The International Aquaculture Market and Global Needs
Author’s present address: AcuaBiotec LLC, 10400 Windfall Court, Damascus Maryland 20872 USA
Aquaculture production is meeting a rising demand for a variety of fishery products, including fish, shrimp, shellfish, and aquatic plants. The capture fishery for seafood used for human consumption has remained stable at about 60 million metric tons per year from 1984 to 1996. However, aquaculture production has increased from about 13 to over 35 percent of the capture fishery yield over the same period, exceeding 20 million metric tons per year in 1996 (Figure 10–1) (Tacon, 1998a,b; New, 1997). During this time, major commercial fishing grounds have been classified as “fully exploited” or “over exploited.” The Food and Agriculture Organization (FAO) estimates world annual consumption of seafood in year 2010 to be 110 to 120 million metric tons with an estimated supply of 74 to 114 million metric tons. A likely scenario to expect by the year 2010 will be a deficit of 36 million to 46 million metric tons of seafood for human consumption (Food and Agriculture Organization, 1996). With capture fisheries seemingly limited to 60 million metric tons per year, aquaculture production must double over the next 15 years simply to keep
up with expected population growth at today’s per capita seafood consumption. Over 120 species of fish are farmed throughout the world, and the diversity of species is nearly matched by the diversity of farming practices used to produce them.
OVERVIEW OF WORLD FISH PRODUCTION
The majority (nearly 90 percent) of fish production from aquafarms occurs in Asia, especially China. China is the only country where aquaculture supplies food for more people than does the country’s capture fishery industry. In 1978, China produced less than 1 million metric tons of fish through aquaculture and 2.5 million metric tons through its capture fishery industry. But in 1997, China produced 20 million metric tons of fish from aquaculture and 15.7 from capture fishery (Fish Farming International, 1998).
China raises a great variety of aquatic animals for human consumption ranging from turtles to crabs to eels. However, production of cyprinids, carp, and related freshwater fish species, which are an important and inexpensive protein source consumed internally, comprise the greatest aquaculture crop in the
world (Tacon, 1998a,b; New, 1997). At approximately 10 million metric tons and $10 billion dollars in value, cyprinid production, accounts for about 76 percent of the world’s total aquaculture production tonnage and 46 percent of the world’s aquaculture crop value. At about 0.5 million metric tons and approximately $3.5 billion in value, tiger prawn—the most popular shrimp species grown in Asia—accounts for about 4 percent of the world’s tonnage and over 16 percent of the world crop value.
Salmon farming has become a major industry in Norway, Scotland, Chile, and Canada, and today, over 70 percent of the salmon consumed in the world comes from salmon farming, rather than from capture fisheries. Salmon production tonnage is similar to that of tiger prawn and tilapia and ranks third in terms of value at approximately $1.8 billion. The top species grown in aquaculture and their market value are represented in Figure 10-2 (Tacon, 1998a).
Shrimp farming supplies about one quarter to one third of the world’s consumption and is a major source of foreign exchange for many developing countries, with Thailand and Ecuador as number one and two shrimp-producing countries over the last decade, respectively. About 80 percent of the world’s farmed shrimp is produced in Asia, and the remainder is produced primarily in Latin America. The United States and Japan are the world’s largest importers of shrimp. Farmed shrimp production has a world trade value estimated at about $6 billion from about 814,000 metric tons of live weight produced in 1999 (Rosenberry, 1999). This represents an increase of about 10.4 percent over 1998 production. The increase came from Asia, as the major producing countries in Latin America suffered severe losses to diseases in 1999, and these losses continued in 2000.
The most destructive diseases have affected the world’s shrimp farming industry for over a decade, with the first massive losses experienced in Taiwan in 1987-88 and then continuing through Asia in the 1990s and crippling the West in the last two years. These severe epizootics include several different viruses, which appear to cause the most damage when they occur in combination with pathogenic Vibrio bacteria. Estimates of some of the losses and economic damage caused by major epizootics are presented in Table 10-1 and losses realized by Thailand and Ecuador are presented in Figure 10-3.
TABLE 10-1. Some estimated losses to disease in world shrimp farming.
Application of chemicals and antibiotics to aquatic feeds and water are the most commonly used methods to fight diseases, especially in shrimp farming. In fish such as salmonids, which have a specific immune system, vaccines can be used to prevent disease. However, shrimp do not have a specific immune system, and the widespread use of chemicals and antibiotics, which are ineffective in fighting viral diseases, are harmful in the long term. Strong microbiologic evidence indicates that with the use of antibiotics and chemicals, bacterial pathogens that cause disease in humans, such as Vibrio cholerae, have evolved (horizontal gene transfer) to more harmful and more resistant types (De La Cruz and Davis, 2000; Rowe-Magnus and Mazel, 1999). By implication we can surmise that the same has occurred in aquaculture; in regions where antibiotic use has been heavy, bacterial pathogens now cause greater rates of shrimp mortality than in previous years (Moriarty, 2000). Continued use of antibiotics and chemicals in open systems can cause serious damage to the aquaculture industry in the long-term.
AQUACULTURE PRODUCTION PRACTICES: A PYRAMID
Aquaculture production practices have been represented as a pyramid, serving as a visual aid to categorize the broad ranges and levels of technology inputs practiced around the world (Figure 10-4; Tacon, 1988). At the base of the pyramid are relatively inexpensive aquatic animals produced under extensive conditions, (i.e., in large pond areas stocked at low densities with low inputs in terms of husbandry and nutrition technology) comparable to pasture production of cattle. Inexpensive organic material such as manure is used as a fertilizer to stimulate natural production as forage for the aquatic livestock, which are primarily herbivorous and omnivorous fish such as carp or tilapia or fresh water
crustaceans. In these extensive systems, seedstock can be purchased at low cost from fishermen or from local hatcheries or simply brought in by tidal action. Overall inputs, in terms of financial investment, levels of technology and skills required are very low, as are the associated risks.
The large volume in the center of the pyramid represents semi-extensive to semi-intensive production of aquatic livestock, which includes a broad range of species (omnivores, herbivores, carnivores) raised under a broad range of conditions. Inputs in terms of husbandry technology range from low to high, as does the relative sophistication of nutritional programs and required feeds. Farmers tend to use supplemental feeds and depend to varying degrees on the nutrition provided by natural food organisms to help sustain their aquatic livestock. Feed conversion ratios (FCR) can range from less than 1:1, where farmers take advantage of natural food contributions, to 1:4 or greater, in situations where supplemental feeds are largely inadequate to meet animal dietary requirements and/or where natural food production is limiting.
The peak of the pyramid represents intensive aquaculture, similar to intensive animal production, such as cattle feedlots or poultry production houses. Feeds used in intensive systems are usually complete in terms of meeting the animal’s nutritional requirements throughout the production cycle, and functional with respect to the required physical-chemical characteristics, such as water stability, buoyancy and organoleptic properties. Complete and functional
feeds are used to raise mostly marine carnivores, crustaceans and other high-value fish with a range in FCR of less than 1:1 for salmon to about 2:1 for other species. The very low FCR seen in salmon reflect a high level of nutrition and feed manufacturing technology in synch with sophisticated husbandry practices.
In the following descriptions of aquaculture operations, the convention of the pyramid is used to highlight relative position in the range of practices in aquatic farming.
Extensive Production Systems
Aquaculture in China is incorporated into everyday life with fish production ponds located near population centers and easily accessible to the marketplace. Traditional Chinese fish production systems are often integrated with farm animal production (e.g., manure from swine pens is used to fertilize fish ponds), thereby stimulating productivity of the aquatic food chain (Figure 10-5). In another type of extensive fish production system, aquatic plants are grown in one pond and used to feed grass carp in another (Figure 10-6). Likewise in Indonesia, large fleshy leaves are fed to herbivorous fish. These fish are aggressive eaters and quickly reduce leaves to veins (Figure 10-7).
Semi-Extensive Production Systems
Semi-extensive carp production is practiced in Poland and other parts of Europe with large ponds, stocked at low densities and use of whole grains as feedstock. Interestingly, pond production of the common carp has been practiced for so long in these areas that carp have been selected to have very few scales, reportedly because housewives successfully argued that they did not like to scale the fish. Feed inputs limited to whole grains result in a feed conversion ratio of over 3.5:1 in semi-extensive carp farming (Figure 10-8).
As an example of semi-extensive aquaculture practice used to raise shrimp, farmers in Vietnam use tidal action to bring in water to their ponds, not requiring the use of pumping stations, and this same natural influx of water can supply shrimp seedstock for the ponds. At the low stocking densities, less than five shrimp per square meter of surface area, natural productivity contributes strongly to the nutrition of the shrimp and there is little need for complete feeds. Shrimp are fed a locally made mixture of boiled trash fish and rice bran (Figure 10-9). Fresh water prawns are farmed in a similar manner in Thailand and fed supplemental, homemade feeds consisting of sun dried, cold-extruded, noodles made of rice bran and trash fish. In most of Latin America, where approximately 20 percent of the world’s shrimp are farmed, production systems are semi-intensive; farmers use diesel-powered or electric pump stations to supply water to large ponds, purchase seedstock from hatcheries or from local fishermen, and purchase supplemental and/or complete pelleted feeds that are commercially manufactured.
Intensive Production Systems
At the top of the pyramid are the intensive fish/shrimp farming systems, where nearly all production parameters and technology inputs are well controlled, including type and quality of seed stock (fry or postlarvae) and feed. In the case of intensive shrimp farming, postlarvae are purchased from commercial hatcheries where selective breeding may have started and where sophisticated laboratory techniques are used to screen for viral and other diseases. Intensive shrimp feeds are nutrient-dense, complete, and functional. For example, in Thailand, shrimp are farmed in small, uniform ponds less than one-hectare in size with heavy mechanical aeration used to maintain adequate concentrations of dissolved oxygen and to circulate water helping to keep organic waste in suspension and aiding its aerobic decomposition (Figure 10-10). Stocking densities are high, with yields of 6 metric tons per hectare per crop or greater. Intensive feeds that cost over $1.00 per kilogram can provide an FCR of about 1.4 to 1.7:1. These feeds are sold as small, highly compact, water stable pellets made of very finely ground ingredients, including marine proteins, sources of cholesterol, lecithin, attractants, and pigments. Feed trays are used to monitor feed consumption and shrimp health throughout the day. Phase-feeding is practiced to improve rate of weight gain, and water exchange is minimal to
help control diseases. Shrimp are harvested quickly by draining the small ponds and are immediately available for processing maintaining excellent product quality (Figure 10-11).
Intensive fish farming can be seen in Malaysia, where concrete ponds filled with tilapia are supplied with oxygen by aerators (Figure 10-12). Feeds used are nutritionally complete, floating, and extruded, contain about 30 percent crude protein and 5 percent fat, and can achieve an FCR of about 1.5:1. In many countries, floating cages are used to raise high-value marine fish such as sea bass and sea bream. Where manufactured feeds are not yet available, ground trash fish is used as feed. Other species, such as hybrid catfish and snakehead, are also intensively farmed in Asia. In Thailand, hybrid catfish are fed complete, floating, extruded feeds containing about 35 percent crude protein and, 6 percent fat with an FCR of about 1.2:1. Most of the hybrid catfish production is for domestic consumption rather than export, as is the case for shrimp.
Other intensively reared species of fish include salmon, trout, European sea bass, sea bream, yellowtail, catfish, and eel. All of these species receive complete, pelleted feeds. With the exception of channel catfish feeds, the feeds for these species contain substantial concentrations of fish meal. Feeds for aquatic species now account for over 25 percent of global fish meal production, up from less that 10 percent one decade ago. Given than fish meal production has been stable over the past decade, averaging 6.5 million metric tons per year, expanded production of these species will depend upon the development of alternative sources of protein from sources that can be increased in the future or diverted from other uses. This suggests that development of suitable protein sources from grains and oilseeds will play an important part in expanded production of intensively farmed fish species.
Four years were required for salmon to reach harvest size a decade ago; today, it takes less than two years for salmon to reach the same harvest size. This gain is the result of improvements in feed formulation, manufacture, and feeding practices, plus the development of vaccines that prevent infectious diseases. Similar advances are being made in the other species of intensively farmed fish.
The aquaculture industry requires more rapid development in three principle areas of technology required to support sustainable growth: nutrition, genetics and environment. In terms of nutrition and feeds, better understood nutritional requirements of fish and clearly understood production requirements of farmers are needed because of the great diversity of fish species used by the aquaculture industry. Appropriate technologies in feed formulation, manufacturing, and feeding are needed to help the industry parallel modern farm animal production systems and facilitate the transition from extensive to semi-intensive and intensive systems where natural resources can be more efficiently used.
In hatcheries, the dependence on live and fresh food organisms, especially microalgae and brine shrimp (Artemia) used to raise larval shrimp and fish must be replaced by commercial feeds to help control disease vectors and maintain consistent production. The world’s supplies of Artemia cysts have been in great decline, and high prices have made existing supplies unavailable to many farmers. Conventional larval feeds, including dry microcapsules, flakes, and powders, decompose rapidly in water, increasing rates of microbial loading, disease, and mortality of larval shrimp and fish. Liquid feeds, which consist of fully hydrated microcapsules stabilized in a probiotic liquid medium, are a new
category of larval feeds made by manufacturing methods that prevent excessive loss of nutrient bioavailability. Liquid feeds are superior to conventional dry larval feeds, reduce pollution, and can replace a greater proportion of live food organism used in hatchery feeding programs. Complete replacement of live foods remains a high priority for the industry. For grow-out fish and shrimp, more efficient feeds are needed, especially those that lower the amounts of enriching nutrients (e.g., nitrogen and phosphorus) that are excreted into the aquatic environment and contribute to eutrophication of waterways.
Strong emphasis must be placed on stock domestication and selective breeding programs to provide more predictable and consistent animal performance, especially in the case of shrimp. Most shrimp hatcheries continue to depend on wild-caught broodstock, which can carry diseases and can have low or variable fecundity and unpredictable animal performance. Efforts to develop disease tolerant or resistant strains of shrimp are underway in many countries, but ever-increasing varieties of new viral and bacterial pathogens make it difficult to keep up. Genetic improvements of most aquatic species are needed to help move the industry forward.
Advances in nutrition and genetic technologies must be accompanied by similar advances in bio- and other technologies to help control the aquatic microbial environment, especially in shrimp farming. That is, if the environment is not under control with respect to microbial ecology, then technologic advances in nutrition and genetics will not yield full benefits. The proliferation of more virulent bacterial and viral pathogens requires new and better approaches in the control of disease. This means a move to closed systems, which has already started in several countries, and a focus on disease prevention, not eradication, by managing microbial communities to maintain pathogens at levels that permit operation of profitable businesses (Moriarty, 2000).
Aquaculture presents global challenges, including great diversity in species, habitats, culture systems, and industry technology. World markets are diverse. In addition, the nutrient requirements of most fish species and the bioavailability of nutrients in many locally produced ingredients are not known.
The aquaculture industry needs to eliminate its dependence on capture fishery, both as a source of seedstock and as a source of feed ingredients, primarily fish meal. Feed programs need to be based on nutrient content rather than on ingredients. Closed aquaculture systems utilizing recirculated water must be developed to the point where production costs are competitive with systems depending upon flowing water. Domesticated strains of fish selected for economically important traits must also be developed. For some species of farmed fish, the sophistication of farming is approaching that of the poultry industry, but, for most others, fish farming is decades behind in terms of controlling inputs and outputs such that farming is sustainable, environmentally benign, and economic. Technologic advances in genetics, nutrition and
environment, must be made in parallel to achieve long-term industry sustainability.
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