Fishy fact: All clownfish are born male! 

Have you seen the famous Disney movie "Finding Nemo"? Well, let us tell you that they got one not-so-minor detail about clownfish completely wrong. Well, here is a simple fact that they missed! All clownfish ( Nemo and Marlin are clownfish) are born male and the dominant male of a group turns into a female when the female of that group dies.  

Now, if this is the way it should happen, then in the movie Nemo’s dad Marlin should have become his new mother after his birth mom Coral died. Then she would have picked Nemo as her mate! Sounds all messed up, isn’t it? 

Let us make it easy for you. Clownfish, also known as anemonefish, are sequential hermaphrodites. That is, they first develop into males. In fact, they live in regimented schools made up of all males and just one female. This single female is the dominant and generally the largest fish in a given school/group.  

The second in command of the school is usually the largest, and most aggressive male in the group. Due to his dominance over the other males, he tries to ensure that other males stay small by taking the best food opportunities for himself.  Besides the perks of getting more food, he’s also the only one that gets to breed with the only female in the group. 

Once the female lays eggs, which may number even in thousands, the male fertilises them. He eats the eggs of poor quality and guards the good quality eggs waiting to hatch. The baby fish once born ascends to the surface and feeds on plankton until maturation.  

This is the normal process of reproduction that clownfish follow. However, there is a catch.  

If the female of the group dies, the dominant male (who was second in charge) will get the first choice of food and begin to gain weight, ultimately becoming female.  She will then choose a breeding partner among the available males, which is again usually the largest and most aggressive male available and the cycle continues. 

How did the clownfish evolve to change sex? 
We are sure you would like to know how this colourful fish got this magical trait of managing its own sex.  

Well, it is thought that this peculiar ability to change sex developed because, unlike many other types of fish, clownfish rarely stray very far away from their homes among sea anemones (a group of predatory marine animals), who give them shelter. Thus, if they did not have the ability to adapt to potentially limited mating partners in their local area, they may not get a chance to breed at all.  

Quick Facts: 

• Other sea creatures that are known to change their gender include wrasses, which is a type of fish, and moray eels.  Unlike clownfish, wrasses switch from female to male. 
• Clownfish live in warmer water regions in the Indian and Pacific oceans.  They can particularly be found in the Great Barrier Reef and the Red Sea. 
• Clownfish communicate by making popping and clicking noises.  
• Clownfish are omnivores.