How Do Eels Reproduce? Know The Details Right Here!

The lifecycle of European Eels(even their American counterparts), a staple of the continent’s cuisine and culture, has always been shrouded in mystery. Until recently, nobody knew – how do eels reproduce. Questions about the same have resurfaced recently when the International Council For The Exploration Of The Sea (ICES), released its 2024 Annual Report. It recommended a fishing ban to protect the species – “there should be zero catches in all habitats.” This news has taken netizens back to recovering an old TikTok video titled – We Don’t Know Where Eels Come From by ColeTheScienceDude. That video spoke of the – lack of information on the reproductive and lifecycle of eels. However, things are getting a bit clearer now! 

Though multiple factors are still under study, we have gained a basic understanding of their reproductive cycle, mating process in the wild, and how they survive this consistent migration. Let us share the same with you – 

Where and how do eels reproduce? 

How Do Eels Reproduce in sea
Image Credit: Animals|HowStuffWorks

Multiple pieces of research show that – the Sargasso Sea is the spawning ground for eels. Supposedly, eels move from freshwater and migrate to the seawater to reproduce. From what studies show, European and American eels from various parts of the world (Baltic, western Mediterranean, Celtic, Europe, North America, and Caribbean) arrive at the Sargasso Sea. 

These eels are the ideal example of metamorphosis since, in the course of their lives, they categorically transform into four distinct beings. The journey kickstarts from a gossamer larva with big eyes, followed by a ‘glass eel’ formation (elver). This leads to the formation of the yellow-brown eel and finally ends with the last stage of being the silver eel. 

  • Initially, it is the European eels that undertake the grueling journey to the Sargasso Sea. The reproduction process is through external fertilization and the mature eels die. 
  • The larva born, floats in the open sea towards Europe. It is the North Atlantic Drift that supports this journey. 
  • Once it reaches the destination, then the yellow-brow eel (that is its current colour) hibernates in a muddy area. 
  • After that, they turn into the silver slithery eels – as we know them – and carry forth the reproduction process by taking forth the arduous journey. In this last metamorphic stage, the eel will travel miles, specifically on its fat reserves, and its reproductive organs will develop for the first time. After this, the whole process continues as it is.
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This is the only relevant information found on their reproduction system. No instance of eel eggs or mature eels have been found in the Sargasso Sea.  

Why does the Sargasso Sea play a crucial role? 

sargasso sea
Image Credit: Live Science

For those who are curious about this focal point constantly and consistently coming to the forefront, for the record, the Sargasso Sea is considered to be a sea within a sea. It is also bound by seaweed on all sides, with high currents flowing through it. These features consistently make this ‘the ultimate’ breeding ground for eels (American and European varieties). 

Why is finding data on eels mating in the wild so complex? 

You have seen for yourself how researchers uncovered (and are in the process of uncovering further data on) how do eels reproduce in the wild (with the Sargasso Sea as the meeting point). But hereon, the problem again is that tracking the migration of Anguillid eels becomes extremely difficult. Also, recent revelations show that the breeding takes place below 1000 feet, which is further influenced by a host of factors. 

Given the lack of available data, the stream of challenges, and the escalating costs associated with the discoveries, finding data on the eels (in the wild) becomes exceptionally complex. The only aspect that we have been able to get complete clarity on is that Anguillid eels’ life cycle includes migrations between continental waters (areas where they grow and feed) followed by their breeding process that occurs in the open ocean. 

How do eels survive the migration process? 

how eels reproduce in the wild
Image Credit: IFL Science

Apart from knowing how do eels reproduce most people also wish to know – how they survive this migration process (from freshwater to saltwater). We will update you on the same – 

It is believed that the European eel migration is one of the most strenuous migrations ever documented in marine history. This 3000-mile-long journey takes from 80-170 days, and eels seem to rely on the lunar cycle for the same. 

Theories also state that – during this journey, the eels do not consume anything and rely on the blood vessels around their bladder. This results in their eyes doubling and increased sensitivity (especially in the dark). Also, given that they are travelling from freshwater to saltwater, their kidneys adapt to hold ‘increased salt content’, thereby making this transition easier.  

What questions remain in mystery? 

American-Eels in sargasso sea
Image Credit: MeatEater

Though we are gradually becoming more aware of where and how eels reproduce, some questions still need to be answered. Let us take a look at those – 

  1. How do eels navigate through thousands of kilometres to reach their spawning ground at the Sargasso Sea? 
  2. How do the eels timing their meeting? 
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From the data that certain fish ecologists have uncovered, we may state that – 

Eels tend to uncover the earth’s magnetic field. Hence, they use that to return to the old stream where they initially hatched their eggs. Apart from that, they might also use their olfactory responses, pick up cues from ocean temperature, and even track ocean currents (the North Atlantic gyre creates the ideal temperature for breeding). However, the theories stated above are mostly conjectures with no solid foundation to support them. Research on the same is underway. 

Closing thoughts 

One of the most complex of the aquatic species, how do eels reproduce has remained a mysterious query for one and all! Though, in recent times, we have been able to decode its basic reproductive cycle, unanswered questions remain. The eels’ mysterious lifecycle has, for a long time, resisted fisheries science. Now, with spawning stock biomass, research seems to be looking up! 

For those of you who enjoyed this post, do leave your comments below. Keep an eye on this website for more information. 

Frequently Asked Questions 

1. Can eels be bred in captivity? 

You must understand that the eels reproduce through external fertilization and follow a whole transition and spawning process over 170 days. Though some stages of eel breeding in captivity have been achieved, there has been no massive progress on the whole. 

2. What is an eel’s lifespan?

The lifespan of an eel depends on its species. While the European eels are said to have lived up to 80 years, their American counterpart seems to live only for a maximum of 20 years. Having said that, they can even swim for hours together with their heads cut off! 

3. Do eels have a reproductive system? 

This query of whether eels have a reproductive system and how do eels reproduce has engaged one and all – from Aristotle to today’s ecologists. For the record, they do have a reproductive system(within their abdominal cavity), but it only matures at a much later stage in their lives. 

4. How are electric eels different from real ones? 

For starters, electric eels have no similarity with eels. Categorized under the order of Gymnotiformes, they share similarities with catfishes and carp. In fact, quite unlike the true eels, they reproduce during the dry season, wherein males create a nest out of their saliva for the females to deposit their eggs.