You Are What You Eat or How Did the Clownfish Get Brighter Stripes?
A classroom activity based on the senior project of Gordon Richard Lorenson
May 2006 | Advisor: Dr. Sara Lindsay


Tank Raised Clownfish

The ever increasing trade in coral, reef fish, live rock, and other reef organisms contributes significantly to the decline and destruction of coral reefs. Many marine species marketed in "tropical fish" stores are collected by destructive methods, such as using dynamite to stun fish, collecting live rock, and using cyanide to poison fish, that are extremely harmful to their reef home. Wild fish captured by these methods also tend to have a very low survival rate after collection because they are stunned or harmed during collection which causes death during the transportation period.

A recent program (see link below) at the University of Maine is attempting to reduce the need for the wild harvest of tropical reef fish by raising fish in captivity. Fish coloration is important to the attractiveness and can affect the marketability of fish raised in captivity. Along with good vibrant color, good health and size are also key factors important to the sale of these fish. A large number of studies have shown that natural diets available to fish can impact their coloration and growth. A major challenge for aquarists interested in culturing ornamental reef fish as an alternative to wild harvesting is to produce fish that have the same vibrant colors as those found in the wild.

Carotenoids

Nearly all living things obtain their color from natural pigments. Some of the most common natural pigments are compounds known as carotenoids. Carotenoids are responsible for many of the red, orange, and yellow hues of plant leaves, fruits, and flowers, as well as the colors of some birds, insects, fish, and crustaceans. Some familiar examples of carotenoid coloration are the oranges of carrots and citrus fruits, the reds of peppers and tomatoes, and the pinks of flamingoes and salmon.

Carotenoids are fat-soluble pigments often found in plants, algae, and some types of bacteria, where they are important to photosynthesis. Generally, animals cannot make their own carotenoids and instead obtain these pigments from their diet (you are what you eat). Thus, a flamingoe’s feathers and salmon’s flesh is only pink or reddish if they obtain carotenoids in their diet.

Carotenoids and Clownfish

The bright and intricate coloration of ornamental fish is the major reason these fish species are being exploited from tropical reefs around the world. High-quality coloration in the clownfish is very important to sales and trade of these fish. Typically, aquarists check to see that fish have good color (pigmentation), followed by good body shape, fin shape and body size. Clownfish, like other animals, cannot produce their own carotenoids and these compounds must be supplemented through their diet. Fish in their natural habitat tend to consume plants and organisms containing carotenoids. Captive raised fish must be fed diets that contain these carotenoids in order to develop bright colors.

The project you are embarking on asks what affect carotenoids have on the color of clownfish (species name Amphiprion ocellaris) by feeding juvenile clownfish diets that have very different nutritional profiles. Methods for raising clownfish in captivity are well-established and include a variety of diets that promote growth and survival. More information on the source of fish at the University of Maine can be found here.

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