Marine biologists are working to breed fish to avoid poisoning reefs with the cyanide often used by fish collectors.
Most saltwater fish sold in pet stores come from reefs in Indonesia and the Philippines, where fishermen stun the colorful dwellers with squirts of sodium cyanide. The potent nerve toxin causes the fish to float up out of the reefs so they can be easily scooped up, but it can also injure or kill them as well as trigger coral bleaching.
"What I find ironic is that people love the ocean. They want to keep a slice of it in their living room. But they're killing the coral reefs," says Soren Hansen a co-founder of Sea and Reef Aquaculture, LLC, in Franklin, Me., one of only a handful of saltwater fish farmers in the U.S.
Why not breed the saltwater fish on farms everywhere? Most fish in freshwater tanks--which are much more common, less expensive and easier to maintain--are indeed farm-raised. But breeding saltwater fish in an industrial aquaculture facility requires re-creating the coral reef ecosystem, a technology that is just moving out of its infancy.
1,500 or more species of saltwater fish sold in stores are caught live in the ocean. Farmers have had very limited success in breeding pelagic fish, which account for 90 percent of all tropical saltwater species. Pelagic fish spawn and then abandon their young. Larvae lack mouths, eyes and guts and are so fragile that colliding with an air bubble could kill them.
A key challenge has been figuring out what to feed young saltwater fish. Unlike freshwater tank fish, which readily devour processed flake food, tropical saltwater fish prefer to eat their meal while it is still flapping. Luckily, breeders found that many demersal fish eat freshwater rotifers--microscopic animals that clone themselves every 24 hours and require little space. The demersal fish fare even better when the rotifers are soaked in nutrient-rich fats and proteins found in the sea.
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.
Improvement is urgently needed. The demand for tropical saltwater fish soared in 2004, when Finding Nemo--an animated movie about father and son clown fish, Marlin and Nemo--prompted a buying frenzy. "Every kid wanted a Nemo and Dory [a regal tang that also stars in the movie] in their fish tank," recalls Andrew Rhyne, a marine biologist at Roger Williams University in Bristol, R.I.. No one thought to measure the change in the number of wild-caught fish, Rhyne says. But clown fish sales at the world's largest fish hatchery--Ocean, Reefs & Aquariums
in Fort Pierce, Fla.--jumped 40 percent.
Retailers are preparing for another sales spike this fall, when Finding Nemo 3-D
will be released. Luckily, clown fish are among the few tropical saltwater fish that breed in captivity. Like most demersal fish--those that spawn on hard surfaces--parents stick around to care for their young. Demersal larvae also emerge as fully formed miniature fish, making them relatively self-sufficient. Hobbyists have been breeding clown fish by trial and error for decades. These days, Hansen says, clownfish account for about 80 percent of all tropical saltwater fish sales.
Perseverance will be key to expanding tropical saltwater 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 has 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. Captive bred fish are used to the captive environment. They'll eat anything you throw at them. They're bulletproof."
(via Scientific American