That research has led to the successful raising of clown fish on farms. Intriguingly, the fish are also being selectively bred. At his farm in Maine, Hansen shows off his morphs, which include chocolate-brown Maine mocha Nemos, snow-white blizzard Nemos and mind-bending Picasso Nemos. Designer Nemos look cool and retail strong, Hansen says, with hobbyists paying hundreds of dollars for the newest hybrid iteration.
The tools developed to breed the clown fish have recently been successfully applied to several dozen demersal species. But breeders are not anywhere close to domesticating pelagic fish. Because pelagic fish larvae are so tiny, they can only ingest food smaller than 80 microns. (A micron is one millionth of a meter, or about 40 millionths of an inch.) Identifying and cultivating these microscopic food sources has proved difficult.
Several years ago, Baensch bred the pelagic pygmy angelfish by feeding the larvae with copepod nauplii—copepods in their earliest life stage. Besides being extremely small, copepod nauplii are packed with digestive enzymes, an essential ingredient for the gutless larvae.
Baensch initially fed the larvae wild-caught copepod nauplii from the Pacific Ocean. He now cultures the nauplii for the larvae's earliest days, but then switches to wild copepods. Copepods are a challenge, however, because unlike rotifers, they avoid crowded conditions and need time to reproduce sexually. The nauplii also outgrow pelagic larvae within a few hours.
To scale up production of pelagic larvae, farmers must learn how to breed food for them on a large scale. They are making some headway. A team in Italy shrank the copepod's space requirements by raising nauplii in a large tank and then concentrating them in seawater. Hansen, meanwhile, is tinkering with novel nutrition options. In unpublished work, he has cultured a species of zooplankton and successfully reared angel fish larvae on it for 15 days, the duration of his first experiment.
Hansen and others hope that identifying and rearing food for pelagic tropical fish will finally allow farmers to replace the wild-caught fish sold to retailers with species raised in captivity. That change would protect reefs from further cyanide poisoning. "Aquaculture, the way I see it, is the future," says Gayatri Lilley, founder of the Indonesian Nature Foundation, a group dedicated to developing sustainable fisheries in Indonesia. "But [currently] the biology of these reef fish remains too complicated to culture all aquarium species."
Aquaculture is therefore only a partial solution. Lilley dedicates her time to training fishermen to use underwater nets instead of the cyanide method. But the fishermen need to know that buyers will pay a higher price for fish caught using sustainable practices.
Better monitoring of the industry is also sorely needed, such as a labeling system for all fish entering the market that would indicate how they were caught or whether they were farm raised. Right now, says Rhyne and his colleague Michael Tlusty, most tropical fish entering the market simply get coded as "marine tropical fish." That, Tlusty says, "would be like bringing in salmon, pollock and tuna and calling them all seafood."
Perseverance will be key to expanding tropical fish aquaculture. Baensch recalls an experiment in which he started with 100 trigger fish, only to have their numbers dwindle to 12 overnight. "Everything was fine," he says, "until the fish started killing each other." Trigger fish, it turns out, grow up to be highly aggressive adults. But work in clown fish suggests that innate tendencies can be bred out during the domestication process—which can also lead to better pets. Back at his farm, Hansen shows me a tank filled with hundreds of clown fish. They would never school like this in the ocean, he says, adding: "Wild-caught fish come in skittish. They won't eat. They hide in a corner. My fish are used to the captive environment. They'll eat anything you throw at them. They're bulletproof."