Making fish farming more sustainable (2023)

The American Heart Association recommends eating fish at least twice a week because fish is high in protein, low in saturated fat, and high in omega-3 fatty acids. Global per capita fish consumption almost doubled from the 1960s to 2012. And today, about half of all seafood for human consumption is produced through fish farming, also known as fish farmingaquaculture.

The Food and Agriculture Organization of the United Nations (FAO) projects that by 2030, fish farming, one of the fastest growing methods of food production in the world, will be responsible for almost two-thirds of the fish we eat.

The most common type of aquaculture is aquaculture in net pens or cages anchored to the seabed in the ocean near shore. There are also closed systems of tanks or ponds that float on water or work on land. The FAO estimates that more than 600 aquatic species occur worldwide in a variety of aquaculture systems using fresh, brackish or salt water.

In the US, more than 91% of the seafood we eat is imported. China is the world's largest fish exporter, the third largest fish importer and the largest aquaculture producer. Already in the year 2500 a. C. The Chinese practiced fish farming by putting carp in paddy fields where they ate insects and weeds, fertilized the rice and then ate them. Today, 88 percent of global aquaculture comes from Asia.

Although fish is known for its omega-3 fatty acids, they do not produce omega-3 fatty acids themselves. They are produced by microscopic algae that live in fresh or salt water or in sediment. Herbivorous fish and forage fish such as sardines, anchovies and herring receive omega-3 fatty acids by consuming the microalgae. Larger carnivorous fish such as salmon or perch will eat the forage fish. Because salmon and other popular carnivorous fish need omega-3 fatty acids to grow, 30 to 50 percent of the fish food traditionally used for these species consists of fishmeal (ground fish) and fish oil. More than 50 percent of the world's fish oil is used as feed for farmed salmon.

This is one of the reasons why fish farming has a reputation for being unsustainable. In 1997 almost 3 tons of forage fish were needed to produce one ton of salmon. A third of the world's catch is still used to produce fishmeal and fish oil. As a result, forage fish are being overfished and some populations have collapsed, affecting the entire food web as larger fish depend on them for food.

Most fish farming methods are also detrimental to the ecosystem in other ways.

Fish waste and food scraps leak out of the nets into the sea, causing nutrient pollution. This can lead to a lack of oxygen in the water, which can stress or kill aquatic life. In addition, antibiotics or pesticides used on farmed fish can affect other marine life or human health. These nutrients and chemicals also sink to the bottom of the ocean, where they can affect biodiversity there.

Fish cooped up in nets or pens are more susceptible to stress, which can encourage diseases and parasites that can then spread to wild species.

Farmed fish sometimes escape to the sea, breed with wild species and affect the genetic diversity of the population as a whole.

Terrestrial closed systems minimize the amount of waste and nutrients released into the environment, prevent fish from escaping and limit the spread of disease. but pumping the water through them takes a lot of energy and the waste water still has to be properly disposed of.

Fish farming has also led to the conversion of land for food and the destruction of ecosystems. Huge areas of South America, almost 4 million hectares of forest, are cleared and converted to agricultural land every year to grow soybeans, which are used as food for herbivores and other fish. Soy cultivation also depends on the availability of water.

Shrimp farming, which normally takes place in salty coastal waters, has been responsible for the destruction of 38 percent of the world's mangroves. Mangroves have important ecological functions, including providing food and habitat for many species, preventing erosion, sequestering carbon, and protecting against storms. In addition, many shrimp ponds accumulate shrimp waste, antibiotics and pesticides, and without mangroves to filter, they eventually become useless.

But Pete Malinowski, former director of aquaculture at New York Harbor School and director of theBillion Oyster Project, which aims to restore a billion live oysters in New York Harbor, believes aquaculture's bad reputation is undeserved.

"Most aquaculture operations are much more sustainable than animal feed production," he said. “Aquaculture gets a bad rap because we see it as an alternative to natural environments like undeveloped coastlines, rather than comparing it to agriculture. In fact, aquaculture is a much more sustainable way of getting protein than farming.”

"Aquaculture does a lot of harm, but it's getting a lot better," Malinowski said. "People are being educated and it becomes unacceptable to farm fish in environmentally unfriendly ways."

How fish farming becomes more sustainable

One strategy is to move aquaculture to the open sea, where the water is clean and currents are strong and constant enough to continuously clean the farms of fish waste and pests such as sea lice. The open ocean also offers farmed fish a more consistent salinity and temperature. This means they are less stressed and less prone to disease, which encourages better growth and minimizes the need for antibiotics or vaccinations.

Blue sea open farmsfarm cobia (related to remoras) on the world's largest open ocean farm. After the fish hatch, they spend 14 months in huge underwater enclosures well below the surface in clean ocean waters seven miles off the coast of Panama.

Steve Page of Ocean Farm Technologies helped design thisAquapod, a geodesic dome large enough to house several hundred thousand fish. Kampachi Farms off the coast of Hawaii uses the Aquapod to grow Kampachi (related to the Yellowtail) after it has been successfully mountedVelella Project. The project investigated the feasibility of farming fish in an aquapod attached to a floating boat in deep water. It had no measurable environmental impact. However, since satellite communications were not robust enough to handle the remote controls needed to control the floating Aquapod, Kampachi Farm now uses an Aquapod attached to a barge in the ocean. In the future, aquapods could potentially be fitted with propellers and a GPS system and used to transport juvenile fish to their destination ready to be caught.

On land, some fish farms use recirculation systems to recycle their water. Recirculation systems use 100 times less water per kilo of fish than traditional land systems. In addition, water quality can be continuously monitored, reducing the risk of disease and the need for antibiotics.

Denmark is a leader in recirculating aquaculture. Hallenbaek Dambrug farms rainbow trout while more than 96 percent of its water is recirculated. The resulting waste water is filtered and the sludge is used for biogas or fertilizer. Waste water is treated to remove nitrate.

Anadramus fish such as salmon and trout hatch in freshwater, then migrate to the ocean and return to freshwater to spawn. Salmon and trout are typically raised in freshwater until they are mature enough to migrate to saltwater, where they are raised in sea cages. However, some new circulatory systems allow these fish to live their entire lives on land, alternating between freshwater and saltwater environments by controlling the chemistry of the water.

Scientists at the University of Maryland's Department of Marine Biotechnology have developed a circulatory system that enables predictable reproduction in farmed fish, one of the biggest challenges in aquaculture. The system recycles 99 percent of its water, filters waste through microbial communities, and produces methane for biofuel. By changing water temperatures, lighting and salinity, and then feeding the fish a pellet that mimics a hormone that stimulates reproduction, scientists were able to get the fish to reproduce in predictable cycles.

RDM Aquaculture, an indoor brine shrimp farm in Indiana, has been recycling the same water, producing zero waste and using no chemicals for five years. Its "heterotrophic biofloc system" allows all organic matter (shrimp waste, bacteria, microalgae, shrimp shells and dead shrimp) to remain in the water. Shrimp eat what they need and bacteria feed on their waste.

Thierry Chopin, a professor of marine biology at the University of New Brunswick, combines species from different levels of the food web in a practice called "integrated multitrophic aquaculture". Working with Cooke Aquaculture in New Brunswick, Canada, Chopin places mussels and seaweed downstream from salmon pens. The mussels feed on salmon waste while the algae absorb inorganic nutrients. Sea urchins and sea cucumbers consume larger particles on the sea floor. Cooke's salmon and mussels are sold as food, and its seaweed is used in restaurants and in the manufacture of cosmetics.

A Dutch and Vietnamese industry group, together with universities and research institutes in Vietnam, are designing a 'nutrient system' aquaculture concept that uses a pond's natural ecosystem to raise fish or shrimp and dispose of waste. The project studies how omega-3 fatty acids are produced and determines the right balance of algae and bacteria to ensure the best water quality, fish and shrimp nutrition and waste decomposition.

Rising fish feed prices and the environmental impact of overexploitation of forage fish for food and fish oil have led to an increase in farming of herbivorous fish (such as carp and tilapia) and omnivorous fish (barramundi), which require much less fishmeal. to produce protein. In the meantime, alternatives to fishmeal feed are also being researched or made more sustainable.

new types of food

• Kampachi Farm has experimented with fish diets supplemented with soybeans and plant matter, substituting microalgae and yeast products for fish oil. In 2013, Kampachi tested three foods that didn't contain fishmeal and found that they were all comparable to the standard diet. Researchers at the University of Maryland Center for Environmental Sciences developed fish food made entirely from corn, wheat and soybeans. Fish oil has been replaced by fatty acids from algae, amino acids and soy or canola oil. The PCB and mercury levels in the fish were 100 times lower than those in fish consuming fishmeal feed. This is because fishmeal and fish oil in feeds can transfer environmental pollutants to farmed fish, while feeds made from plant-based ingredients can reduce them.

• British scientists modified Camelina sativa, a plant known for its seed oil, with genes synthesized from algae, allowing the plant to produce omega-3 fatty acids that successfully replaced fish oil in fish feed; the salmon thrived.

• A Texas A&M University scientist uses dried still grains with nutrient-dense soluble grains made in ethanol production as a cheap source of protein in shrimp feed. It has successfully replaced distiller's dried sorghum and corn kernels with 10 percent of the protein in shrimp feed.

• Calysta, a California-based company, develops feed proteins using bacteria that are fermented and fed methane gas in a process similar to making beer or bread. The product, called FeedKind, is a natural, high-quality protein fishmeal substitute.

• Researchers are from Wageningen University in the Netherlandsexperiment with insectsas a new source of omega-3 fatty acids. Scientists extracted the naturally produced oil from a variety of insects and are studying reproduction, optimal nutrition and processing of insects into oil. A 2014 FAO paper concluded that insect meal could replace 25-100% of soybean meal or fishmeal in fish diets with no adverse effects.

In 2010, only 36% of fishmeal came from the trimmings and trimmings (heads and guts) of fish fillets, which are typically discarded. China is increasingly dependent on wild-caught fish for fishmeal and fish oil. A Stanford University study found that using scrap from seafood processing plants and adding seaweed or ethanol yeast to increase protein content (because the scrap contains less protein than farmed fish) could replace half or two-thirds of the fishmeal currently used . in Chinese aquaculture.

Finding the best fish feed formulas also means achieving the lowest feed conversion ratio - the amount of feed consumed in relation to the weight gain of the fish. For example, Malinowski explained, tilapia can produce a pound of protein with less than a pound of feed, while salmon requires a pound and a half of feed to produce a pound of protein.

"It depends on how you grow them: the right stocking density, water quality and nutrient-rich forage all result in good conversion to protein," he said. "And the lower the feed conversion, the more profitable the farm becomes because feed is so expensive."

As the world population grows to 9 billion by 2050, more people enter the middle class, and fisheries become overfished, fish farming will be critical to providing the world with the protein it needs.

How do we ensure that aquaculture is sustainable?

As there are a number of different international and national aquaculture certification schemes, the FAO has developed technical guidelines for aquaculture certification and an assessment framework. But while environmental impact assessments and certifications are required for many large fish farms, they are not for small fish farms, many of which are unsustainable. Regulations for developing responsible aquaculture are weak in many countries.

• The World Aquaculture Alliance developed the voluntary programCertification of best aquaculture practices.The standards address environmental and social responsibility, animal welfare, food safety and traceability.

• ThatAquaculture Stewardship Council, founded by the World Wide Fund for Nature and the Dutch Sustainable Trade Initiative, also aims to make fish farming environmentally sustainable and socially responsible. Its goal is to be the world leader in certifying responsibly farmed seafood and administering global standards for sustainable aquaculture.

• The World Wide Fund for Nature, the FAO, the World Bank and others formed theShrimp Aquaculture and Environment ConsortiumAdoption of international principles for responsible shrimp farming.

• This was created by the Dutch development organization SNV and the International Union for Conservation of Naturemangroves and marketsProject in Cà Mau, Vietnam to promote sustainable shrimp farming. The project provides training for producers on how to sustainably farm and market certified shrimp, promotes the reforestation of mangrove forests and helps shrimp farmers become certified for carbon markets. These shrimp farms must have 50 percent mangrove growth or more.

In a sign of continued growth in fish farming, NOAA Fisheries recently released a new rule opening federal waters to aquaculture from three to 200 miles offshore in the Gulf of Mexico.

"There aren't enough shellfish left in the ocean to meet our needs," Malinowski said. “All major commercial fisheries are in decline or collapse. So if we want to continue eating shellfish, aquaculture is the only way and we need to do it in a more sustainable way.”

To ensure you are choosing sustainably farmed seafood, visit usShellfish monitoring.

a new report,ThatStatus of sustainability initiatives: standards and the blue economyanalyze themMarket and performance characteristics of international sustainability standards applicable to both the wild capture and aquaculture sectors.