The 30 species of clownfish or anemonefish belong to the Amphiprioninae subfamily of the Pomacentridae family. Species such as Amphiprion ocellaris are popular in salt water aquariums due to their various striking colourations, hardiness,fascinating symbiosis with anemones and their readiness to breed in captivity.
Clownfish can be found in the reefs of the Indo-Pacific. In the wild they will form a symbiotic relationship with sea anemones, using them for shelter. Usually an anemone’s stinging cells called cnidocytes would trigger and deter any intruders that touch it, but clownfish possess a mucus that coats their bodies which prevents anemone cnidocytes from stinging them. The anemone also benefits from its relationship with the clownfish, as the fish will remove parasites, provide better water circulation and also provide nutrition through its excrement. In the aquarium, if an anemone is not available, many clownfish species will choose corals as hosts.
In our last blog post about the longnosed hawkfish, we talked about how they can change sex from female to male. Clownfish are also hermaphroditic, but instead of being protogynous like the longnosed hawkfish, they are protandrous,they can change sex from male to female if the situation suits it. If the female in a group is removed, the largest male will change sex and rapidly increase in size to replace her, while other subordinate males will also increase in size to fill in the gaps made. Because they are found in warm tropical waters, clownfish will typically spawn year round, which gives anyone with a breeding pair ample opportunity to raise their own clownfish straight from the egg.
The female uses her ovipositor to deposit eggs on a nesting surface which the male has cleared, and depending on her size and experience, can deposit over 1000. The male follows close behind the female, fertilizing the eggs as they are laid. Incubation of the eggs takes six to seven days, depending on the temperature of the surrounding water. During this time the male protects the nest from predators and fastidiously fans the the eggs with his pectoral fins, providing a flow of water to keep them clean and to prevent fungal growth.
Larval clownfish are approximately 3 to 4 mm in length when they hatch, they also have a small mouth gape of around 250 µm. Clownfish larvae’s small mouths limit the type of food that they can ingest, and many novice breeders have lost their hatches by not having the right food available. During the first two weeks of their lives, clownfish larvae will eat rotifers; typically measuring 90-160 µm, they are the perfect size to provide a meal. Another hurdle that breeders must overcome is nutritional insufficiency, which can be achieved by feeding the rotifers the larvae eat nutritional food. Feeding rotifers phytoplankton such as Tetraselmis sp. and Nannochloropsis sp. loads them with important essential fatty acids which benefits the clownfish and allows for normal growth. As the larvae grow, so does their options for food as they are able to incorporate larger prey such as copepods into their diet.
Copepods are a natural prey item for wild clownfish and are a great source of nutrition for both growing larvae and adults, as the different life stages provide a wide array of different sized prey. Copepods are rich in highly unsaturated fatty acids (HUFAs) compared to other live feeds while also providing high amounts of protein, and a good amino acid profile. Copepods also contain higher levels of digestive enzymes which the larvae can utilize to process their food, as they do not have well developed digestive systems during that stage of life.
With the right food you can significantly increase the survival of your baby clownfish and have the satisfaction of knowing that fish you helped to grow are swimming in your or someone else’s aquarium.
Ignatius, B., Rathore, G., Jagadis, I., Kandasami, D., Victor, A.C.C, 2001. Spawning and larval rearing technique for tropical clown fish Amphiprion sebae under captive condition. Journal of Aquaculture in the Tropics. 16(3):241-249
Fautin, D.G., Allen, G.R., 1992. Field Guide to Anemone Fishes and Their Host Sea Anemones