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Moorish Idols

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Thursday, November 08, 2007


They are the streamer dancers of the underwater world. Moorish idols, Zanclus cornutus, have long flowing dorsal fins that flutters around in the water in a captivating dance as the fish swims through the water. For this reason and their gorgeous yellow, white and black coloration, they are very popular fish to have in aquariums. However, they are infamous for being hard to keep. Remember Gil the moorish idol from the movie Finding Nemo? Gil had a damaged pectoral fin and a scar on his face. This is an inside joke among aquarists because it is believed that all moorish idols must be have been traumatized at some time in their lives. I was surprised when I first found out that the Aquarium has an entire school of moorish idols hanging out at Shark Lagoon.

The first thing that came to my mind was the stress factor. When a fish’s environment is not up to its standard of living, the fish can become stressed. Too much stress can kill the fish. Common stressers include poor water quality, trauma, aggressive roommates etc. The moorish idols at Shark Lagoon share the same exhibit space as 200 sharks. I don’t think I need to explain why living with sharks could be stressful. Plus, thousands of people reach into the exhibit everyday. How would you feel if thousands of giants reached their hands into your house everyday? I think that would be stressful. And yet despite it all, the moorish idols aren’t just living, they are thriving!

The best thing that living in Shark Lagoon does is it allows the moorish idols to exhibit their natural feeding behavior. In the wild, moorish idols do not eat large meals and fast afterwards like some fish. Rather, they are eating all the time and they do this by perpetually foraging for food. A little nibble here, a little nibble there on anything and everything. Therefore, rather than feeding them on a set schedule, the moorish idols are placed in an environment where food is plentiful all the time. Shark lagoon is exposed to the sun which allows algal growth and thus provides veggies for the moorish idols. Because it is a well aged exhibit, Shark Lagoon has lots of invertebrates like isopods, tubeworms, copepods, atapsia anemones etc. living in it. These little invertebrate snacks, along with any scraps the sharks may have left in the exhibit, provide the protein the in the moorish idol diet.

As for the stress… they just get used to it. Over time, the moorish idols have gotten used to living along side sharks and people’s hands. And it helps a lot that our staff and our guests cooperate to keep from touching the fish and instead reach gently in the water with two fingers to touch the sharks. The water quality in Shark Lagoon is great so that is never a problem, and in fact, the moorish idols help it with their constant nibbling. Overall, life is great for the moorish idols living in Shark Lagoon.

Moorish Idols
There are four moorish idols at shark lagoon and they usually stick together.  | © David Chen
Moorish Idols
When the staff flip over any rock in Shark Lagoon they find lots of little critters crawling around. These little invertebrates provide nutrition for the moorish idols.  | © David Chen
Moorish Idols
The dorsal fin of the moorish idol is very long. So long in fact that the fin did not fit in this picture. As the fish swims, the fin trails like a banner.  | © David Chen

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