How Many Eggs Can an American Eel Lay in A Year?

Written by in Fishing
Image Credits: Wikimedia Commons

Ever wondered how many eggs an American Eel lay each year? I set out to find the facts and figures. Read my blog post about the full life of the american eel here.

American eels live an extreme example of a full circle life: they’re born in the Atlantic, live for five to twenty years in freshwater, and then venture back out to the ocean to breed and perish. During their entire lives, this is the only time American eels will spawn.

How Many Eggs Can an American Eel Lay in a Year? Female American eels can carry upwards of 20 to 30 million eggs. Eels only breed once in their life, migrating to the Sargasso Sea where they then spawn and presumably die.

Join the community
Get the latest contet, reviews and launches from Bob
Sign up for the email newsletter today

Reproduction and laying eggs of eels has long been a mystery. 

No one has ever witnessed American eels spawning, and no one knows what happens to the eels afterward. 

But, in recent years, researchers have been starting to put together a picture of what happens in the sea.

So, How Many Eggs Can an American Eel Lay in a Year?

Some estimates state that female eels release 4 million eggs once they return to the Sargasso Sea, while others put the number around 20 to 30 million fertilized eggs.

The older and longer the female, the more eggs she can carry. 

The largest and most fertile of females?reaching the higher egg estimates?typically are reported to come out of inland Canada.

A 2018 article in the journal Marine and Coastal Fisheries took a stab at estimating how many eggs American eels carried, also known as their fecundity, from four different studies.

These sampled female American eels were found to be carrying between 0.5 to 22 million eggs. 

Generally, short females early in their migratory route have fewer eggs.

Things that can lead to female eels carrying more eggs include:

  • The eel’s body length.
  • How far along in her migratory route she is.

Once eggs are laid, it’s hard to know what exactly happens next. 

Much of what happens to eels in the open ocean is still largely a mystery.

We know that the eggs hatch and the larvae find their way to freshwater, and it’s believed that, after their long journey, the adults pass away.

How do American Eels Reproduce?

When an American eel reaches reproductive maturity, their body undergoes dramatic physical changes to transform it from bottom dwellers in rivers to ocean fish. American eels will stop eating entirely and rely on fat reserves to make the long journey.

When ready to spawn, the physical changes eels undergo are:

  • Degeneration of their gut
  • Their eyes growing in size
  • More blood vessels in their swim bladders
  • An increase in fat reserves

Male American eels reach sexual maturity sooner in life, usually when around five to ten years old, and begin their migration to the Sargasso Sea. 

Female eels live for longer before reaching maturity, the largest going for over twenty years before beginning their migration.

American eels can travel thousands of kilometers in this migration to their breeding grounds. 

One eel was tracked by researchers all the way from Nova Scotia to the Sargasso Sea, traveling roughly 2,400 km in 45 days.

Once American eels reach the Sargasso Sea, however, the rest is still a mystery. 

No researcher has ever observed American eels spawning in the wild. 

It’s currently believed that, after spawning, American eels die.

Based off of where larvae are found on the eastern seaboard, researchers have built models to try and simulate how the larva make it to shore. 

Their models suggest that at least a little bit of swimming is involved, or else we wouldn’t see such a wide spread of larvae across so much of eastern North America.

Despite the lack of attention American eels may get, they live a life fit for a fable. 

They live their whole lives before their bodies begin to change for the migration to spawn. And after traveling thousands of kilometers to the same sea that they were born in, they breed and vanish.

American Eel

American eels (Anguilla rostrata) are a catadromous fish, meaning they spend most of their lives in freshwater before migrating to the sea to breed. Reproduction of American eels in the wild, however, has proven to be an elusive area.

It has long been believed that American eels spawn in the Sargasso Sea?a region of the North Atlantic Ocean bounded by the Gulf Stream, North Atlantic Current, North Atlantic Equatorial Current, and Canary Current.

The Sargasso Sea was proposed as the single spawning area of American eels as far back as 1904, but it took until 2015 for researchers to finally track an adult eel along its migratory route.

By tagging eels with pop-up satellite archival tags, or PSATs, researchers from the Université Laval in Québec and Dalhousie University in Nova Scotia tracked migrating American eels.

While it has now been confirmed that an adult American eel did travel to the Sargasso Sea, there still hasn’t been any observed egg laying in the wild. Whatever effect environmental changes may have on their spawning and reproduction is unclear.

Hatched larvae drift and swim to the continental shelf, where they then leave the ocean and transition to living in brackish water and freshwater. 

American eels land in most corners of the Atlantic coastline, where their adaptability helps it survive in so many diverse habitats.

American eels go through a cycle of transformations. In freshwater, American eels metamorphose through different life stages where they exhibit different physical characteristics.

The life stages of American eels:

  • Eggs
  • Leptocephali (larva)
  • Glass Eels
  • Elvers
  • Yellow eels
  • Silver eels

Males tend to mature and return to the Sargasso Sea within five to ten years, while females can live in freshwater and brackish water for twenty years before migrating to the sea. 

One mature female eel recorded in Nova Scotia lived to age 43. 

Eels kept in aquariums will typically live around ten years.

Interestingly, eels are sexually undifferentiated as larvae and glass eels. It isn’t until they’re already in freshwater that they begin to differentiate into males in females.

Often, eels that grow quickly as glass eels tend to become males while eels that grow slowly at the start of their lives develop as females.

The environment a glass eel experiences seems to largely influence the sex it’ll develop into. 

When in aquaculture, glass eels usually differentiate into males. It’s suspected that this is because of stress and cortisol levels.

Females tend to be the ones to venture further inland, swimming upstream, and can grow to five feet in length. Males usually stay in estuarine waters and can reach three feet.

American eels range as far north as Greenland and have been reported as far south as Venezuela. 

While their movements aren’t as well recorded outside of Canada and the U.S., American eels are believed to also currently range through eastern Mexico and the Caribbean.

Related Questions

Do all American eels eventually migrate back to the Sargasso Sea?

Some researchers categorize American eels as “facultative catadromous,” meaning that their migration pattern may not be as obligatory as once believed. But to the best of current knowledge, American eels do make the trip back to the sea when it’s time to spawn.

How do American eels know when it’s time to spawn?

When an American eel is ready to spawn, its body begins to physically change for the journey. Little is known, however, on what triggers those changes.

How many eggs actually get fertilized?

American eel eggs are fertilized externally (after being laid) and are believed to hatch within a week or two. But what happens during spawning in the Sargasso Sea is still largely a mystery.

Do you want to become a paid freelance writer for BonfireBob.com?
Apply now at [email protected]. Please include a sample of your writings and tell us why you are passioned about the outdoors!
Author Bio
Patrick Author BonfireBob

My name is , and I am the main Author and owner of BonfireBob.com

I live in a smaller town, very close to a bigger city and I love the Outdoors!

BonfireBob is my outlet, and my escape from the every day lives. I write about fishing, hiking, climbing, gear, camping and much more, enjoy!

My Favourite Content
Related posts
Fishing
Fishing can be a great way to introduce people of all ages to the great outdoors. With a range of styles, fishing is something that can be learned in a few minutes but takes a lifetime to master. One part of this mastery is knowing what kind of gear and a
Fishing
Fishing is one of the most sought after pastimes for all types of outdoor enthusiasts alike. There is no surprise that you might already be thinking about planning a fishing trip for yourself. The most important factor to consider before you go, though, i
Fishing
When it comes to taking any kind of fishing trip, it is true that there are several pieces of equipment involved for a successful journey. However, the most important aspect is how you store this equipment, namely your fishing rod, in order to avoid any p
Fishing
After thinking about the fishing trips that I would take with my family when I was younger, I remembered all of the frustration troubles that I had with stringing my rod the wrong way. No matter how many times I tried with different kinds of reels, I alwa
Fishing
Fishing is one of the most popular pastimes throughout the entire world. While many people enjoy this activity, most don’t know that properly casting your rod is the key to catching fish. When your baited line is properly cast, fish will be attracted to y
Fishing
Setting up for a fishing trip can be a long process, but one that can be easily executed if you have the knowledge that will make for a smoother trip. There are many variables that come with setting up for a fishing trip as a whole, but even more when it