Marine Species: Clownfish

Made even more popular by the movie “Finding Nemo,” the iconic clownfish is one of the most frequently seen fish when diving in the Indo-Pacific and Red Sea. Although they’re quite common, they’re no less fascinating.

Clownfish are so common in tropical environments that a lot of divers don’t give them more than a passing glance. But not only are there a wide variety of these photogenic fish, some of their features are quite surprising if you take the time to learn.

What are they?

Clownfish, also known as anemonefish, have a symbiotic relationship with anemones. The clownfish is perfectly safe nestled in the tentacles of its host anemone, poisonous to all other fish. The anemone provides shelter and protection, while the clownfish helps attract prey and also gets rid of parasites for its host.

Scientists have identified 30 different clownfish species. They can range from black, to orange or pink, often with distinctive white stripes. Size varies from two to six inches (five to over 15 centimeters).

Anemonefish feed on plants and animals, such as small mollusks, plankton and algae, depending on what’s available close to their anemone. They are also prey for a lot of bigger fish on the reef, but their best defense resides in the anemone to which they retreat when they feel threatened.

Where are they?

You can easily find clownfish in the Indian and Pacific Oceans, as well as in the Red Sea, although there are none in the Atlantic Ocean. These fish usually like shallow waters, and you’ll usually find them very close to their home anemone. They tend to stay close to their host, and can sometimes be a bit defensive if you encroach too closely on their territory. They are harmless to humans given their size.

Collectors also commonly seek clownfish for aquariums, which has unfortunately led to a population depletion in some areas.

Why are they interesting?

Clownfish have a very strict hierarchy — for once, the biggest female is the boss. The biggest male is the reproductive partner and only the two biggest fish in the anemone will mate. Clownfish are sequential hermaphrodites, meaning that they change sex during their lifetime. If the biggest female disappears, the largest male will become a female. Afterward, another male will take his former place in the hierarchy. There can be competition within the same anemone host, but usually the hierarchy is well-respected.

Clownfish lay eggs on a flat surface close to their anemone, which hatch about a week later. The male parent acts as the main guard for the eggs. Usually they lay hundreds of eggs, and the newborn little clownfish will have to go and find an anemone for themselves.

This photogenic fish is a favorite among many underwater photographers; perhaps next time you see one, you’ll give them a closer look or try to spot their eggs close by.