March 2004
Saving Nemo
Aquariums, once water-filled cabinets of curiosities,
exert potent economic forces that can
foster conservation in the wild.
By Melanie L. J. Stiassny
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It is unlikely, of course, that hers was the first aquarium. Fishes have been kept and bred for millennia, for food as well as amusement, but the ancient origins of the practice are obscure. Perhaps the Sumerians were the first fish keepers; certainly the manipulations of carp and goldfish by the Chinese, and later by the Japanese, are of ancient lineage. And a Roman notable, Quintus Hortensius, is reported to have wept when his favorite eel died in captivity.
But today’s fish tanks were far beyond the reach of Mme Rondelet and her contemporaries—to say nothing of the ancients. For one thing, plate glass was not available until the late seventeenth century. More important, though, was the lack of the most basic understanding of the relations between aquatic plants and animals, the cycling of nutrients, or practically any other detail about the ecology of a healthy aquatic community.
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In any event, the keeping of fishes as household pets did not become popular until the first half of the eighteenth century, and the first public aquariums appeared in Europe only in the early 1850s. By 1928 some forty-five public or commercial aquariums had been installed worldwide, and today many towns and cities have aquariums that attract hundreds of thousands of visitors a year.
As for the popularity of fishes kept as pets, in the United States they rank behind only cats and dogs. More than 7 million households give fishes a home. For some people the animals are just color-coordinated living furniture. But for others, the family fish tank is a living laboratory that ignites the first spark of scientific curiosity and engenders an enduring love of nature.
But the popularity of fishes cuts two ways. On the one hand, public aquariums and the practice of keeping tanks at home increase people’s awareness of aquatic nature. The resultant demand for aquatic organisms to fill the tanks creates livelihoods for animal suppliers, and the proceeds from the trade are particularly welcome in low-income coastal communities in the tropics. On the other hand, the burgeoning demand for live fishes and invertebrates can put heavy pressures on tropical ecosystems. Yet the tension between keeping up with demand and maintaining the ecosystems that supply it need not become a wasting, zero-sum game. If the methods for harvesting animals from tropical ecosystems are managed carefully, suppliers will be able to provide lively displays for fish tanks in the dentist’s office, while helping ensure that the source populations continue to thrive in the wild.
| To fill public aquariums and private tanks, large numbers of wild animals are taken from the sea, mainly from reefs. Some 24 million ornamental fishes, 12 million pieces of coral, and 10 million ornamental invertebrates are sold each year, and many more die along the way. |
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On any list of the roles and cultural value of aquariums, entertainment must rank high. In North America alone some 134 million people visit the 200 or so accredited institutions of the American Zoo and Aquarium Association each year: more people than attend all major-league sports venues combined. And beyond pure entertainment, who would dispute the atmosphere of relaxing serenity aquariums have to offer, the opportunity to contemplate the otherworldly grace and beauty of the aquatic realm? Aquariums afford access to worlds that we, as terrestrial creatures, must share, yet rarely glimpse. Moreover most large public aquariums are not only responsive to the entertainment value of healthy animals, but fully committed to educating their visitors about the aquatic environment, its fragility, and the need for its conservation.
Large public aquariums can also play direct roles in conservation, in addition to their educational one. Some have breeding programs for marine mammals, invertebrates, and other species, including a few marine fish species they can raise in captivity. Many channel funds to reserves, parks, and other conservation programs in the field.
Still, probably the most consequential effect of aquariums is via their role as economic engines; that is particularly true for small, privately owned fish tanks in businesses and homes. The annual trade in live marine animals is estimated to be worth between $200 million and $300 million, and still growing. Such figures translate into large numbers of wild animals taken from the sea, mainly from reefs: some 24 million ornamental fishes, 12 million pieces of coral, and 10 million ornamental invertebrates are sold each year, and many more die along the way.
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The trade in freshwater organisms is even larger than the marine trade. But the freshwater trade relies heavily on animals raised in captivity. Freshwater fishes, by their very nature, are already adapted to life in relatively contained habitats. Their eggs tend to be large, well provisioned, and they sometimes even get parental care. Marine species, by contrast, tend to deposit, fertilize, and then abandon their small eggs to their fates. When the eggs hatch, the tiny fry generally have a protracted larval stage, during which they are dispersed over large ocean areas as plankton. Thus the larvae of most marine fish species are smaller, less hardy, and more difficult to feed than their freshwater counterparts.
As a result, freshwater fishes tend to fare much better when raised in tanks than marine species do. As many as 90 percent of the freshwater fishes commonly found in aquariums have never known a river or a lake; most have been reared in large facilities in Singapore or Florida and can no longer even be considered wild animals. Ironically, in fact, many freshwater habitats have become so degraded that some species are more common in dentist’s offices than they are in the wild—some species of African lake cichlids fit into this category. A few species of pupfish are actually extinct in nature yet thrive in household aquariums.
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The freshwater trade relies heavily on animals raised in captivity. Freshwater fishes, by their very nature, are already adapted to life in relatively contained habitats. Their eggs tend to be large, well provisioned, and they sometimes even get parental care. |
The great majority of animals in the marine trade, however, must be systematically hunted and taken from the wild. Of the 1,500 marine fish species that are regularly traded, only about seventy have been successfully bred in captivity. And of those seventy, only a handful are currently raised in quantities viable for commercial use.
Compounding the difficulty of captive breeding is the fact that most marine fishes are taken from coral reefs, themselves among the most endangered of marine habitats. Although reefs account for just one-quarter of 1 percent of the marine environment, they are home to some 4,000 marine fish species, or roughly a third of the total. Reefs also harbor some 800 reef-building coral species, and innumerable other invertebrate species. Yet coral reefs are threatened by a deadly mélange that includes global warming, coastal development and runoff, marine pollution, destructive fishing practices, and overexploitation.
The nature of the marine fisheries trade presents government regulators and conservation advocates with something of a dilemma. As I noted earlier, the trade is an important industry for residents of coastal communities close to coral reefs, communities that are generally impoverished.
In Finding Nemo, a father-son fish tale, a young clownfish is kidnapped from the family’s anemone home by an oblivious scuba-diving dentist. The story follows the adventures of Nemo’s timid dad, Marlin, who sets out to rescue his son. |
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At least now the data shortage has been corrected. A new report, From Ocean to Aquarium: The Global Trade in Marine Ornamental Species, published in 2003 by the United Nations Environmental Program (UNEP) and its biodiversity and policy implementation arm, the World Conservation Monitoring Center (WCMC), is a thoughtful and data-rich synthesis of the issues. Much of the data I mention here comes from this report (available online at www.unep-wcmc.org/resources/publications/WCMC_Aquarium.pdf; document takes a few moments to load).
When I first read the UN report I was struck by a certain pleasant happenstance. Its publication coincided with the nationwide release of the animated feature film Finding Nemo. In the story, a father-son fish tale, a young clownfish is kidnapped from the family’s anemone home by an oblivious scuba-diving dentist. The story follows the adventures of Nemo’s timid dad, Marlin, who sets out to rescue his son from incarceration in the dentist’s dismal office in Sydney, Australia. It occurred to me that at the same time Marlin was trying to find Nemo on the silver screen, the new UN report was offering real insights into how the rest of us can save Nemo—or at least his kind.
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Worldwide there are twenty-seven species of clownfish in the genus Amphiprion, and, according to the report, about fourteen of them are regularly raised in captivity (which makes them a rarity among marine aquarium fishes). Clownfishes, as the movie suggests, have a special symbiotic relation with certain species of sea anemone. Anemones, together with organisms such as corals and jellyfishes, are cnidarians; like their relatives, anemones have tentacles covered with harpoonlike stinging capsules called nematocysts. The stinging cells can cause plenty of damage to the anemones’ predators and prey alike, but clownfishes are immune to the stings of their home anemone.
Whatever the source of this immunity, it enables each clownfish to swim freely among its home anemone’s tentacles. That provides the fish with a safe haven and a home for life. And in return, the fish helps protect its host anemone from predators. Most clownfishes are hardy and relatively easily kept in a fish tank; as a result clownfishes have become popular pets. Thousands of anemones and more than 145,000 of one particular fish species, the clown anemonefish (A. ocellaris) are sent to market each year. Ironically, given the conservation message of Finding Nemo—that life in the wild is better than incarceration in a tank—sales of clown anemonefish and similar species rose considerably after the film opened, according to Paul Holthus, president of the Marine Aquarium Council in Alexandria, Virginia.
That unintended consequence notwithstanding, there’s a great deal to like about Finding Nemo—both in its conservation message and in its wonderfully animated and entertaining story. But I can’t restrain myself from two ichthyological asides. The first is about the film’s anthropomorphic characterizations. In a crucial scene of the movie, Nemo’s mother and his unhatched siblings are eaten by a barracuda. Nemo is the lone larva to survive. Nemo’s father becomes an overprotective worrywart after the disaster, and both quite evidently miss Nemo’s mother very much.
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Had Marlin, Nemo’s dad, just hung around for a while, he would have become a she and Nemo would have had his mom back. Then, with time, Nemo himself would have matured into a functional male, and . . . but perhaps that’s all a bit too dark for the story line. |
The trouble with all this understandable humanizing of the characters is that in nature, clownfishes are protandrous hermaphrodites. What that means is that they start life as males, but under certain circumstances become females. Typically an adult pair—a female and a male—and between two and four smaller fish live together in a single anemone. The dominant, largest fish is generally a female. She possesses functioning ovaries and degenerate testicular tissue. The next-largest fish has functioning testes as well as some latent ovarian cells. If the dominant female dies, her mate’s gonads cease to function as testes and the egg-producing cells become active. Simultaneously, the largest of the nonbreeding individuals becomes the functioning male.
So, had Marlin, Nemo’s dad, just hung around for a while, he would have become a she and Nemo would have had his mom back. Then, with time, Nemo himself would have matured into a functional male, and . . . but perhaps that’s all a bit too dark for the story line.
My second thought as an ichthyologist is, What species is Nemo? According to the UNEP-WCMC report, A. ocellaris is the second most commonly imported marine ornamental fish species worldwide. Its close cousin A. percula, however, is the clownfish more commonly imported into the United States. Both species look very much like Nemo—though I’d say A. ocellaris is closer to what the artists at Pixar Animation Studios were drawing. The species are almost identical, except for some minor color differences and the fact that A. ocellaris usually has eleven spines on its dorsal fin, whereas A. percula has ten.
But here’s the clincher: The range of A. ocellaris extends into the Indian Ocean from the coast of northwestern Australia, whereas A. percula is from the western Pacific and occurs on Australia’s Great Barrier Reef. But in the story, Nemo’s dad Marlin hitches a ride on the East Australian Current to get himself to Sydney. Because the current moves eastward he would pretty much have had to live somewhere in the western Pacific, probably on the northern Great Barrier Reef. That makes Nemo A. percula, the orange clownfish, no question. And to think anyone ever told me that my studies of fish taxonomy would never get me anywhere.
In spite of the bleaker aspects of the marine-aquarium trade, there is plenty of reason for optimism. Animals taken from reefs for aquariums are among the reef habitat’s most valuable products. A pound of fishes harvested from the reefs of the western Indian Ocean and sold for aquariums earns more than $200 for the local fishermen; the same pound sold for food would yield them less than $3. Similarly, live coral earns some $6,300 per ton for the gatherer, whereas the same ton of coral taken for limestone fill—often extracted with dynamite—sells for around $50. Hence market forces could provide a strong financial incentive for both subsistence harvesters and local authorities to maintain and protect their reefs.
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Such a program offers hope that harvesting reefs need not obliterate them. To be effective in the long term, however, the programs will demand vigilance and commitment by the governments of the source countries as well as by the governments of the importing countries. Governments and non-governmental organizations can work together to implement export quotas and permits, establish marine reserves, and temporarily close critical areas to help promote sustainable practices.
| Groups concerned with the fate of dolphins, and of tuna, cod, salmon, sturgeon, and other food fishes, have long advocated such a strategy. Similar consumer-based approaches are being developed to encourage best practices in the harvesting, holding, packaging, and transportation of animals for the aquarium trade. |
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The scientific study of reef organisms and their role in a functioning ecosystem is another obvious course to pursue. Data gathered on the suitability and resilience of various organisms to harvesting, on their life histories, and on their adaptability to life in aquariums will be needed to make sound decisions. More data may also help investigators develop techniques for raising marine animals in captivity, thereby reducing the pressures of harvesting on their counterparts in the wild.
But perhaps the best approach to saving Nemo is the one based on the simple idea that an educated and concerned body of consumers can have a major impact on how the industry supplies the organisms the public demands. Groups concerned with the fate of dolphins, and of tuna, cod, salmon, sturgeon, and other food fishes, have long advocated such a strategy. Similar consumer-based approaches are being developed to encourage best practices in the harvesting, holding, packaging, and transportation of animals for the aquarium trade. The Marine Aquarium Council (MAC), for instance, seeks to create standards and certify sustainable practices for the trade; the council’s strategy is then to stimulate consumer demand for the certified products. A list of the companies now seeking certification, or which already sell MAC-certified marine animals, can be found at www.aquariumcouncil.org.
Whenever you or I enter a restaurant or a supermarket, we have innumerable choices about the seafood we buy. In making our choices, we vote with the pocketbook, and that vote carries enormous weight with producers. We have the power essentially to force producers to minimize environmental costs—for unless they do, we will buy elsewhere. If the real cost, for instance, of gorging on “all you can eat” seafood buffets were part of the advertising campaign, I doubt we would find the menu so appetizing.
The same is true when we choose our aquarium pets. Guillaume Rondelet might have had some idea that he was initiating a new science when he wrote his book on marine life. But Mme Rondelet, who would never have guessed that fishes might someday be endangered, could never have known that she might be taking the first step toward saving fishes when she kept one of them in a jar.
Melanie L. J. Stiassny has spent the past twenty-five years studying the evolution and behavior of tropical fishes and looking for ways to safeguard them and their habitats. She is the Axelrod Research Curator in the American Museum of Natural History’s Department of Ichthyology, an adjunct professor at Columbia University, and served as the head curator for AMNH’s renovated Hall of Ocean Life. High on her recommended reading list, she says, is One Fish, Two Fish, Crawfish, Bluefish: The Smithsonian Sustainable Seafood Cookbook, by Carole C. Baldwin and Julie H. Mounts (Smithsonian Institution Press, 2003), followed by Song for the Blue Ocean, by Carl Safina (Henry Holt and Co., 1998).
Copyright © Natural History Magazine, Inc., 2004