportions requiring highly developed senses and unwavering endurance, resulting in certain death at the depths of a cold, dark ocean having travelled thousands of kilometres throughout their life time.

The gruelling life cycle of an eel beings way out in the South Pacific Ocean somewhere in the Coral Sea, in a location that is still elusive to scientists, even in the year 2011!!  As tiny transparent larvae, these little animals travel southwards along currents that lie parallel to the east coast of Australia.  Along their journey they feed on tiny planktonic animals who are also hitching a ride on the currents.  During this time the larvae metamorphose into small, transparent eel-shaped animals called ‘glass eels’.

Once the glass eels reach the continental shelf of Australia, they are able to detect the presence of estuaries signified by changes in salinity using their acute sense of smell.  However their detection of these estuaries is largely determined by the rate of flow; in years of low flow the glass eels are less able to smell the changes in salinity resulting in lower numbers, sometimes none reaching those waterways.  Their ability to reach specifically Victorian waters lies in the formation of erratic currents which split off from the east Australian current.  The degeneration of these currents before reaching the Murray River explains the absence of eels in the Murray River.  The fluctuating strength of these currents also determines the number of eels who make it into freshwater rivers and streams.  Large numbers of glass eels make their way into rivers when the currents are strong.  Likewise, when the currents are weak the number of eels is reduced.

Some of these glass eels may live in freshwater estuaries for some time, gradually taking on the dark appearance we normally associate with eels, and moving into the stage of ‘elvers’.  However, others seeking yet another challenge undertake a further migration upstream called an eel fare.  In this migration elvers and glass eels make their way inland to rivers, creeks and swamps.

The eels may remain in these habitats for up to 20 years growing and feeding on small fish and invertebrates using their rough plate-like teeth to grind up prey before preparing to make the long trek all the way back to the Coral Sea.  In preparation for their long trek, their eyes become bigger, their digestive system starts to degenerate and they start to develop their gonads.  They also take on a silvery appearance and at this stage are known as ‘silver’ eels.  They move into deep, dark water and swim against the east Australian current in total darkness until they reach the Coral Sea.  Having used up all of their energy reserves and looking more like a skeleton with gonads than an eel, they reach their destination only to breed and die, with their offspring beginning the lifecycle all over again.

Internationally, there is a huge commercial demand for eels and for an animal with such a slow growth rate, lengthy life cycle, and erratic environmental conditions which affect their ability to migrate, there is a strong potential for this resource to be overfished.  Thankfully this has not occurred because this resource is tightly controlled.  Additionally, 13,500km of rivers and streams in southern Victoria make up the habitat for fresh water eels.  Commercial eel fishing is allowed in less than three per cent of this, representing a small proportion of habitat, and therefore aiding the security of this resource.

So, the next time you spot an eel in your local waterway, instead of screaming in terror and running for the hills, spare a thought for the hardship of eels and marvel at the fascinating features that enable them to survive.