Farm fishing, formally called aquaculture, is the practice of raising fish, shellfish, and aquatic plants in controlled environments rather than catching them from the wild. In 2022, aquaculture surpassed wild-catch fishing for the first time in history, producing 94.4 million tonnes of aquatic animals and accounting for 51 percent of all aquatic animal production worldwide. It ranges from simple earthen ponds stocked with catfish to high-tech indoor tanks with computer-controlled water filtration.
How Farm Fishing Works
At its core, farm fishing means controlling the life cycle of aquatic species: hatching eggs, feeding the animals, managing water quality, and harvesting at market size. The specific setup depends on the species and location, but operations fall into three broad environments.
Freshwater systems include ponds, pens, and cages placed in lakes or rivers. These are the most common globally and produce species like carp, tilapia, and catfish. Some freshwater farms are as simple as a dug-out pond fed by rainwater, while others use concrete raceways where water flows continuously past the fish.
Coastal and brackishwater systems sit where freshwater meets saltwater. Shrimp farms are the most recognizable example, typically using shallow ponds built along tropical coastlines in countries like Thailand, Ecuador, and Vietnam.
Marine systems operate in the open ocean or near the coast. Salmon farming in Norway, Chile, and Canada relies heavily on large net pens anchored in sheltered bays. Oyster and mussel farms use ropes, rafts, or stakes suspended in seawater. Newer offshore designs include submersible cages that can descend to depths of 55 meters to avoid surface storms and reduce coastal pollution, though these remain relatively niche.
What Gets Farmed
The species most people picture when they hear “fish farming” are salmon and shrimp, but globally the picture looks quite different. The single largest category is carp and related freshwater fish, which made up nearly 25 percent of all aquaculture production in 2021, at over 31 million tonnes. Most of that comes from China and South Asia, where carp is a dietary staple.
Seaweed is the second-largest product by volume, with brown and red seaweeds together accounting for about 28 percent of global output. Marine shrimp and prawns come next at 7.3 million tonnes, followed by oysters at 6.7 million tonnes. Tilapia, catfish, and salmon round out the top ten. In practical terms, if you eat farmed seafood in North America or Europe, it’s most likely salmon, shrimp, or tilapia. If you’re in Asia, it’s far more likely to be carp or shellfish.
Recirculating Aquaculture Systems
One of the fastest-growing approaches is the recirculating aquaculture system, or RAS, which raises fish entirely on land in closed-loop tanks. Water cycles continuously through a series of treatment stages: a settling basin or filter removes solid waste, a biological filter uses bacteria growing on plastic or sand media to break down ammonia (which fish excrete and which is toxic at low concentrations), and an oxygenation system injects pure oxygen or aerates the water before it returns to the fish tank. Some facilities add ozone or ultraviolet sterilization to kill bacteria and break down organic compounds.
Because nearly all the water is recycled, RAS facilities use a fraction of the water that ponds require, and they can operate anywhere, including landlocked cities far from the coast. The tradeoff is high energy and infrastructure costs. These systems are increasingly used for Atlantic salmon, trout, and barramundi in the United States, Canada, and northern Europe.
The Feed Question
What farmed fish eat is one of the most debated aspects of the industry. Carnivorous species like salmon need protein-rich feed, which has traditionally come from wild-caught fish ground into fishmeal and fish oil. For salmon specifically, producing one kilogram of farmed fish has historically required roughly four kilograms of wild fish to supply the oil component of the feed. That ratio has improved over the past two decades as producers have substituted vegetable oils and plant proteins, though this shift comes with its own consequences.
Farmed salmon is widely promoted for its omega-3 fatty acid content, but omega-3 levels in farmed salmon have actually dropped compared to a decade ago because of the increased use of vegetable oil in feed. The fish oil that once boosted those levels is being partially replaced by soy, canola, and other plant-based alternatives. Farmed salmon still provides well over 100 percent of the recommended daily intake of omega-3s in a standard serving, but the gap between farmed and wild fish has narrowed in ways that weren’t true a generation ago.
Environmental Concerns
The environmental impact of farm fishing varies enormously depending on the species, the system, and the location. Open net pens used for salmon farming draw the most scrutiny. These underwater cages hold hundreds of thousands of fish in a porous enclosure, and water flows freely between the farm and the surrounding ocean. That means parasites, bacteria, and viruses can pass from farmed fish to wild populations swimming nearby.
Sea lice are a well-documented example. These parasites thrive in the dense conditions inside salmon cages and can spread to juvenile wild salmon migrating past the farms. Mechanical treatments used to remove sea lice from farmed fish often return the parasites to the surrounding water. Disease transmission also occurs through biological waste discharged during fish processing or net cleaning, which can spread viral infections to wild fish populations. These risks were a central factor in British Columbia’s recent decision to phase out open net-pen salmon farming in its waters.
Pond-based shrimp farming in tropical regions has its own legacy of environmental damage, particularly the destruction of coastal mangrove forests to build farm sites. Mangroves serve as nursery habitat for wild fish and as buffers against storms, so their loss has ripple effects far beyond the farm itself. In contrast, shellfish farming (oysters, mussels, clams) is generally considered one of the most environmentally benign forms of aquaculture because the animals filter water as they feed, requiring no added feed at all.
Certification and Standards
Several certification programs exist to help consumers identify responsibly farmed seafood. The Aquaculture Stewardship Council (ASC) is one of the most widely recognized, setting requirements that cover environmental stewardship, animal welfare, human rights on farms, and farm management practices. ASC’s chain-of-custody program also includes requirements around food safety and antibiotic detection, meaning certified products must demonstrate that antibiotics haven’t been used outside of approved guidelines.
Best Aquaculture Practices (BAP) certification operates on a similar model. Both labels appear on packaging in major grocery chains. While no certification system is perfect, these programs give consumers a practical way to distinguish between operations with third-party oversight and those without it.
Why It Keeps Growing
Wild-catch fisheries have been essentially flat since the late 1980s, producing around 92 million tonnes in 2022. The oceans are, for the most part, already fished at or beyond sustainable limits. Meanwhile, global demand for seafood continues to rise with population growth and increasing incomes in Asia and Africa. Aquaculture is the only way that gap gets filled. The total aquaculture harvest in 2022, including seaweed, reached 130.9 million tonnes, a record. That trajectory is expected to continue, with nearly all growth in global seafood supply over the next decade projected to come from farming rather than fishing.