Reef Report for Wednesday, July 14, 2004
The Real Home Life of Nemo and Family!
All about Anemone Fish.
Like many people, one of our favorite movies is Disney’s "Finding Nemo". How could you not love a movie about our favorite fish, and our favorite place to dive?
While the movie was amazing, we find the real lives of Anemonefish (also called Clownfish) to be even more amazing and surprising.
There are 28 species of clownfish, and their distribution throughout the tropical regions of the Indian and Pacific Oceans exactly matches that of the 10 species of anemones that they live with.
Clownfish always live in close association with anemones, adult clownfish are rarely, if ever encountered very far away from one that they consider their home territory. Given that anemones do prey of fish and smaller creatures, this association is puzzling; what do these fish gain by living amongst a potential predator?
The key word seems to be protection from other, more effective predators. There is thought to be an interaction between mucus that is produced by the anemone and that of the clownish, and somehow this interaction prevents the Clownfish from triggering the stinging behavior of the anemone.
By darting into the anemone when startled, a clownfish is going into a place where most predators will not.
Emboldened by this great protective scheme, these small fish are fiercely territorial, well beyond their small stature. It is thought that these protective behaviors in turn protect the host anemone from its predators.
The family life of Clownfish is quite unusual by our own standards. Clownfish live in small groups, with largest fish being the sole breeding female of the group. The next largest fish is the sole male of the group; the remainder of the group includes up to four smaller, non-breeding females.
If the breeding female dies, things get interesting really quickly. The male of the group becomes the breeding female, and is able to lay eggs. The largest of the remaining females changes into a male, becomes the father of the next batch of eggs. The remaining females grow a bit larger, and wait their turn in line for the next change in the hierarchy above them.
In usual circumstances, a breeding female clownfish has gone through two changes of gender to reach her current status. (They didn’t show that in the movie, did they?)
Clownfish lay their eggs at the base of the anemone; under the protective tentacles these eggs are safe from harm. Soon after hatching the young are on their own, drifting in the currents. After 8 to 12 days, they develop coloration and behavior similar to adults, and at this time must find a suitable host anemone, or be subject to the many predators of small fish on the reef.
To Learn More:
About the biology of Clownfish.
The weekly reef report is written by Joel Groberg of DiveTheReef.com,
who compiles them from the many conversations he has with dive staff in the area, as well as many other local sources in the dive
Index of all reef reports.