22 Dec 2014
Helping Your Aquarium and Coral Reefs, Too
Finding Nemo, the smash hit Pixar-animated movie released in 2003
by Walt Disney Pictures, begins with the capture of a young clownfish from
Australia’s Great Barrier Reef for display in an aquarium in a dentist’s
office. Adventure follows as Nemo’s father, Marlin and another fish, a regal
tang named Dory, set out to find and rescue him.
Finding Nemo is fictional, but clownfish are by far the most popular ornamental fish used in salt water tanks. Until recently, they and many other types of ornamental fish had to be captured from coral reefs in Thailand, Indonesia and elsewhere. That trade provides income for some coastal fishermen, and the Ocean Health Index measures the amount and sustainability of that trade as part of the Natural Products goal.
Reef fish typically produce more young than will
survive, so in theory some surplus individuals can be caught. If capture does
not harm them or other reef dwellers and enough fish remain to supply the
reef’s ecological needs. Under those conditions the harvest should be
Unfortunately, collectors often use sodium cyanide poison or dynamite explosions to stun fish so they can be collected more easily. Those (usually) illegal techniques needlessly kill many fish, along with other reef dwellers and portions of the reef itself.
To satisfy the demand for aquarium pets in an assuredly sustainable way, scientists and entrepreneurs are now growing clownfish in culture facilities so that wild specimens don’t have to be caught. This could increase the health of reefs (though it could also decrease the income of coastal harvesters).
Professor Min Liu, a marine scientist at Xiamen University, produces thousands of clownfish each month for sale to Chinese aquarium owners---and not all of them look like Nemo. Among the thousands of fish in her tanks a few will be slightly abnormal in color and pattern. On the reef, such variants might have lower survival because predators could spot them more easily, but in the lab they have a better fate. Prof. Liu and other breeders select those variants and breed them separately from the others. Repeating that selective breeding over a number of generations produces new types of clownfish that add beauty and variety to an aquarium.
In the U.S.
marine biologist Søren Hansen’s company, Sea & Reef Aquaculture,
located at the University of Maine’s Center for Cooperative Aquaculture
Research, has selectively bred more than 40 distinctly different types of
clownfish, all raised from eggs spawned at the research center.
Denizens of coral reefs would be amazed to see these new forms, such
as ‘DaVinci ocellaris’, ‘Black Photon’, ‘Phantom’, ‘Lightning Maroon‘ and ‘Frostbite’
(shown below, all photos ©Sea&Reef Aquaculture), as they
have probably never occurred naturally (all photos .
Sea & Reef already sells nearly 20,000 tropical fish each month,
but Hansen has a bigger goal: growing every kind of ornamental marine animal
needed for a marine aquarium, including corals, anemones, shrimp and sea
horses, so that no wild specimens would have to be taken from coral reefs or
Culture facilities for clownfish and other tropical ornamentals are also developing elsewhere. Korea's Corea Center of Ornamental Reef and Aquarium (CCORA) grows 16 species of clownfish and sea horses (which are also used for Chinese traditional medicine) and is working to produce other aquarium ornamentals. Clownfish are also growing in the desert at Israel’s Arava Research and Development Center, which is scaling up closed-cycle culture to produce them and other species for the aquarium trade.
In addition to relieving stress on coral reefs, there are other good reasons for aquarium owners to display cultured clownfish. Less stress during capture and shipping keeps fish healthier and reduces mortality. Cultured fish are also more accustomed to captivity, people and artificial diets, so they are calmer than wild fish and make an easier transition to the aquarium environment. A wild clownfish usually lives in association with a sea anemone, gaining protection from predators by living among its stinging tentacles and fiercely defending that territory against others. In contrast, cultured clownfish are used to company because they are raised in large groups without anemones. If young clownfish are put into a tank at the same time and there are no anemones to fight about, they live together peacefully. In the predator-free aquarium the a clownfish survives perfectly well without an anemone.
Finally, just as garden owners enjoy a selection of flower varieties far beyond what has evolved naturally, the large (and growing) diversity of clownfish colors and patterns available from growers far surpasses what nature has produced. Since the aquarium is an artificial environment anyway, growing and displaying these new forms does not seem inappropriate---and it probably helps to preserve the spectacular beauty of coral reefs in the wild.