Aquaculture

DEFINITION: Production of marine and freshwater food sources in controlled, farmlike environments in ponds, canals, lakes, and confined coastal areas

Although aquaculture provides a good source of protein for the demands of a growing world population, as well as an economic endeavor for some, like many forms of farming it is not without its negative environmental impacts. Residues from fish wastes, pollution, coastal erosion, and impacts on adjacent species are some of the challenges to sustainable forms of aquaculture.

Aquaculture is one of the fastest-growing forms of food production in the world. It includes the processes of propagating, raising, and processing marine and freshwater food sources such as fish, shellfish, and even kelp. In some cases by-products of the production of these commodities produce fertilizers and feeds for other animals. Ornamental products such as cultured pearls are also produced within aquacultural systems.

The practice of aquaculture is not new. Fish farming has been a part of the cultures of Pacific islanders and Southeast Asian peoples for centuries. Early forms of aquaculture were quite rudimentary compared with modern techniques, however; they provided foods and other products on a limited scale, mostly for local villages. In the twenty-first century, sophisticated aquaculture systems control the complete life cycles of the fish and other animals under cultivation. In many of these modern facilities, automated feeding and harvesting systems alleviate the need for labor-intensive practices, reducing the costs of production. In some cases, however, because of the nature of the commodities, intensive human labor is still required. Oysters, for example, are harvested from beds and then must be opened by hand, a process known as shucking, so that the integrity of the shells is maintained for the seeding of a future crop.

One of the elements that has spurred the development of aquaculture is the decline in production in fisheries in the open oceans owing to overfishing. According to the United Nations Food and Agriculture Organization (FAO), all major fishing regions in the world are now being fished intensely, with industrial fishing occurring in half the world's oceans. The needs of the growing world for protein and water affecting natural sources of seafoods have also contributed to the growth of aquaculture.

Industry Growth

Commercial aquaculture ventures have been established in nations throughout the world. The majority of these operations utilize naturally existing water sources in coastal regions, canals, or rivers; others are built at sites where traditional agriculture could not take place. An ideal aquaculture site has certain conditions that are favorable to the healthful management of the stocks of fish and other animals produced. These include clean water, appropriate water temperatures and levels of dissolved gases, good site topography, and food sources.

In the United States aquaculture operations are found in coastal regions and in dry interior areas, where ponds or rivers are used. Clams and oysters are harvested from beds in the marine of Washington State’s Puget Sound, for example, while in the eastern interior of the state, the Columbia River provides a freshwater source for the raising of salmon, trout, and steelhead, all for commercial uses. In dry west Texas, gravel pits filled with saline waters were some of the first ponds used to cultivate shrimp, an industry that now supplies millions of pounds annually from ponds filled with natural saline water. The state of Virginia has developed a large aquaculture industry, growing clams and oysters in hatcheries.

Crawfish, tilapia, trout, shrimp, cod, clams, oysters, frogs, and catfish are just some of the products found in aquacultural operations in the United States. According to the U.S. National Oceanic and Atmospheric Administration, shellfish, such as oysters, clams, and mussels, account for 80 percent of the total output of the U.S. aquaculture industry in 2020; salmon and shrimp accounted for most of the remaining percentage.

The monetary value of worldwide aquaculture production was some $204 billion in 2020. According to FAO, the top ten aquaculture-producing nations in 2019 were, in descending order, China, Indonesia, India, Vietnam, Chile, Norway, Bangladesh, Japan, Thailand, and Egypt. The United States ranked eighteenth in 2020, with an aquaculture industry that contributesd about $1.5 billion to the nation’s domestic economy.

Environmental Concerns

Aquaculture operations have a number of negative environmental impacts. Among these is that they generally require the installation of a considerable amount of technology, and thus disturb existing habitats, and they use large amounts of energy. Feed must be supplied to penned fish, and from the fish must somehow be managed. Diseases must be controlled, not only within the fish and other seafood stocks but also with respect to the possible spread of disease to adjacent native fish and other organisms outside the aquaculture pens or ponds. A particularly controversial element of aquaculture involves the genetic modification of many forms of fish stocks to enhance their ability to grow quickly under confined conditions. Critics of these practices question the safety of eating such fish and have also voiced concerns that if genetically modified species escape their aquaculture pens they may introduce unforeseeable problems into natural fish populations.

In many aquacultural settings, self-contained ecosystems are set up to supply nutrients for fish stocks. In some cases and even commercial fertilizers have been used in such ecosystems to stimulate the production of phytoplankton, which in turn is eaten by zooplankton and bottom dwellers. These are then eaten by fish stocks within the pen or pond. Unless a consistent flow of water can be maintained through the pen area where the fish stock is raised, the bottom can become silted up with waste. In confined estuaries this condition can have negative effects on fish outside the aquacultural operation. It has been suggested that the decay of fecal matter at the bottom of aquaculture pens and in areas where concentrated fish-rearing operations are conducted can contribute to the depletion of oxygen levels in the water near the bottom. This is especially the case if water currents are not efficient enough to purge the buildup of waste at the bottoms of these ponds and pens.

Shrimp, a major commodity grown aquaculturally, is a good example of some other environmental concerns. Aquaculture operations sometimes use antibiotics to control the diseases that shrimp are prone to acquire when they are being raised in confined areas. During the early part of 2000, the European Union banned shipments of shrimp containing chloramphenicol, an used on shrimp that has been found to be dangerous for human health. In addition, fishing communities and coastal residents have been critical of shrimp aquaculture, asserting that it reduces fish catches because it has negative impacts on coastal habitats and because it uses wild fish as food for the shrimp being raised.

Additional concerns about the negative environmental impacts of aquaculture have to do with the use of pesticides and other chemicals in the management of unwanted organisms in aquacultural waters. To control infestations of fish lice, for example, aquaculture operations often disperse pesticides into the water. Other chemicals are often used to cut down on growth on the nets and floats used in pen operations.

Within food webs or trophic levels, energy flows from lower to higher levels. If a larger fish eats a smaller fish, not all of the energy available from the smaller fish is passed on to the larger. This transference of energy is known as ecological efficiency. Aquaculture can exhibit very low levels of ecological efficiency. For example, farm-raised salmon are reared on food made from other fish, which are caught and ground up before being fed to the salmon as pellets or in meal form. It has been estimated that it takes 10 grams (0.35 ounce) of feed to produce 1 gram (0.035 ounce) of salmon. Considering the pressure already existing on wild fish stocks, it has been argued that this low level of ecological efficiency is a considerable detriment for the economy of aquaculture. In contrast, some kinds of aquaculture operations, such as catfish farms, are relatively ecologically efficient, and catfish, which are herbivorous, require no fish-based foods.

Aquaculture operations are also sometimes negatively affected by environmental conditions that come from outside their confines. Along coastlines and in low-lying areas, for example, pollution from agricultural can cause fish kills such as those that have taken place in aquaculture installations in Indonesia, Malaysia, and the Philippines. Washington State enacted a law to control the flow of manure effluent from dairy farms into the Nooksack River. Prior to the control of this pollution, coastal clam beds managed by the Lummi Nation were decimated; this aquacultural operation recovered after passage of the law.

Bibliography

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