Clownfish got famous through the movie “Finding Nemo” and possibly every scuba diver loves them. Yet these little orange fish are not just too cute, but also amazingly interesting and weird.
Clownfish Fact 1: There is not the one clownfish
There are 30 known species of clownfish belonging to the family Amphiprioninae. They are beautifully colored in orange, red, yellow or black with white stripes. Depending on the species they can reach a length of 10 to 18 cm.
Nemo and his dad, Marlin, are ocellaris clownfish (Amphiprion ocellaris), also called clown anemonefish or false clownfish.
Clownfish Fact 2: They like it warm
Clownfish Fact 3: Clownfish live in a symbiosis with anemones
Clownfish can always be found in and around anemones. They live in a mutualistic symbiosis with the anemone, meaning both animals profit from living together. Their other common name, Anemonefish, they got from this symbiosis.
Anemones are poisonous fish-eating animals that attach themselves to the ocean floor. As soon as something touches the tentacles a special cell (nematocyst) is triggered and a venom is released in the prey or predator. So they can use the venom as a hunting as well as a defense mechanism.
So what about the clownfish? By building up a protective mucous the clownfish are immune against the stinging cells and can therefore use the tentacles as a hiding place. Inside the anemone the fish are protected against predators. In addition they profit from food leftovers from the anemone.
In return the clownfish keeps the anemone aerated and clean. Through the movement (clowning around) of the fish the circulation of water is increased providing fresh water and with it oxygen as well as a higher amount of food. Also the clownfish eat dead tentacles.
Clownfish Fact 4: They eat everything
Ok, maybe not everything – they are omnivores and besides dead tentacles and anemone food leftovers, clownfish eat algae, plankton, worms and small crustaceans.
The juvenile fish would rather stay within the anemone and eat what they can find there while larger fish start to move further from the anemone to look for food.
Clownfish Fact 5: They are aggressive, not playful
Many divers and snorkelers enjoy to interact with “Nemo”. When approaching the anemone the fish might swim towards you and come very close to the fingers or the face, whatever is closest to the anemone.
This does look like playing. Well, it’s not. The fish defend their home and attack everything that gets too close. How aggressively they attack depends a lot on the species. While some might actually bite you, others rather hide inside the anemone when something gets too close.
I once took a picture of a porcelain crab inside an anemone, not paying too much attention to the clownfish living there too. One of them bit me in my finger – it was actually bleeding and left a little scar.
Clownfish Fact 6: All Clownfish are born as males
Baby clownfish all start their lives as males and only one female lives in each anemone.
When the female dies the largest and most dominant male becomes the female. While the second largest goes through a quick growing period and will then be the large dominant male and the breeding partner of the female.
Clownfish Fact 7: Clownfish are monogamous
Even though there are many male Clownfish living with one female they are monogamous. Only the dominant male is allowed to mate.
Clownfish Fact 8: Clownfish don’t have sex
They reproduce by an external fertilization, also called spawning. The male chases the female to the nest, it previously prepared, where the eggs are laid and the sperm is released.
Clownfish Fact 9: Clownfish produce up to 1000 babies each time
Clownfish lay up to thousand eggs on a clean surface, like a rock, next to the anemone. It takes 6 to 10 days for the eggs to hatch.
Clownfish Fact 10: The male take care of the eggs
The male clownfish does most of the “egg sitting”, while the female helps out from time to time. This job includes aerating (fanning) the eggs, removing unfertilized or unhealthy eggs as well as defending the small Nemos from any danger.
Clownfish Fact 11: Nemo always gets lost
After hatching the clear larvae float away and drift in the ocean for around 10 days. They then get close to the bottom of the reef to search for a new home – a host anemone.
Clownfish Fact 12: They talk to each other
Clownfish might usually not talk as much as Nemo does, but they are still quite chatty. They can click, grunt, pop and chirp.
Researchers (1) compared the noises with specific behaviors in a study and came to the conclusion that the sound could be a strategy to defend and reinforce their social status. The dominant male makes a pop sound while moving aggressively, the smaller fish make a chirp sound and show submissive behavior.
Clownfish Fact 13: Clownfish get collected in the wild to be brought to aquariums
While the movie “finding Nemo” is all about the clownfish and his friends escaping from the aquarium, many people hold clownfish in aquariums at home. Doesn’t that just sound wrong? Still many of these are not bred in captivity, but collected from the reefs. Removing them from the reefs is a threat to the fish and the reefs.
If you ever think about getting your own clownfish make sure it was bred in captivity or better go scuba diving and observe them in the nature. While in captivity clownfish can only survive for 3 to 5 years they can live up to 10 year in the ocean.
Luckily the clownfish are not an endangered species yet.
(1) Eric Parmentier (2012). “Overview on the Diversity of Sounds Produced by Clownfishes (Pomacentridae): Importance of Acoustic Signals in Their Peculiar Way of Life”. In PLOS ONE
(2) Pericula Clownfish in National Aquarium. Retrieved March 07, 2017 from https://aqua.org/explore/animals/clownfish
(3) Amphiprioninae in Fishbase. Retrieved March 07, 2017 from http://www.fishbase.org/identification/SpeciesList.php?genus=Amphiprion