Ironically, Finding Nemo, a movie about the anguish of a captured clownfish, caused home-aquarium demand for them to triple.
A problem is that people who buy them don’t know how to manage a marine aquarium and just set one up like they would a goldfish bowl. This often leads to death of the fish as the owners don’t know how to care for them or a saltwater tank.
Overharvesting and invasive collection methods, such as the use of cyanide to stun and capture fish, are destroying reefs and their inhabitants. In the Philippines and Indonesia clownfish have been severely depleted. Loss of clownfish leaves anemones exposed and vulnerable to predators. When reefs are on their way to destruction, one of the first things to disappear is anemones and their clownfish. Bioligists are not the only ones who see a decline in the wild populations. Divers also reports how much rarer it has become to see clownfish.
In a study done by Dr Billy Sinclair we see that shoals that once numbered dozens of clownfish now only contain a few specimens. This makes it harder for the species to breed. In some area they are probably gone completely. Hopefully populations can recover if the people stop collecting them from the reefs for people's pets.
Some interesting clownfish facts:
Clownfish and certain damselfish are the only species of fishes that can avoid the potent poison of a sea anemone. This is believd to be due to the mucus on the fish. Either the anemone doesn't see them as food from the sugars in the mucus or the fish develop an immunity to the anemone by rubbing them.
Of the thousands of species of anemones, only ten host clownfish. Clownfish spend their entire lives with their host anemone, rarely straying more than a few yards from it. Once an egg hatches if the young fish doesn't find an anemone within a day or two it will die.
Clownfish live in small groups inhabiting a single anemone. All Clownfish are born male. One fish in the group will become female and is the dominant fish in the group. The largest male will be the dominant male and these fish will be the only breeders in the group. In order to assure this, the couple will chase and nip at the other male fish causing stress and reduced energy for food foraging. When the female dies, the dominant male changes sex and becomes the female and the next largest male becomes the dominant male.