People Are Just Learning What A Baby Eel Is Called

Eels are perhaps one of the most mysterious of the well-known fish; they might even be mistaken for the Loch Ness Monster. They have a complex catadromous life cycle, spending time in fresh and saltwater. But what is a baby eel called?

The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

Lifecycle of an American eel

A young American eel (Anguilla rostrata) starts life in the Sargasso Sea and is usually spawned in the late winter. The first or larval stage is known as a leptocephalus, and is said to be shaped similarly to a willow leaf. 

After drifting for several months, the leptocephalus stage transforms into what is known as a glass eel. As these glass eels leave the ocean and make their way up into rivers and streams they become known as elvers. 

Elvers can stay for many years in this freshwater environment, but eventually make their way back out into the sea to spawn and die.

Lifecycle of a European eel

The lifecycle of the European eel (Anguilla anguilla) is pretty similar to their American cousins'; they also hatch in the Sargasso Sea and the Sargasso Sea only. This patch of warm water is located in the North Atlantic between the West Indies and the Azores, but European eels eventually end up in places like Britain on the Somerset Levels. 

The tiny willow leaf-like eel larvae were once thought to be a different species entirely. There is much we still don’t know about what triggers a juvenile elver to turn into a mature adult, and what triggers the adults to head back out to sea to spawn. 

Yellow eels and silver eels

The names “yellow eel” and “silver eel” are also used for juvenile eels. 

Yellow eels are the longest stage of an eel's life, when it has moved from the sea to the freshwater rivers, and can be 7-20 years depending on conditions. 

Only when the subadult has reached an appropriate size and level of fat stores does it transform into a silver eel, the final stage. During this stage a litany of physical changes occur, whereby the eyes grow up to 10 times bigger, pectoral fins widen, and muscle mass increases. Then the silver eels head back out to the sea and the cycle begins again.