Do Clownfish Mate For Life? How Finding Nemo Should Have Ended?

Mar 12, 2022

Do Clownfish Mate For Life

As primitive as we think they are, clownfish have one of the most interesting social systems in the animal kingdom. Changing sex, banishing competition, and maintaining a size-based hierarchy are just a few of the many exciting phenomena clownfish perform. 

We know they make doting parents as Finding Nemo depicted, but do clownfish also mate for life? And what happens when a mate dies? 

This is going to be a compelling read. Buckle up. 

Do Clownfish Mate For Life? 

Yes, clownfish mate for life. The biggest fish in the group is always the female. The second biggest will be the breeding male. And the pair mate for life. The rest of the group members consist of sexually immature males who have no role to play in the reproduction or continuity of the lineage. 

Research has shown that there’s at least a difference of 10 mm between the size of the fish as the pecking order descends. 

What Happens When A Clownfish Mate Dies?

If the beta male dies, the female will choose the next biggest male from the pecking order to be her mating partner. If the alpha female dies, the beta male will change sex and turn into a dominant female, whereas the now biggest male from the pecking order will be promoted to the position of a beta male. 

The new pair now mate for life and ensure the continuity of their lineage by producing hundreds of little clownfish until one of them gets eaten eventually. 

Depending on whether the male or female bites the dust, the vacant position(s) are filled once again, and the breeding cycle continues. 

Yes, you read that right. Clownfish can change their sex and turn into a female. This is because they are sequential hermaphrodites – born as males and can become females as they mature. 

But despite the capability, not everyone has that privilege. 

So, if Finding Nemo was actually based on scientific grounds, the ending would have been somewhat different. The climax that the movie showed is a far cry from what would happen in nature. 

Want to find out? Keep reading! 

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How Would Finding Nemo End If It Was Based On Clownfish’s Real Behavior?

In the movie, Nemo’s mother, Coral, gets eaten by a barracuda. So, when Coral leaves the mortal coil, Nemo’s father, Marlin, becomes an overprotective dad who moves heaven and earth to search for his young son. 

But had the film been based on clownfish’s actual behavior, the ending would have been drastically different. So yes, what you’re thinking is correct. 

Marlin should have turned into a female since he, as a breeding male, is the largest fish in the bunch. And since Nemo is the only clownfish around, he would have turned into the breeding male. 

Nemo (now a breeding male) would then mate with Marlin, his dad (now a female), and produce hundreds of young offspring! 

How Anemones Shaped Social Structure And Reproduction In Clownfish? 

At least two theories explain how clownfish’s symbiotic relationship with anemones has shaped their social structure and reproduction. Let’s see what they are. 

Clownfish and anemones have an endearing interspecies friendship. The fish uses its toxic host to hide from potential predators. In return, the fish offers food to the anemone and keeps it clean. 

First theory

The presence of predators like barracudas nearby means clownfish rarely leaves its host. Unfortunately, that also means it would be tough for a new female to come into the group should the alpha female die. 

Therefore, a clownfish’s ability to change sex ensures that the fish doesn’t have to stray from safety into unsafe waters to find a mate. 

Second Theory 

In the wild, an anemone hosts around 4-6 clownfish. The female is always the largest fish, the breeding male is the second-largest, and the rest are sexually immature males. 

So, it has been theorized that the limited space the anemones provide encouraged clownfish to create a breeding strategy that limits spawning opportunities to just 1 breeding pair. 

It’s also been speculated that the breeding pair stunts the growth of non-breeding males using tactics like depriving them of food. These strategies ensure that non-breeding juveniles don’t grow too big to threaten their reign.

Size does matter when you’re a clownfish. And it’s not always a good thing. If a non-breeding male is growing big and fast, the breeding pair can even resort to evicting or killing it.

Can Female Clownfish Change Partners?

Very little has been studied about a clownfish’s reproductive cycle and tendencies. Therefore, we don’t really know the answer. We don’t know the repercussions if a new dominant male is added into a tank that already houses an alpha female and a beta male. 

However, as it turns out, most hobbyists believe the female would abandon her current partner if the new male is bigger, stronger, and more aggressive. 

And that’s on evolution. Females are hardwired to identify and spawn with the best possible candidate in the tank. 

But note that there’s no scientific evidence to back up this claim. 

Clownfish Reproduction | Everything You Need To Know About It

Breeding clownfish is, of course, easier said than done. But it doesn’t require herculean effort. If you understand the details of the reproduction process, the idea of raising hundreds of young clownfish and selling them at an attractive price isn’t far-fetched. 

Below, I will break down information into small readable segments so you can navigate through them quickly. 

Choosing Your Clownfish Pair 

When choosing your clownfish pair, you basically have 4 options at your disposal. And all 4 of them come with unique sets of advantages and disadvantages. 

The first option is to buy a juvenile pair and wait (and pray) that they pair up. This is naturally the most cost-effective method. But there’s no guarantee that the duo will pair up. 

On top of that, females take as long as 2 years to sexually mature. So, if you can bide time, you can choose this route. 

The second option is to purchase a small male and a big female and once again hope that they will pair up. Apparently, you can even buy ‘proven’ fish with previous breeding experience. 

But note that there’s no certainty that the alpha female will agree to pair with the male you set up for her. 

The third option is to buy a bonded pair. Naturally, this option is more expensive than those mentioned above two. But the plus point here is that the couple may start breeding as soon as their requirements are met. 

If you have trust issues like me, you’d have problems telling if a pair is really bonded or not by watching 20-second footage or buying someone’s word for it. 

The fourth option is the most expensive, but it has the highest success rate. You can buy a breeding pair. If you go this route, you can be assured that the fish have bred previously and will breed readily once again. 

Anyway, no matter what route you go, just make sure to add the male fish first. If you fail to do so, the female may torture the male to the point he kicks the bucket. 

Setting Up Breeding Tank And Conditioning Pair To Breed

If you are really keen on breeding clownfish, you must set up a breeding tank. But if you’d like to leave things to chance, you can wait for them to breed in the community tank. 

I’ll assume that you’ll pick the first route for this article. 

A 20-gallon tank would be more than enough to accommodate a breeding pair. That’s because once they choose a breeding spot, they will hardly swim away from it. 

As it goes without saying, equip the tank with a reliable heater, filter, and air pump. The temperature should be set somewhere around 83 degrees F. 

 Also, fully cycle the tank and make sure the parameters are perfect. 

Lastly, add a couple of tiles and clay pots to serve as breeding spots for the fish. 

To encourage the fish to breed, feed protein-rich food multiple times a day, and perform water changes routinely. 

Courtship And Mating Rituals 

Although clownfish reproduce asexually, they perform courtship and mating rituals most intricately. So naturally, the male is tasked with wooing the female into mating. 

From performing headstands to flaunting all the fins, he’ll leave no stone unturned. 

The male is also entrusted with finding a suitable mating spot and cleaning it spotless to lay the eggs. This is where the tiles and pots you placed earlier come into play. 

When the big day finally arrives, the female will drag her ovipositor over the chosen surface in a zigzag fashion and lay up to thousands of eggs. The male quickly follows suit and releases milt to fertilize the eggs. 

The eggs will hatch in the next 6-7 days.

Preparing The Fry Tank 

You can leave the eggs to hatch in the breeding tank and let nature take its course. However, it comes with certain risks. For instance, the newly hatched larvae can be annihilated immediately by the powerheads or pulled into the filtration system. 

I’m sure that’s not what you want. Instead, what you’d want is to prepare a 10-gallon tank for the eggs to hatch in and larvae to grow.

Get a 10-gallon tank and paint all sides black. Or you can use black cardboard or construction paper. 

Next, equip the tank with a 100-watt heater, a sponge filter, an air stone, and an LED hood. 

Once the tank is fully prepared and cycled, remove the clay pot/tile with eggs nimbly and transfer it to the new tank. Don’t overthink this step. If you do, you’ll mess it up. 

The final step is to turn off the tank and room’s light and wait for the magic to happen. 

Next morning, don’t barge into the room and turn on all the lights. You can scare the fry to death. Instead, check the tank using a dim torchlight. If everything went right, you should now see hundreds of wriggly fry swimming in all directions. 

Caring For Clownfish Fry

A clownfish’s development goes through 4 distinct stages: egg, larvae, juvenile, and adult. 

The eggs are transparent and elliptical. They are around 3-4mm in size. 

When the eggs first hatch, the fry have advanced alimentary canals. And they feed on the nutrient-rich yolk sac for around 3 days. 

The third to fifth days are when they’re most prone to starvation. Therefore, you should closely monitor their diet during this period. 

Tint the tank green using liquid algae and add rotifers to feed the fry. 

From the fifth day onwards, they can have baby brine shrimp. 

Metamorphosis usually happens on the 10th day. And the fry are ready to move into the grow-out tank by the 20th day. 

Frequently Asked Questions 

Credit: Christian Gloor (CC License)

Do Clownfish Have Long-Term Mates? 

Yes, clownfish most definitely have long-term mates. It’s not like they spend the rest of their lives alone if a partner dies. But once they choose a partner, they stick with it for as long as possible. 

Do Clownfish Change Gender?

Yes, clownfish can change gender. They’re one of roughly 500 fish species that can change gender. Clownfish are born with both male and female reproductive organs. And when the suitable time arrives, the testes dissolve, and ovaries grow as the fish’s biological change is governed by hormonal change. 

Keep in mind that the clownfish’s DNA itself doesn’t change. However, the expression of different genes changes radically.

The most significant change happens in the set of genes involved in the expression of hormones that regulate gonad’s functions. However, these changes don’t happen overnight. 

The latest research has shown that the transition from male to female first happens in the brain. After that, the transformation of gonads is only involved in later stages. Usually, it takes months or even years. 

If you are interested to read more about these gender-bending marvels, I’m sure you’re going to love this article. 

Related: Can Clownfish Change Gender?

What Is It Called When Clownfish Change Gender? 

All clownfish start out as males. Then, if the opportunity arises, they transition into females. This process is known as sequential hermaphroditism. And it makes clownfish sequential hermaphrodites. 

The Biggest Clownfish Will Always Become Female. Is It True?

Yes. Size really does matter when you are a clownfish. The biggest fish is almost always the female. Mind you, she’s pretty broad and bulky compared to her male counterparts. 

And as you already know, the second biggest fish will be the breeding male. 

As I said above, there’s an average difference of 10mm in size as the pecking order descends. 

Can You Keep A Single Clownfish?

Yes, you can keep a single clownfish without any hiccup. However, they are social fish that love to live in small groups. Therefore, if possible, it’s always better to raise a pair of clownfish if they pair up. 

Clownfish don’t necessarily feel sad and lonely when kept alone. But they’re definitely a lot more active when kept in pairs or groups. So it would be fun to watch their antics for you too. 

Final Words: Do Clownfish Mate For Life? 

Clownfish have one of the most intriguing social systems we know so far. From changing sex to maintaining a strict size-based hierarchy, you’d be filled with amazement once you know what these fish are capable of. 

Do clownfish mate for life? Yes, they do. The biggest fish in the group turns into a female, and she breeds with the second biggest fish, who we can refer to as the breeding male. 

The alpha female and beta male stick with each other for a long term until one of them dies. 

If the alpha female dies, the beta male will change his sex and become a female. ‘She’ will then mate with the next biggest fish in the pecking order. Yep, that’s how it works! 

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rohit gurung author at urbanfishkeeping

About Rohit Gurung

My never-ending love and fascination with Aquascaping started when I received a red-eared turtle for my 10th birthday.

Apart from researching and writing, I spend hours gazing at my 3 turtles. And yeah, I bask alongside them too.