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CRITTER: Meet kikakapu, the threadfin butterflyfish

Kikakapu, the thread-fin butterfly-fish, is one of the most-common coral-reef fish throughout the tropical Pacific, Indonesia, Africa and the Red Sea.

This fish has many different names, from cross striped butterfly-fish, whip butterfly-fish to its Middle Eastern name of Sham el-Sheikk. The thread-fin butterfly-fish is so widespread in tropical water because it has a wide variety of food it can eat, from algae, coral polyps, shrimp, worms and floating zooplankton.

In Hawai‘i, this 7-inch-long fish is super-important to the health of the coral reefs.

You normally see it in pairs feeding in shallow water down to about 60 feet deep. Kikakapu helps keep the reef clean. It will feed on sick and dying coral polyps, which allows new corals to grow. The name “kikakapu” in Hawaiian means “strongly forbidden.” The Hawaiians knew that removing this fish from the reef would cause the corals to get sick and die.

Us marine biologists use this fish as an “indicator species.” When we do coral-reef surveys we count how many kikakapu are in one section of the reef, called a “transect.” The more butterfly-fish we count means there is more healthy coral.

The thread-fin butterfly-fish is a ray-finned fish with “chevron” markings. They have a long, thin dorsal fin that looks like a thread, and their pattern of crossbars confuses predators when they are being chased. These fish are very popular in the aquarium trade, and can live up to 8 years in captivity. They cost over $60 each, and aquarium-fish collectors in some places have caught so many of them that the coral reef gets covered in algae and dead coral polyps and dies!

It is super-fun to have a saltwater aquarium filled with beautiful fish, but removing these fish from their native coral reefs can destroy the marine ecosystem. It is important to learn how to captive-breed these fish and supply the marketplace so no one needs to take them out of the wild. All tropical fish can be captive-produced, but that may take time and money to figure out the process. But the rewards to the captive breeder and the environment are huge!

You can see kikakapu in action in my movie “The World’s Guide To Hawaiian Reef Fish” on my web at, and also follow my YouTube channel at Underwater2web, where I release a new “kid-friendly” marine-life and surf movie every week!


Terry Lilley is a marine biologist living in Hanalei. He is co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to
Source: The Garden Island

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