Anguilliformes or eels are fascinating creatures with long bodies, which make them resemble snakes. Over 800 species of it exist, with some found in freshwater and the sea. Eels exist around the world, and unsurprisingly people often eat them as food. For example, they are delicacies in some parts of Japan. Now despite their prevalence, there are still so many things we do not know about eels. In fact, we do not even know exactly how do eels reproduce. That’s right: eel reproduction is quite mysterious! This is despite centuries of studies and observations. How is this possible? How can we not know about the reproductive habits of one of the world’s most common kinds of fish? That is what this article will explain, and more.

How Eels Reproduce in the Wild is Mysterious

How is eel reproduction mysterious? For one thing, scientists have never observed eel spawning in the wild. Their exact spawning grounds remained mysterious for centuries. Only recently have the spawning grounds for many eel species been located. Even then, exactly how they move between their spawning and living grounds is unclear. Even their exact methods of reproduction remain largely unknown, as we will see later.

While many aspects of eel reproduction remain mysterious, other aspects have become more clear over time.

What is the Life Cycle of an Eel?

Before we dive into eel reproduction, it may be first worth describing an eel’s life cycle.

Eels, like most kinds of fish, begin their lives as eggs. These eggs hatch into larvae called leptocephali (singular leptocephalus). These are tiny creatures, less than 0.2 in (5 mm) in size. They often engage in vertical migration. This means they alternate between living at the top and bottom of bodies of water. Eels can remain in this stage for anywhere between six months to up to two years.

After this, the young eels turn into glass eels. These are larger yet small transparent juveniles (hence the name “glass” eel). They migrate from spawning grounds to their usual living grounds. Such migrations can take thousands of miles. Over time they grow in size, eventually becoming elvers. This is a stage where the eels enter freshwater bodies of water. Eventually, eels live out their lives in these bodies, then eventually return to their spawning grounds. There, they spawn and die.

How is eel reproduction mysterious when we know its life cycle? For one thing, eel spawning in the wild has never been observed. Even their exact spawning grounds were obscure for centuries. Only recently have the spawning grounds for many eel species been located. Even their exact methods of reproduction remain unclear, as we will see later.

Where do Eels Reproduce?

As mentioned earlier, eel spawning grounds are different from their actual living grounds. This is especially the case for freshwater species, but even for marine species.

The Sargasso Sea in the Atlantic Ocean is the breeding ground for European and American eels. It takes its name from the sargassum seaweed that is abundant in the area. The Sargasso Sea is unique among all seas as it has no land borders of any kind. Instead, it gets its boundaries from sea currents in the Atlantic Ocean.

The Sargasso Sea is home to many species of marine life and is economically and ecologically important. In addition to being the spawning ground for eels, it is also home to crustaceans and other forms of fish.

How did people discover that this area was where eels bred? It took years of expeditions and observations. Scientists scouted the oceans, looking for eels in their juvenile states. As they went through the seas, they noticed that juveniles got smaller and smaller. Eventually, they noticed that juveniles in the Sargasso Sea were the smallest they could find.