How Do Eels Mate? Their Unique Way of Reproduction Explained

Eels are one of the most fascinating creatures on the planet; they have become the subject of countless myths and legends. For the longest time, eel reproduction has been a mystery; not until recently when researchers began to understand the process.

To help understand the process of eel reproduction, it is important to know the five extremely complex stages of the eel's life cycle.

Life Cycle of an Eel

Like most kinds of fish, eels begin their lives as eggs. These eggs hatch into tiny larvae known as leptocephali, which measure less than 0.2 in (5 mm) in size. This is the stage in the eel life cycle that is often engaged in vertical migration, which means that they alternate between living at the top and bottom of bodies of water. Eel larvae live in the ocean and typically remain in this stage between six months and up to two years.

In the next stage, the young eels turn into larger transparent juveniles called glass eels. At this point, they migrate from spawning grounds to their usual living grounds, which can take thousands of miles. The glass eels find their way into areas where saltwater and freshwater ecosystems mix, like protected estuaries.

Over time, the glass eels grow in size and become elvers, the pre-adult stage, which occurs once the eels are around two to three years old. This is the point where the eels enter freshwater, live out their lives, and return to their spawning grounds.

How Do Eels Mate?

Researchers are unsure when eels develop their sexual organs because they are not found in juvenile eels. However, they have recorded gonads in their late juvenile stage upon reaching 11 inches (26 cm) in length.

Experts believe that environmental factors such as temperature and salinity levels determine when eels reach sexual maturity. It is also possible that low eel populations result in the production of more females.

When eels reach adulthood, it is the time when their life ends. Thus, eels are determined to continue their life cycle once they hit this stage. They travel thousands of miles to their spawning site where they spend their remaining days.

Spawning is the last thing eels do before they die, and spawning habits differ between wild populations due to environmental factors like current flow rates, temperature changes, and food availability. Generally speaking, most adult wild eels migrate towards shallower waters during spring when water temperature rises. At this point, hundreds to thousands of eels can mate simultaneously, forming a giant, blackish-brown squirming cloud. Doing so increases the chances of fertilizing the egg successfully.

Researchers believe that eels mate through external fertilization. When the eels arrive in the spawning ground, the females lay their eggs in the surrounding water. At the same time, the males also release their sperm in the water column. When the eggs come into contact with the sperm, they become fertilized. It is thought that a single female eel can produce between 2-10 million eggs.

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