Aquaculture, the practice of farming aquatic organisms such as fish, shellfish, and aquatic plants, contrasts with wild-capture fisheries, which rely on harvesting naturally occurring stocks. The rise of aquaculture has profoundly reshaped the global seafood landscape. Its interaction with wild seafood catch reveals a complex dual influence, offering a necessary supply solution while creating new environmental and ecological challenges for wild populations. Understanding this interaction is central to the future sustainability of the world’s aquatic food resources.
The Quantitative Shift in Global Seafood Supply
The sheer volume of farmed production has fundamentally altered the source of the world’s seafood. Aquaculture has expanded rapidly, moving from a marginal contributor to a dominant global food source. For the first time, aquaculture has surpassed wild capture as the primary source of aquatic animal products for human consumption.
In 2022, aquaculture provided approximately 57% of the aquatic animal food consumed globally. Wild-capture fisheries production has stabilized since the 1990s, hovering near 90 million tonnes annually. The total increase in global seafood availability is almost entirely attributable to farmed production, establishing aquaculture as the main driver of global seafood supply.
Aquaculture as a Market Stabilizer
The massive volume of farmed fish acts as an economic buffer, stabilizing markets and reducing fishing pressure on certain wild populations. By providing a consistent, high-volume supply of popular species, aquaculture introduces a substitution effect. Consumers are presented with a more affordable and readily available farmed alternative, dampening the economic incentive to intensively fish wild counterparts.
The market introduction of farmed salmon, tilapia, and catfish has lowered their overall price points. Without this farmed supply, growing global demand would fall entirely onto wild stocks, accelerating the overexploitation of stressed fisheries. This mechanism helps distribute consumer demand across a broader range of sources, slowing the rate of decline for some commercially valuable wild stocks. However, some analyses suggest that aquaculture has increased the overall market for seafood rather than substantially displacing wild fishing, preventing a significant reduction in total wild catch effort.
The Demand for Wild Resources in Farm Feed
The farming of carnivorous species creates intense, indirect pressure on wild populations through feed requirements. Species like farmed salmon, shrimp, and tuna require diets rich in protein and oils, historically sourced from Fishmeal and Fish Oil (FMFO). FMFO is produced by “reduction fisheries” that catch small, oily forage fish such as anchovies, sardines, and menhaden. This practice removes organisms from the base of the marine food web, which are food sources for larger wild predators, seabirds, and marine mammals.
The ecological cost is measured by the Fish In:Fish Out (FIFO) ratio, which calculates the weight of wild fish needed to produce one unit of farmed fish. While early FIFO ratios for species like salmon were high (e.g., nearly 5:1), industry improvements have significantly reduced this reliance. The global average FIFO for all fed aquaculture is now well below 1:1, meaning the sector produces more farmed fish than it consumes as wild-caught feed. This improvement is driven by a greater reliance on plant-based proteins, like soy, and novel ingredients such as algae oils and insect-based meals.
Ecological and Environmental Spillover Effects
Aquaculture operations impact wild catch by directly affecting the shared aquatic environment. A primary concern is the transfer of disease and parasites from densely populated farm pens to passing wild fish populations. Pathogens and parasites, such as sea lice, can proliferate in open-net salmon farms and infect vulnerable wild salmon populations, reducing their fitness and survival rates.
Habitat modification is another consequence, particularly in coastal areas. The construction of shrimp farms, for instance, has historically led to the destruction of critical coastal ecosystems like mangrove forests. Mangroves serve as nurseries and breeding grounds for numerous commercially important wild fish and shellfish species. The loss of this habitat disrupts the reproductive cycle of wild stocks, leading to population declines.
The escape of farmed fish introduces a risk of genetic mixing with native stocks. Farmed fish are often selectively bred for traits like fast growth, making them genetically distinct from their wild counterparts. When these domesticated escapees interbreed with wild populations, the resulting offspring may have reduced survival and reproductive success. This genetic dilution weakens the overall fitness and resilience of the wild stock, posing a long-term threat to local wild fisheries.