Banggai Cardinalfish: females initiate courtship and males hatch eggs

banggai cardinalfish
Image credit: Boon Ping, aquarist at S.E.A. Aquarium

A curious looking creature, the Banggai Cardinalfish has a greyish-silvery colouration with white-trimmed black stripes on its head and body, and a scattering of white spots on its fins and body. They have a very limited geographic range and can only be found in the waters surrounding the Banggai Islands in Indonesia.

Banggai Cardinalfish typically live in small groups of 2 to 6 individuals. Juveniles are often found sheltering around sea anemones for protection while older individuals tend to be found around branching corals and sea urchins.

Here are more interesting facts about this beautiful fish:

Females make the first move

banggai cardinalfish

After a female chooses a male to mate with, they separate from the group and establish a territory. This pair would aggressively defend their territory from other fish that come too close to them. The female will begin an unusual courtship ritual that is not found in other species of fish: she swims along her mate with their bodies touching and trembling, doing so on both sides over several hours. When his lower jaw begins to darken and he starts to open and close his mouth, it is a sign that he is receptive and ready to mate.

Fathers are mouth brooders

Another behaviour unique to Banggai Cardinalfish: the fathers are mouth brooders. The female will spawn up to 75 large eggs, which are immediately swallowed by the male, and kept inside a special pouch in its mouth. The eggs take approximately 20 days to hatch, and continue to develop in the male’s mouth pouch.

Banggai cardinalfish
Image source

After another 10 days, or when the young fish have reached about 5 to 6 millimetres in length, the male releases them from his mouth. During this mouth brooding period, the male does not eat. He also regularly turns the eggs to provide them with aeration, and removes any dead eggs and embryos. However, after he releases the young from his mouth, he does not interact with them.

They’re endangered

The Banggai Cardinalfish are currently listed as Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

banggai cardinalfish

According to a survey in 2015, only 1.5 million Banggai Cardinalfish remain in the wild. Reason being they are found in relatively shallow calm waters which makes them extremely easy to catch. Fishermen sell these beautiful ornamental fish by the thousands for as low as 5 cents per live fish! However, it is estimated that only 25% of fish caught will survive to be sold in markets across Europe, the United States and Asia.

The habitats of these coral fish are very susceptible to ecosystem degradation and pollution, thereby reducing their numbers as well. As such, it is important that we step up breeding efforts across the world to meet the demands of the aquarium trade, while reducing the fishing pressure on wild populations.

They’ve been successfully bred at S.E.A. Aquarium

Here at S.E.A. Aquarium, we have successfully bred these beautiful fish, with 150 babies hatched in 2016 alone. Last week, we welcomed a new brood of babies. These tiny babies are currently in our back-of-house area where they are undergoing further observation. They will go public when they grow to a more appropriate size.

These babies are only about 3mm-5mm long. Image credit: Boon Ping

In the meantime, you can see the adults in our Focus Globe Habitats.

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