HG平台现金网Kelp from a test site run by WHOI researcher Scott Lindell being harvested at the end of the growing season. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)
What is aquaculture?
Aquaculture is the farming of aquatic animals or plants principally for food. It includes the breeding, rearing, and harvesting of fish, mollusks, crustaceans, and plants in fresh and saltwater environments. The practice originated in China about 4,000 years ago, and global production continues to be dominated by China and other Asian countries. Aquaculture is used to produce food by some of the poorest communities around the globe as well as by major corporations.
HG平台现金网Globally, aquaculture already supplies more than half of all seafood consumed by humans, a proportion that continues to rise as the world population grows. According to the Food and Agricultural Organization (FAO), 3 million tons of food were produced by aquaculture in the 1970s, a figure that rose steadily to over 80 million tons in 2017.
HG平台现金网More than 550 aquatic species are farmed. The top fish species include carp, catfish, salmon, and tilapia; commonly farmed shellfish include shrimp, oysters, clams, mussels, and scallops. Newer to the marine aquaculture menu are various species of seaweed. Aquaculture also includes the production of fish for the aquarium trade and plants for the pharmaceutical, biotechnology (e.g., biofuels), and health industries. It is also used to replenish depleted fish stocks in the wild; the majority of “wild” Alaskan salmon come from hatcheries.
Who are the leaders in aquaculture production?
HG平台现金网While the United States is one of the world’s leading consumers of seafood, it only ranks 16th in total aquaculture production according to the FAO. Americans consume nearly 5 billion pounds of seafood annually, and over 85% comes from overseas. China is firmly at the top of the global aquaculture leaderboard, producing nearly 60% of farmed seafood. Other leaders include Indonesia, India, and Vietnam. As the global demand for seafood continues to rise, the FAO, National Oceanic and Atmospheric Administration (NOAA), and other groups are outlining strategies to boost new U.S. aquaculture production. Some of the challenges in the U.S. thus far include regulatory and policy hurdles (e.g., the need to secure permits to farm in state and federal waters), as well as a reluctance by more established commercial and recreational interests to share the marine environment.
What are the methods used in aquaculture production?
HG平台现金网Many different aquaculture production systems are in use around the world, each with its own pros and cons. Commonly used systems for fish include ocean cages, coastal or freshwater ponds, and fully-enclosed systems on land; systems for shellfish and seaweeds are suspended in the ocean by ropes attached to floats and anchors. Many aquaculture systems involve a first phase in a hatchery, where eggs (fish and shellfish) or spores (seaweeds) are raised to juvenile stages before being transferred to ponds or the ocean, where they grow into adults.
HG平台现金网Marine fish such as salmon are often farmed using ocean cage systems, which allow for the free exchange of water between the farm and the environment. In its brief 50-year history, marine fish farming encountered many early challenges from untested management practices and had to learn to cope with diseases, waste deposition, escapes, and interactions with other marine life. Most of those challenges have been addressed by modern management methods and technologies, such as the regular fallowing of farm sites, vaccinations, advances in nutrition and feed delivery, and enhanced farm monitoring.
Tilapia and shrimp are often farmed in semi- or fully-enclosed ponds where water exchange is controlled. Normally, the waste discharged with effluent water is biologically treated before it enters the natural environment. If not properly managed, pond-based aquaculture systems can degrade downstream environments and contribute to the destruction of wetlands and mangroves.
Systems that pose fewer risks to the surrounding environment include land-based recirculation systems that also treat and discharge relatively small volumes of the water to the environment. Fish farmed in this manner include salmon, Arctic char, tilapia, and sea bass.
HG平台现金网Suspended or “longline” aquaculture systems—which can be located nearshore or offshore —are used to raise shellfish and seaweeds. Shellfish eat plankton that they filter out of the water, and seaweeds absorb dissolved nutrients; neither needs additional inputs of food or fertilizer. These systems consist of tensioned and submerged horizontal ropes held in place by anchors and buoys from which shellfish or seaweeds are suspended by ropes. Shellfish can also be raised on trays or inside mesh bags hanging from ropes in the water.
Why is aquaculture important?
Aquaculture is playing an increasingly important role for the planet as a food and potential energy source. As the most rapidly expanding sector of food production, marine aquaculture is one of the fastest, most resource-efficient ways to produce protein, according to the U.S. National Oceanic and Atmospheric Administration (NOAA). Marine aquaculture has already helped improve nutrition and food security in many parts of the world where wild fish stocks have collapsed. Looking ahead, it could be the answer to a major food sustainability challenge. Scientists at WHOI estimate that, at a minimum, we need to increase food production by at least 50% over the next 30 years to sustain the projected global population. In those decades, land-based food production in many regions will be challenged by climate change, freshwater shortages, and a lack of new arable land. New food supplies must come from the ocean, which covers more than 70% of Earth’s surface, yet currently supplies only 2% of our food.
Marine aquaculture also holds great promise to meet the world’s growing energy needs. Demand for energy is increasing 1-2% per year, driven by a growing population and increasing economic development. HG平台现金网 90% of our energy presently comes from oil and gas, which are finite natural resources and contribute to climate change. Researchers have turned to biofuels—fuels generated by biological processes—as a potentially renewable source of energy that can in principle be carbon-neutral. Biofuels from land-based sources such as corn and sugarcane require arable land, fertilizers from fossil fuels, and scarce fresh water, whereas biofuels from marine algae and seaweeds require only sunlight and abundant seawater.
In addition to meeting two critical human needs—food and energy—aquaculture provides valuable services for marine ecosystems. Rather than producing greenhouse gases like land-based livestock, shellfish and seaweeds take up carbon dioxide, and dense seaweed farms can create a “halo-effect” around them that could help mitigate local ocean acidification. For these reasons, environmental organizations such as the World Wildlife Fund and The Nature Conservancy actively champion shellfish and seaweed farming.
Given aquaculture's potential, scientists are working with resource managers and companies to find safe ways to scale up production in the U.S. and globally. Key challenges in basic engineering and biology remain. These include developing the tools to operate and monitor large-scale aquaculture systemsHG平台现金网 in ways that have the least impact on ocean ecosystems and people.
What are the impacts of aquaculture on the marine environment?
Whether on land or in water, all farming practices have some impact on the natural environment. As described above, fish and shrimp farming can have negative impacts if not carried out in an ecologically sound way. New farming practices of integrating shellfish and seaweed culture with fish farming can reduce impacts and enhance the environment. In fact, shellfish and seaweed farms can improve water quality by taking up excess nitrogen and carbon, and by providing structures in the water column that become nurseries for important fisheries.
How is aquaculture regulated?
HG平台现金网Aquaculture regulations vary from country to country. In the U.S., several federal and state agencies are involved in aquaculture regulations, and the permitting process for new facilities can be lengthy and complicated. The primary federal agencies charged with regulating aquaculture include the Food and Drug Administration (FDA), the Department of Agriculture (USDA), the Environmental Protection Agency (EPA), the Army Corps of Engineers (ACOE), and National Oceanic and Atmospheric Administration (NOAA). Each is responsible for a different aspect of aquaculture programs. For example, ACOE works with NOAA to issue permits authorizing aquaculture licenses, whereas EPA regulates wastewater discharge and the use of chemicals in aquaculture facilities. Although existing federal statutes provide a framework for regulation, critics say that none addresses aquaculture directly, and state regulations for different kinds of aquaculture facilities vary considerably. Critics also suggest that there is no way to ensure that regulations are uniformly enforced.
What are scientists doing to advance sustainable aquaculture?
There is a strong push to scale up aquaculture production in the U.S. and around the world, and to address the challenges of implementing and maintaining large-scale farms. For example, scientists are working on ways to mitigate the impacts of climate change on aquaculture farms. They are investigating the best location for future farms as climate change generates new circulation patterns, warms coastal waters, and changes ocean water chemistry. As carbon dioxide accumulates in the atmosphere, the ocean absorbs more carbon dioxide, leading to ocean acidification. Over time, this reduction in seawater pH dissolves the calcium carbonate shells of marine organisms such as oysters, mussels, and clams. WHOI scientists are investigating a strategy to mitigate this problem by adding a safe and natural chemical buffer (e.g., sodium bicarbonate) to seawater to absorb the impact of acidification on the most sensitive early stages of shellfish in hatcheries.
Another threat to shellfish farms comes from harmful algal blooms (HABs), such as red tides. Occasionally, certain species of algae that grow in the ocean burst into “blooms” that accumulate in visible patches near the surface of the water. A subset of these produce toxins that work their way up the food web and are consumed by shellfish. People who inadvertently eat the infected shellfish can suffer severe gastrointestinal impacts such as vomiting and stomach pain, paralysis, amnesia, and even death. Occasionally, blooms can stunt or kill the shellfish. In response, scientists are investigating ways to keep the coastlines clear of excess nutrients that can fuel algal blooms. They are also investigating the use of new genetic tools to breed desirable traits into aquaculture species to make them more resistant to disease and climate change.
HG平台现金网There are many exciting projects underway to scale up aquaculture production. For example, one major challenge identified by the research community is the need to routinely monitor aquaculture farms—a difficult task if farms are located offshore. Scientists are developing new robotic vehicles (and modifying existing ones) to autonomously sample and monitor offshore aquaculture production. Researchers are also working to breed new strains of the seaweed called sugar kelp—a promising future biofuel—to increase its yields and to develop varieties that can withstand a warming ocean.
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