Aquaculture is the commercial farming (breeding, raising, and harvesting) of aquatic plants and/or animals in tanks, ponds, or net pens in the ocean. Mariculture, marine aquaculture, is most frequently practiced in sheltered coastal waters but also in offshore and underwater habitats.
Aquaculture farms primarily raise fish (carp, salmon, tilapia, and catfish being most common), crustaceans (primarily shrimp), molluscs (oysters, mussels, and clams), and aquatic plants (algae and seaweed).
Aquaculture has been around for centuries. Chinese farmers started raising carp in their rice fields at least 2,500 years ago and many other cultures have also raised aquatic life for food since then. In the last 50 years, however, aquaculture has begun to be industrialized. Since 1980, aquaculture has expanded roughly 14-fold. By 2012, aquaculture accounted for nearly half of all fish and shellfish consumed worldwide.
Seafood is the world’s largest traded food commodity with 3 billion people relying on wild-caught and farmed seafood as their primary source of protein. The planet’s increasing human population means growing global food needs and a growing demand for seafood.
Unfortunately, 75% of commercial fishing is currently at or beyond sustainable levels with many fisheries in danger of collapse. (A fishery collapse is when the population or harvest rate of a fish or shellfish species drops to less than 10% of original numbers making fishing no longer sustainable.) With increasing seafood demand and decreasing wild seafood supply, aquaculture can help to make up the difference. Approximately 42% of the seafood we currently consume is farmed (more fish is cultivated than beef!).
While aquaculture could be the key to food security in the future, the industry first needs to address some of its issues. Solutions for many of these threats already exist, but require prioritization and regulations so that they are widely accepted.
Wild Fish Feed Farmed Fish
The diet of wild piscivorous (fish-eating) fish species, like salmon, consist primarily of other fish. When these fish are raised in farms, their feed also consists primarily of fish, fish meal, and fish oil. Therefore, wild fish must be caught to feed some farmed fish.
In these cases, aquaculture can consume more fish than it produces; several pounds of wild fish can be necessary to produce one pound of farmed fish. And those needs add up: 98% of the global catch of anchovies, the most heavily fished species in the world, are turned into fish meal and fish oil with aquaculture consuming over 70%.
It is important to note that piscivorous farmed fish represent only 13 percent of aquaculture (by weight); other farmed aquatic animals (like plant-eating fish species) do not have the same wild fish food needs. And farmers are experimenting with other sources of protein in fish feed (soybeans and other grains), reducing aquaculture’s demand for wild fish.
The greatest threat to the world’s mangrove forests is the shrimp aquaculture industry. Shrimp farms are built in coastal environments, home to mangrove ecosystems. Hundreds of thousands of acres of coastal wetlands have been cleared to make room for artificial ponds to grow shrimp. And there are indirect threats to mangroves as well. To create these ponds, channels are dug in the sea floor which diverts the natural flow of water affecting surrounding mangrove forests by affecting seed dispersal and cutting off fresh water sources. On top of this, shrimp farmers use pesticides and antibiotics to keep the shrimp disease-free. These chemicals, along with huge amounts of shrimp waste, contaminate the surrounding coastal waters, further damaging the nearby habitat.
It’s not just shrimp. Salmon farms are typically located in more remote coastal ecosystems. A farm with 200,000 salmon creates more waste than a medium-sized city. This waste, usually untreated, flows into the surrounding aquatic environment, polluting otherwise pristine habitats with waste and chemicals.
Disease & Parasites
Unlike in the open ocean, farmed marine species are often raised in close quarters and exclusively with other members of the same species. This close contact and lack of interaction makes the animals more susceptible to viral and bacterial diseases and makes disease transmission easier. The conditions are also well-suited for parasites, such as sea lice, which cause skin erosion, bleeding, and congestion in fish. To combat these issues, antibiotics are often given to the animals, which can increase bacterial resistance. The problems worsen if diseases (especially foreign pathogens), and even antibiotics, are inadvertently spread to wild populations and into open habitats causing other environmental hazards.
Fish waste is organic and composed of nutrients. In wild species that move freely in the ocean, the waste is spread over a larger area. With in-ocean aquaculture, fish waste is concentrated and is found in a higher volume due to both the large number of animals in a confined space as well as the decomposition of uneaten food. This leads to the release of organic waste into the ocean, especially nitrogen and phosphorus. This waste can collect on the ocean bottom which decreases dissolved oxygen levels and promotes algal growth leading to algal blooms both of which increase the possibility of ocean dead zones, with such low concentrations of oxygen that most marine life cannot survive.
There are several ways in which aquaculture can introduce non-native species into an environment. First, there is a risk of the farmed fish escaping their enclosure. Once in the ocean, they can interbreed with wild counterparts, diluting wild genetic stocks (interbreeding has been found to reduce lifespans and decrease vitality, and reduce production). Introduced species can spread foreign diseases to local species, and compete with local species for resources, sometimes out-competing them and decimating the local populations.
Secondly, if live non-local marine plants or animals are used as feed, without proper controls these too can escape or spread and disrupt the local ecosystem.
As with land-based animal agriculture, there are concerns for the well-being of the farmed animals. Crowding constrains normal swimming behavior which can increase aggression, competition for food, territorialism, and even cause cannibalism not seen in wild populations. This increased aggression risks injury to the fish which also increases the chances of disease. Additionally, the number of animals in confined spaces can result in lower water quality, with high concentrations of waste and inadequate oxygen in the water leading to increased stress, and in some cases, suffocation.
Like land-based farms, the aquaculture industry is largely based on consumption and growth, not conservation. As a consumer, you have the ability to research the source of your seafood to support companies that are ethically and sustainably producing. Remember that not all aquaculture is equal; there are a tremendous number of variables including the species farmed, the procedures used, and the values of the company. Awareness and education are essential to making responsible seafood choices. The amount of impact we can have on the aquaculture industry depends, to some degree, on where we live; but we have complete control over our individual choices.
Educate Yourself on the Source of Your Seafood
Whether at the supermarket or a restaurant, consider not only the type of seafood you choose, but also the source. Was it wild caught or farm raised? And in either case, what methods were used?
Support Regulations on Aquaculture Procedures and Imported Aquaculture Products
Many factors influence the environmental impact of aquaculture, from the content of the feed given, to the location and construction of the sea cages or pens to the water quality and procedures for maintaining it. Many producers are voluntarily making these changes by switching to plant-based protein in feeds, moving farms away from vital coastal ecosystems, and using nature-based (rather than chemical) solutions to parasites by introducing cleaner fish to the farms. Industry regulation and monitoring can ensure the widespread use of these solutions.
Support Environmentally Responsible Farms and Corporations
Aquaculture farms working to minimize (or even remove) their environmental impact should be recognized and patronized. Removing the use of chemicals and antibiotics, avoiding overcrowding, using natural water filtration systems all minimize ecosystem issues. Some companies are developing ways to use fish waste as fertilizer on land, minimizing waste and creating circular and natural resources. Aquaculture farms that raise multiple species (fish, shellfish, and seaweed) create a balanced aquaculture ecosystem with one species filtering the waste of another and providing nutrients to yet another.
Support Organizations Creating Responsible Aquaculture Around the World
A number of organizations fund aquaculture education and training in developing countries. The goal is to minimize habitat destruction and teach responsible aquaculture methods while providing a valuable source of income and nutrition.
Eat Further Down the Food Chain
All species are connected through a food chain. Plants get energy from the sun, animals eat plants, other animals eat those animals, and it goes on. If we eat something higher on the food chain, more energy was required to produce it than food closer to the source (the sun) making it a less efficient energy source. For example, it takes 1000 pounds of seagrass to produce 100 pounds of the blue tangs who eat it. Similarly, those 100 pounds of blue tangs produce 10 pounds of grouper or jackfish which are necessary to produce 1 pound of shark or tuna. The higher we eat up the marine food chain, the larger our impact on the ocean. Farmed carnivores (meat eaters) have a larger environmental impact and requirement than plant-eating species of fish. Farmed bivalves (oysters, mussels, and clams) have a neutral or even positive impact on the ocean; they filter water and can significantly improve the water quality.
There are a number of organizations working to educate consumers and fishermen about responsible aquaculture. Others are working to create and enforce regulations.
Learn more aquaculture and about these organizations below.
Hui o Kuapa, Hawaii
This organization is revitalizing traditional Hawaiian aquaculture, practiced for 2000 years. They create fish ponds on the coasts and turn them over to local communities for management. The focus is on the relationship between water, fish, land, mangroves, and using the balance of nature to create food security on small, isolated islands.
Veta La Palma, Spain
Incredible example of commercial aquaculture with the health of the ecosystem as the top priority. This fish farm is regenerating the local environment, farming sustainably, restoring the landscape, and reducing carbon in the atmosphere, all while making a profit. Their priority is the long term; producing less in the short-term to ensure production will continue into the future.
This ocean farming movement was founded by a former fisherman who saw a need for sustainability in marine food sources. GreenWave is spreading over all coastal regions of North America and to other countries around the world with the message of farming things that don’t require fresh water, feed, or fertilizer: kelp, mussels, scallops, and oysters.