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Coastal Heritage Magazine

Shrimp Aquaculture: Challenges and Potential

Booming global trade enables animal viruses to race around the world. Now aquatic farmers and researchers are finding new strategies to contain them.

High Security. The next major step in shrimp-farming technology could be the “biosecure” greenhouse, says Jeff Bruce, wildlife biologist at the S.C. Dept. of Natural Resources Waddell Mariculture Center. By raising shrimp in enclosed greenhouses with recirculating water, farmers could keep out animals that can carry pathogens into farm ponds. Photo by Wade Spees.

Shrimp Aquaculture: Challenges and Potential

Until a few decades ago, peasants cultivating family or communal ponds grew nearly all of the world’s farm-raised fish and shellfish. Farmers in poor countries, particularly in Asia, used ancient techniques to raise modest harvests of carp or shrimp, which they consumed or sold to neighbors and nearby markets.

By contrast, farmers who raised beef, chicken, and sheep have been an important cog in industrial economies for a long time. In the mid-nineteenth century, American investors built sophisticated networks of railways, stockyards, slaughterhouses, and processing plants to deliver livestock from the Great Plains and the rural Midwest to urbanites hungry for meat. As animals were crowded into tighter and tighter quarters for greater efficiency, livestock diseases had more opportunity to spread rapidly. But by then, scientists had made progress in identifying livestock pathogens and setting up quarantines to prevent and control epidemics.

When aquaculture suddenly modernized in the late twentieth century, it faced similar challenges. Aquaculture is now the fastest growing food-production system in the world. And just three decades from now, aquatic farming could provide the largest source of fish and shellfish for human consumption. Yet while aquaculture has grown swiftly, it has also experienced growing pains, including devastating infectious diseases.

Aquaculture’s revolution began during the 1970s, when the World Bank and international aid organizations became concerned about a deepening hunger problem in poor countries. As human populations skyrocketed, experts worried that hundreds of millions of people would suffer malnutrition. So international agencies began aggressively promoting aquaculture in developing countries as a way to provide a crucial source of animal protein and nutrients for the poor and to promote economic development.

On the Cover. Giant “specific-pathogen-free” broodstock shrimp are kept in contained systems at Atlantic Farms on James Island. These shrimp have undergone rigorous testing for viruses and other pathogens, and their offspring are sold to farmers in South Carolina and around the world. Photo by Wade Spees.

During the last quarter of the twentieth century, worldwide population ballooned from four billion to six billion, and most of this growth occurred in the developing world. In the same period, wild fish harvests leveled off, reaching a plateau in the 1990s. Now about three-quarters of the major marine fish stocks are harvested at least to their maximum limits, according to The State of World Fisheries and Aquaculture 2000, a report by the United Nations Food and Agriculture Organization (FAO). There is little or no room for growth in international wild harvests, experts say.

So where can we find more fish to feed the world? Aquaculture will provide most of it, experts say. From 1984 to 1999, aquaculture production expanded from 7 million to 33 million metric tons. Today, aquaculturists provide one-third of the Earth’s total food fish supply.

But along with this remarkable worldwide growth has emerged problems of success, particularly catastrophic animal diseases. Since its beginnings 25 years ago, for example, high-production shrimp farming has been a boom-and-bust phenomenon. Nearly all of the farmed shrimp in the world is grown in South American and Asian countries, such as Taiwan, Thailand, Indonesia, and Ecuador. Yet virtually every country with a major shrimp-farming industry in the 1980s and early ‘90s suffered viral epidemics, which do not affect human health, and production crashes. In Asia alone, shrimp viruses cost farmers about $1 billion a year since 1994.

Making a Splash. To increase production, shrimp farmers use paddlewheels that improve water quality by mixing pond water and raising dissolved oxygen levels in ponds. Photo by Wade Spees.

In the 1980s and early ‘90s, a small band of South Carolina shrimp farmers started building a domestic industry. They were encouraged by the pioneering work of the S.C. Department of Natural Resources (DNR) Waddell Mariculture Center and shrimp-aquaculture research funded by the U.S. Department of Aquaculture’s U.S. Marine Shrimp Farming Program and the S.C. Sea Grant Consortium.

But in the mid-‘90s, the South Carolina industry became a victim of virus epidemics incubated in poorly sited and managed ponds overseas. Global trade allowed virulent animal viruses to move from country to country, continent to continent, until they reached here.

In recent years, lowcountry shrimp farming took a severe pounding. Seventeen local farms, with a total of 262 acres, produced more than a million pounds of shrimp in 1994. Five years later, there were only 10 local farms, with a total of 62 acres, producing 154,000 pounds. Partly due to virus problems, the U.S. shrimp farming industry has remained tiny. A 1998 survey showed that only 20 U.S. farms were in operation, with an estimated 400 hectares (988 acres) in growout ponds, located in South Carolina and Texas.

Recently, however, lowcountry shrimp farming has made a modest comeback, with the largest farm in South Carolina stocking shrimp again for the first time in two years.

Global Markets

Shrimp aquaculture for international export markets is only a few decades old. During the late 1960s and early 1970s, researchers in Taiwan, China, France, and the United States began exploring the potential of shrimp farming, all searching for better methods of breeding and raising crustaceans in ponds, while struggling with issues of nutrition and disease.

In the United States, the National Sea Grant College Program supported research on shrimp aquaculture technologies at coastal universities. Investors learned about these new technologies and traveled to Latin America, setting up shrimp farms, hatcheries, feed mills, and seafood processing plants. In the late 1970s, Ecuador became the first country in Latin America to build a major shrimp-farming industry, selling their product primarily to the United States.

The first Asian boom arrived in Taiwan, also during the late 1970s, when farmers learned how to grow large numbers of shrimp in small ponds, and distributors sold the product for a premium in the international marketplace, particularly to Japan. Suddenly dozens of Taiwanese farmers became millionaires.

Word quickly spread to other countries about fabulous profits available in shrimp. In the 1980s, China, Thailand, Indonesia, and the Philippines became leaders in cultured production. In southern Thailand during the 1980s, “shrimp farming was a gift from the heavens,” even for landowners with only enough space to build a single pond, writes anthropologist Mike Polioudakis in World Shrimp Farming 2000, an industry overview. “Some went from subsistence farmers to car ownership to private schools for their children in less than one year.”

Pick of the Litter. These juvenile shrimp at the Waddell Mariculture Center are part of an ongoing study of animals grown in greenhouses. The shrimp are routinely sampled and examined for health and growth. Some researchers believe that raising shrimp in enclosed environments with recirculating water could be an answer to future viral threats. Farmers could use greenhouses to grow shrimp anywhere in South Carolina. Photo by Wade Spees.

Few people in Illinois or Kentucky or even upstate South Carolina regularly ate shrimp 25 years ago. It was considered a luxury seafood, enjoyed on rare vacations to the coast. But dietary patterns began changing when seafood distributors marketed frozen shrimp around the nation. Grocery stores opened special seafood displays and counters; chain restaurants advertised shrimp dishes. Some health-conscious Americans shifted from eating beef to fish and shellfish. The international hit movie “Forrest Gump,” featuring a holy fool who became a trawl shrimper, also boosted sales. The U.S. has a larger trade deficit in shrimp than in any other product but one: petroleum.

New global markets for shrimp helped spawn “an economic revolution in all fish trade,” a $53 billion industry, says Christopher Delgado, senior research fellow at the International Food Policy Research Institute. In value terms, shrimp is the primary fish commodity sold worldwide—worth an amazing one-fifth of the total value of internationally traded fish products. “Fifteen years ago,” says Delgado, “fish was a major product of the North, essentially shipped south.” Now it’s the other way around. Poorer countries in the Southern Hemisphere are the primary producers, catching and farming seafood to send to richer nations in the Northern Hemisphere, Delgado points out. “The total value of net fish exports from developing countries to developed countries is overwhelmingly products like shrimp and is more important in value than coffee, tea, cocoa, sugar, and bananas combined.”

Sign of the Times. This sign at the Waddell Mariculture Center in Beaufort County reflects growing concern about shrimp viruses slipping into research facilities and farms. Photo by Wade Spees.

For certain developing countries, shrimp farming, like international tourism, offers needed foreign currency and jobs. Indonesia’s shrimp-aquaculture industry, for example, provides 150,000 jobs in production, processing, transportation, marketing, and related service activities; Ecuador’s farms generate 160,000 direct and indirect jobs.

Spreading Viruses

In the ocean or estuary, shrimp carry viruses that usually do not affect their health. But when a farmer in Asia or South America takes post-larval shrimp—generally a few weeks old after hatching— from the wild and grows them in a densely crowded pond, the shrimp can become stressed and vulnerable to latent viruses. Or when an overseas farm draws in untreated and unfiltered water laden with tiny wild shrimp infected by viruses, the pond shrimp can get infected too. As ill shrimp die, they are cannibalized by healthy ones, spreading disease among the pond’s population.

Lured by high profits, overseas farmers converted coastlines into shrimp operations during the 1980s and early ‘90s. To reduce stress on their aquaculture stocks, overseas farmers would routinely release about 20 percent of each pond’s water into estuaries. In some cases, viruses were allowed to escape. Then neighboring aquaculturists pumped in untreated water from the same source. Thus pond conditions deteriorated, and viruses spread swiftly from farm to farm. Birds also ate infected shrimp in a pond and later defecated the virus into another pond miles away; the disease leapfrogged along coastlines. Suddenly, epidemics raced around the world in broodstock, post-larval shrimp, and food shrimp.

Plush Accommodations. South Carolina’s farmers have implemented a number of management improvements since the viral outbreaks of the 1990s, says Al Stokes, facility manager at the Waddell Mariculture Center in Beaufort County. Farmers have lessened animal crowding in ponds and decreased the amount of water pumped in and out of farms. They installed finer mesh screen in water pipes, reducing the chance of introducing pathogens, predators, and competitors. They also double-screened discharge pipes to prevent releases of farm shrimp to the wild. Photo by Wade Spees.

“When you increase the intensity of production, you generally increase the potential for catastrophic diseases,” says Jack Whetstone, aquaculture specialist with the S.C. Sea Grant Extension Program.

As international trade spreads into every corner of the world, catastrophic livestock diseases have become headline news. In March 2001, for example, U.S. officials banned imports of animals and animal products from Europe after learning that foot-and-mouth disease had spread from Britain to France. This highly contagious virus, which affects cattle, sheep, pigs, and other cloven-footed animals, has been reported in Argentina and Uruguay. Although posing no threat to human health, the virus could cost American farmers billions of dollars if it arrives here.

Shrimp viruses are a similar concern, says George Chamberlain, president of the Global Aquaculture Alliance, an industry group. Shrimp farmers overseas paid scant attention to potential diseases until the virus catastrophes of the early ‘90s, he points out. “It’s hard to imagine sending chicken or pigs around the world with no biosecurity measures” to control the spread of infectious diseases. Biosecurity measures include quarantine procedures for broodstock, sanitary disposal of dead animals, and establishment of certification programs for disease-diagnosis laboratories.

“Diseases are part of the regular growth of a livestock industry,” says Whetstone. “We should’ve better anticipated the virus problems in shrimp aquaculture,” though some U.S. farmers and researchers were aware of the catastrophic disease threat and were working to address it.

Disease outbreaks are a symptom of larger issues, says Jason W. Clay, aquaculture expert with the World Wildlife Fund. To cope with potential diseases, overseas farmers used certain management techniques that harmed coastal water quality. That is, many overseas farmers attempted to reduce stress on their pond animals by releasing large amounts of nutrient-rich wastewater into estuaries, contributing to algal blooms under certain conditions.

Farmed salmon and other finfish have also been plagued by disease. “As aquaculture enterprises intensify, and farmers try to produce more on the existing resource, one of the first major problems to arise is fish disease,” says Meryl Williams, director general of the International Center for Living Aquatic Resources Management (ICLARM), headquartered in Malaysia. “We’ll continue to see enormous problems with fish disease in the future.”

Most observers agree that shrimp farming causes few, if any, impacts when properly conducted. To improve their environmental record, well-capitalized overseas shrimp farms, especially in Asia, have already changed how they grow crustaceans. “Large farmers have better access to (technical experts) who can teach them,” says Clay. “Many of the poorer farmers do the most damage (to the environment) and have the least information available to improve their practices.”

Conservation groups have sharply criticized Asian and Latin American operations, which produce nearly all of the farmed shrimp worldwide. Recently, environmental groups also stepped up criticism of the domestic industry, calling for tighter state and federal regulations.

South Carolina farmers say they are unfairly tarred by overseas blunders. “U.S. aquaculture is taking a bad rap,” says Rick Eager, his voice rising in frustration. Owner of Swimming Rock Fish & Shrimp Farm near Meggett and president of both the S.C. Aquaculture Association and the S.C. Shrimp Growers Association, Eager points out that aquaculture does vastly more good than harm and that fish and shellfish farming in the United States, by and large, is an environmentally responsible industry.

“It’s guilt by association,” says Eager, who lost a crop to taura syndrome virus in 1996 and now grows native shrimp for local bait markets. “Some of the Third World countries have poor environmental records. But U.S.—and particularly South Carolina—aquaculture is already tightly watched and regulated.” American shrimp farming does not need further regulation, he says.

Domestic shrimp farmers have worked hard to develop “green” businesses here. They run cleaner, more sophisticated operations than many overseas. Even so, U.S. aquaculturists must still confront potential epidemics plaguing other parts of the world. To address the problem, U.S. farmers and researchers continue refining biosecurity systems and best management practices in shrimp aquaculture.

Industry Reforms

Shrimp aquaculture grew too quickly in some developing countries, most observers agree. In the boom years, governments were so eager to encourage lucrative shrimp farms that they failed to establish or enforce coastal environmental protections. Certain sectors have been “driven mainly by market forces, short-term profits, and in many developing countries, export earnings,” says Meryl Williams. “We’ve tended to muddle through,” she adds. “Present aquaculture practices are far from ideal. Aquaculture is an industry that the world needs, but we’ve certainly got to get it right.”

Despite urgent needs for reform, most nations still have not established policies and regulations that address how shrimp farms should be installed and operated, according to a 1999 report by the Global Aquaculture Alliance. The report points out that “it will be many years before most nations will be able to formulate and enforce reasonable regulations for shrimp farming.”

The situation is changing for the better, however, as some countries tighten environmental laws in coastal areas. Recent epidemics, moreover, have prompted sophisticated farmers to re-evaluate how they do business. Many farmers recognize that they need better husbandry methods to reduce pathogen risks. Now the Global Aquaculture Alliance is encouraging voluntary reforms of shrimp farming practices through “codes of practice.” Aquaculture associations in some major shrimp farming nations, including Thailand and Eduador, are adopting environmentally friendly codes of conduct.

South Carolina shrimp aquaculturists have implemented a number of management improvements since last decade’s outbreaks to address diseases coming from outside the farms. They lessened animal crowding in ponds and decreased the amount of water pumped in and out of farms. They also installed finer mesh screen in water pipes, reducing the chance of introducing pathogens, predators, and competitors. They also double-screened discharge pipes to prevent releases of farm shrimp to the wild.

In South Carolina, DNR has designed strict permitting guidelines for non-native shrimp culture. Farmers must submit extensive operations plans and follow tougher rules for testing, confinement, and destruction of animals if a virus is found. And local farmers must buy virus-free young shrimp only from hatcheries that undergo rigorous testing, according to the standards established by the U.S. Marine Shrimp Farming Program.

State and federal grants have helped support a hatchery at Atlantic Farms on James Island, which produces virus-free young shrimp for area growers. “If your broodstock is free of any diseases, and you have diseasefree offspring, then you have your best shot at resisting diseases,” says Knox Grant, manager of Atlantic Farms.

The tougher permit requirements and the local hatchery have been successful, so far. The state’s farms were virus-free in 1999 and 2000. Now U.S. shrimp farms are under the strictest regulatory structures in the world, says Eager.

Bone Dry. South Carolina shrimp farmers allow their ponds to dry out during the winter months. Sunlight oxidizes and removes organic material and fecal matter that build up on the pond bottom. The dark, cracked layer shown on this pond bottom is dried algae. Photo by Wade Spees.

But epidemics remain a threat. “When some overseas shrimp farmers find a disease in their ponds, they immediately harvest their shrimp,” says Dale Theiling, assistant director of the DNR Office of Fisheries Management. “That way they can get a product out of their ponds, even if it’s a smaller size. These shrimp go on the market, and wherever the shrimp go, the virus goes.”

Virtually all shrimp imported to the United States is funneled through giant distributing companies that handle both wild-harvested and farm-raised crustaceans from around the world. Distributors freeze the animals and sell them to grocery stores and restaurants and fishing docks, where small shrimp are used for bait.

“We know there are thousands and thousands of pounds of shrimp being imported (as food for humans or for bait),” says Theiling, “and much of this shrimp is known to be infected with a virus. But (DNR officials) have no control over imports of food shrimp. A lot of these smaller shrimp are sold at shrimp docks or other facilities, where people may ‘head’ their shrimp, and the heads go into our native waters, potentially introducing the disease (to local wild stocks).”

From wild stocks, a virus can slip into shrimp ponds, and then it can spread rapidly to nearby farms, starting an epidemic on the farms.

The Future

U.S. shrimp farmers face challenging years ahead. “This is a very difficult period,” says Whetstone. The overseas disease threat is probably not going away. Aquaculturists have difficulty raising enough money to invest in new equipment because many lenders and investors are wary of the industry’s potential risks. Standard federal crop insurance does not cover most forms of aquaculture. And investors get scared away from marine aquaculture by coastal property’s high cost. After farmers have spent money on coastal land to start a shrimp operation, they’ve used up a lot of their capital. Moreover, as property values rise on the coast, so do taxes. Some farmers could be forced to choose between growing shrimp or selling off their land to developers.

Growing shrimp and other marine foods in the United States is costlier than in developing nations. Labor and waterfront land are far more expensive here. Moreover, lowcountry farmers compete with overseas aquaculturists who comply with less stringent permits and less costly regulations in their countries.

Even so, U.S. regulations could get even tighter. Because of their small size, most South Carolina shrimp farms qualify for an exemption from Clean Water Act rules on wastewater discharges into waterways. South Carolina shrimp farmers say that their discharges have no environmental impacts. But under a consent order by a federal court, the U.S. Environmental Protection Agency, concerned about potential nutrient pollution, is considering tougher minimum standards on discharges by many industries, including aquaculture.

The agency is gathering information on discharges from various kinds of aquaculture production systems and 13 cultured species, according to Marta Jordan, EPA engineer and project manager. If EPA decides to regulate certain production systems or species, the agency could require some farmers to upgrade their water-treatment facilities. This would be cost-prohibitive for farmers, local aquaculturists say. Or EPA could demand more rigorous management practices, such as requiring farmers to hold wastewater in settling ponds before discharging it. U.S. farmers might have to spend money to retrofit aquaculture ponds or build new ones as waste-settling ponds. Another option for EPA is to make no new regulations on aquatic farming. The proposed rule is due in June 2002, and the final rule two years later.

Local Angle. Always purchase South Carolina native shrimp—frozen or live—for fish bait. Food shrimp from grocery stores is likely imported and could be infected with viruses, which do not affect human health but could affect local wild shrimp. Photo by Wade Spees.

Farmers hope that EPA will choose the “nochange” option. “Aquaculturists feel that they are environmental stewards,” says Betsy Hart, National Aquaculture Association executive director. “There is not a defined and proven (water quality) problem from aquaculture, and therefore we question why EPA is developing minimum standards.”

Shrimp farmers say that their discharges consist mainly of live algae that do not harm local waters. New regulations, Eager says, are unnecessary and costly, potentially putting most South Carolina shrimp farmers out of business. If such rules were mandated, locally grown virus-free shrimp would likely be “replaced by foreign virus-infected shrimp,” he says.

There is good news on the horizon for local shrimp farmers, though. Scientists are constantly experimenting with new technologies to make domestic shrimp aquaculture more feasible. Researchers continue efforts to improve disease-free broodstocks through the U.S. Marine Shrimp Farming Program. They are experimenting with greenhouse systems where crustaceans can be grown year-round, even in South Carolina’s relatively cool climate. With support from the S.C. Sea Grant Consortium and the U.S. Dept. of Agriculture, South Carolina researchers have helped develop and refine techniques to keep water almost exclusively within farms, with no discharges and little water pumped in. This is called “closing” the system. Many Asian farmers have “learned to avoid losses from disease by greatly reducing water use,” says Chamberlain. “It’s too much of a (disease) risk to exchange water” with outside resources.

So far, however, local shrimp farmers don’t use closed systems. It’s expensive and technologically difficult to sustain a crowded but healthy shrimp population in a closed system. “You have to prove a technology works over time,” says Whetstone, “and then you have to prove it works economically before people are going to jump into it.” But soon there could be new tools, species, products, and markets to develop a significant U.S. shrimp aquaculture industry. For example, aquaculturists are growing shrimp in low-salinity aquifer-fed inland ponds in West Texas, Arizona, and Alabama.

Moreover, each terrestrial livestock industry—cattle, chicken, and sheep—has continued to face major disease challenges. But researchers at land-grant universities have gained greater understanding of various pathogens, and agricultural extension specialists have worked with farmers on better management techniques to control diseases. For more than two decades, Sea Grant scientists and extension specialists have followed this same path of research and outreach on various cultured fish and shellfish species.

Now both domestic and international shrimp farming are poised for a period of vigorous growth, according to hatchery manager Knox Grant, who recently sold post-larvae to farmers in South Carolina, Israel, and Alabama. He hopes to sell to growers in Arizona, Italy, and Japan. “I get calls every two weeks,” he says, “from people who’ve got shrimp fever.”

Sidebar

Seafood Alliance

South Carolina’s fish farmers and commercial fishermen are teaming up with representatives of the food and beverage industries to market the state’s seafood.

Members of the new S.C. Seafood Alliance include “anybody who has anything to do with seafood from the time it’s harvested until it’s on the dinner plate,” says Darlene Dopson, the group’s acting executive director.

The alliance fills a need for cooperation among various sectors of the seafood industry, she says. “We’re the only (coastal) state that doesn’t have a marketing program for its seafood products.”

It hasn’t been easy bringing all the disparate interests together, says Dopson, whose husband and father are Beaufort County shrimpers. The alliance includes crabbers, fishermen, shrimpers, oystermen and others who harvest shellfish, restauranteurs, seafood packers, distributors, and aquaculturists.

“Uniting the seafood industry is the biggest challenge,” Dopson says. “But people in various industry sectors are recognizing that they need a common vehicle to market South Carolina seafood. They recognize they have many of the same problems, and similar regulation, management, and resource issues.”

International seafood industry groups are trying to move in the same direction. Consumers don’t differentiate between farm-raised and wildcaught seafood, notes George Chamberlain in a recent issue of Global Aquaculture Advocate, a trade magazine. The alliance is working to build relationships with fisheries organizations worldwide. “When one portion of the seafood industry is attacked, the entire industry suffers, and when one is praised, we all benefit.”

Sidebar

Fish as Food for Fish

The growing demand for farm-raised shrimp, salmon, trout, and other species fed high-protein diets could harm wild fish stocks, according to an article published in June 29, 2000 issue of scientific journal Nature.

The rapid rise in aquaculture production “is a mixed blessing . . . for the sustainability of ocean fisheries,” writes a team of scientists and economists. Overall, aquaculture production adds to world fish supplies, the authors say. But aquaculture operations that raise these species are indirectly threatening biologically important wild fish populations.

To grow species quickly and to enhance their flavor, farmers use processed food—fishmeal and oil—made from small, pelagic species harvested from the ocean, including menhaden from the Gulf of Mexico, Peruvian anchovies, Icelandic herring, Norwegian capelin, and sand eels from the North Sea.

It takes about three pounds of processed wild-caught fish to grow one pound of salmon or marine shrimp, according to the Nature authors, though other researchers argue that these numbers are outdated. In 1999, it took 2.73 pounds of pelagic fish to grow one pound of salmon, and about 2.08 pounds of pelagic fish to grow one pound of shrimp, according to Albert Tacon, aquaculture nutritionist based in Hawaii. In any case, harvesting huge amounts of small forage fishes to feed cultured species disrupts marine food chains, according to the Nature article. About one-third of the annual global wild fish harvest is used as food for various forms of livestock, including poultry and cultured fish and shellfish.

But the fish-feed controversy is overblown, say some aquaculture experts. Four countries produce most of the fish used in fishmeal and oil worldwide: Peru, Chile, Iceland, and Denmark. Forage-fish stocks rise and fall dramatically from year to year. There are severe fluctuations in harvests during El Nino years, which disrupt fish populations offshore from Peru and northern Chile. But these nations have strict regulations to ensure that fish populations are not over-harvested, according to Ronald Hardy, director of the Hagerman Fish Culture Experiment Station at the University of Idaho.

The world’s poultry growers use the largest proportion of fishmeal, though they have scaled back due to its high cost over the past decade. Aquaculture producers meanwhile have picked up the slack. If aquaculturists didn’t buy fishmeal, then poultry producers would purchase more of it, Hardy says.

The vast majority of animals grown on fish farms—carps, catfish, tilapia, and milkfish—live on diets consisting primarily of plant food and minimal amounts of fishmeal. Filter feeders, such as clams, scallops, oysters, and some kinds of carp, do not directly consume fishmeal in their diets. But carnivorous fish and shellfish require high-quality protein in their diet, which is supplied by top-grade fishmeal.

Both sides agree that it’s a good idea to reduce dependence on fish products to grow carnivorous animals. There are limited supplies of pelagic fish, so researchers are seeking substitutes for high-quality protein in vegetable and grain products. “If you want this (aquaculture) sector (of marine shrimp and salmonids) to keep growing, you have to base that growth on ingredients that can keep pace,” such as vegetables and grains, says Tacon.

Sidebar

Aquaculture Systems

There are three basic systems used in shrimp aquaculture.

In the first system, traditional farmers use a variety of techniques collectively called “extensive aquaculture.” On extensive shrimp farms, aquaculturists allow wild post-larval shrimp to flow with tides through open gates into low-lying manmade impoundments along bays or tidal rivers. Then farmers close gates, trapping young shrimp within the ponds before the tides go out. Although these farmers don’t directly feed their stock, some do add organic or inorganic fertilizers to stimulate growth of algae and other organisms, which the crustaceans feed on. Stocking densities are generally low. For shrimp, extensive farmers stock about 25,000 postlarve (or young shrimp) per hectare (a metric unit of area equal to 2.471 acres).

The second type of aquaculture system is called “semi-intensive,” in which farmers add feed for captive animals. In semi-intensive shrimp farms, built above the high-tide line, farmers crowd animals together in moderate densities—100,000 to 300,000 postlarve per hectare.

The third kind of system, “intensive,” provides all nutritional requirements for farmed shrimp. On intensive shrimp farms, the ponds are small, constantly managed, with heavy feeding and high densities—more than 300,000 postlarve per hectare. Farmers aerate ponds with paddlewheels or other tools to add oxygen to the water. Most U.S. shrimp farms are intensive systems due to the high cost of coastal land.

Sidebar

Asian Aquaculture

Aquaculture has flourished in China for three thousand years, but just during the past 20 years Chinese aquaculture has seen unprecedented success with freshwater fish production in inland ponds and lakes.

“China is big, and it’s hungry,” says Albert Tacon, aquaculture nutritionist based in Hawaii.

China’s aquaculture industry began to develop steadily from the 1950s through the 1970s, when researchers learned how to inject fish with massive amounts of hormones to make them spawn. Government hatcheries and nurseries produced large numbers of fingerlings, or young fish, but there weren’t enough farmers to grow them.

In the late 1970s, China began to encourage entrepreneurs, and soon families started small fish farms in back yard ponds. Since the early 1980s, China’s production has grown by more than 16 percent per year. Meanwhile, freshwater finfish farming has also boomed throughout Southeast Asia.

Asian farmers have improved fish nutrition through modern pelleted feeds rather than by digging huge numbers of new ponds. In a traditional fishpond enriched by manure and grass, a farmer could annually harvest 300 to 500 kilograms of fish per hectare, according to Ronald Hardy, aquaculture nutritionist at the University of Idaho. But Asian farmers have recently begun feeding their carps with modern feeds, made up of soybeans and small percentages of fish meal, resulting in 10-fold harvest increases.

Further Reading

Boyd, Claude E. et al. “Codes of Conduct for Marine Shrimp Aquaculture.” In The New Wave, Proceedings of the Special Session on Sustainable Shrimp Culture, Aquaculture 2001. Baton Rouge, La.: World Aquaculture Society.

Boyd, Claude E. Codes of Practice for Responsible Shrimp Farming. St. Louis: Global Aquaculture Alliance, 1999.

Chamberlain, George. “The Dream of a United Seafood Industry.” Global Aquaculture Advocate, Feb., 2001.

Goldburg, Rebecca and Tracy Triplett. Murky Waters: Environmental Effects of Aquaculture in the United States. Washington, D.C.: Environmental Defense Fund, 1997.

Lindbergh, Jon. “Salmon Farming in Chile: Do the Benefits Exceed the Costs?” Aquaculture Magazine, March/ April, 1999.

Moss, Shaun M. “Greening of the Blue Revolution: Effor ts toward Environmentally Responsible Shrimp Culture.” In The New Wave, Proceedings of the Special Session on Sustainable Shrimp Culture, Aquaculture 2001. Baton Rouge, La.: World Aquaculture Society.

Naylor, Rosamond L. et al. “Effect of Aquaculture on World Fish Supplies.” Nature, June 29, 2000.

The State of World Fisheries and Aquaculture 2000. Rome: United Nations Food and Agriculture Organization.

World Shrimp Farming 2000. Bob Rosenberry, Ed. San Diego: Shrimp News International.