How Do Eels Reproduce?

Quck answer

Eels reproduce through a process called spawning, where the female eel releases eggs into the water and the male eel fertilizes them. After fertilization, the eggs hatch into larvae, which drift with ocean currents until they reach freshwater habitats. Once in freshwater, the larvae metamorphose into glass eels, which then grow and mature into adult eels. Adult eels migrate back to the ocean to spawn and continue the cycle. The exact details of eel reproduction are still not fully understood, and scientists continue to study this fascinating process.

Wild Animals

The question of how eels reproduce has been asked frequently online. Eels are a type of fish that can be seen in aquariums or seafood restaurants. Despite being studied for thousands of years, some aspects of their breeding lives remain a mystery. To learn more about eel reproduction, Caroline Durif, an ecologist at the Institute of Marine Research in StorebГё, Norway, was interviewed.

What is an Eel?

Eels belong to the order Anguilliformes, which contains all of the world’s “true” eels. There are over 800 species of true eels, including morays, conger eels, and spaghetti eels. True eels do not have pelvic fins and can be scaleless. While saltwater is the preferred habitat for most eels, there are 19 species of “freshwater eels” that spend much of their lives in freshwater. These eels spawn in the sea and grow in freshwater. The three best-known species of freshwater eels are the European eel, the American eel, and the Japanese eel.

Early Life Stages of an Eel

The life cycle of eels is complex and consists of five distinct stages. The first stage is the leptocephalus larva, which has a leaf-shaped body and is nearly transparent. The larvae are oceangoing animals, but eventually, they migrate to find a change in scenery, which is when they enter the second phase of their life cycle. In this phase, they metamorphose into glass eels, which are longer and skinnier than leptocephalus larvae.

These glass eels were caught on the French Atlantic coast in 2021 after traveling for about 2,796 miles (4,500 kilometers) from the Gulf of Mexico through the Atlantic on their one- to two-year migration. The next stage for most anguillid glass eels is to travel up rivers as they are attracted to freshwater. The third stage, called “yellow eels,” have body pigment and a yellowish complexion. They then become silver eels, which is like puberty, and have a silver belly and black dorsal area to adapt to predation. This transition can take 20 or 30 years, and once it ends, they head seaward and attain sexual maturity, the fifth and final stage in their life cycle. Scientists do not know much about the reproductive stage of anguillid eels because sexually mature eels have never been caught alive in the wild. Freshwater eels die shortly after mating, and their health declines after sexual maturity. The Sargasso Sea is a region in the Atlantic Ocean where both American and European eels come to reproduce, and they might use magnetic fields as a navigation tool. Freshwater eels in the Pacific Ocean have their spawning areas, with the Japanese eel breeding west of the Mariana Islands, and the European eel having the longest migration of about 4,971 miles (8,000 kilometers) to reach the Sargasso Sea from Norway. Eels release their eggs underwater, to be fertilized by clouds of expelled sperm, regardless of their habitat.

Durif suggests that our knowledge of conger eels in terms of reproduction is even more limited than that of anguillid eels. He speculates that there may be a spawning area for conger eels, possibly in the Mediterranean. It is hoped that further research will provide insights into their private lives.

Interestingly, some eels have a complex feeding process where food is sucked into their mouth and then broken down into smaller, digestible pieces through shaking or twisting. On the other hand, moray eels use a second set of jaws to assist with killing their prey, which is quite terrifying.

FAQ

1. What is the reproductive cycle of eels?

Eels have a unique life cycle that involves migrating vast distances to breed. They spawn once in their lives, in the Sargasso Sea, and then die. The young hatch and drift with ocean currents for several years before arriving at the continental shelf and migrating upstream to freshwater habitats.

2. How do eels find mates?

Male eels produce sperm and release it into the water, where female eels swim through it to fertilize their eggs. There is no physical interaction between males and females, and it is not yet known how eels find each other in the vastness of the ocean.

3. How do eels reproduce in captivity?

Reproducing eels in captivity is a difficult process because they require specific water conditions and stimuli to trigger reproduction. However, some research has shown success with hormonal injections and artificial reproduction techniques.

4. How long does it take for eels to reach sexual maturity?

Eels take a long time to reach sexual maturity, with some species taking up to 20 years to do so. This, combined with their unique life cycle, makes them difficult to study and breed in captivity.

5. Do male and female eels look different?

Male and female eels look very similar, making it difficult to tell them apart visually. However, scientists have found that males have larger heads and eyes than females.

6. How many eggs do female eels lay?

Female eels can lay millions of eggs at once, depending on their size and species. However, only a small percentage of these eggs will successfully hatch and survive to adulthood.

7. How are eel eggs fertilized?

Male eels release their sperm into the water, where it drifts until it reaches the eggs released by females. The sperm and egg combine to form a fertilized egg, which then develops into a larval eel.

8. Do eels mate for life?

Eels do not mate for life and have no pair bonding behavior. Once they have spawned, they will never reproduce again and will die soon after their migration.

9. Are eels endangered due to their unique reproductive cycle?

Eels are currently listed as endangered by the International Union for Conservation of Nature. Their unique life cycle, combined with overfishing, pollution, and habitat destruction, has led to a significant decline in their population. Efforts are being made to conserve and protect eel populations, but more research is needed to fully understand their reproductive cycle and behavior.