Aquaculture Climate | Change

Mussels, clams, scallops, and abalone face identical threats. A 2020 meta-analysis of 150 studies found that larval bivalves exposed to projected 2100 pH levels showed 40% lower survival, 35% reduced growth, and significant shell malformations. For an industry built on high-volume, low-margin production, such losses are catastrophic. Most aquaculture infrastructure—ponds, cages, and processing facilities—occupies low-elevation coastal zones. The Mekong Delta, which produces 70% of Vietnam’s aquaculture output (including 1.6 million tons of pangasius catfish), sits just 0.5-2 meters above sea level. With global mean sea level projected to rise 0.5-1.2 meters by 2100—and storm surges adding 2-3 meters in extreme events—the delta faces inundation. Already, saltwater intrusion has advanced 20 kilometers up the Mekong River during dry seasons, salinizing freshwater ponds and killing catfish stocks.

Integrated multi-trophic aquaculture (IMTA) mimics natural ecosystems by farming fed species (fish or shrimp) alongside extractive species (seaweeds and bivalves) that absorb waste nutrients. Seaweeds, in particular, buffer pH locally through photosynthesis (which consumes CO2) and provide shelter from thermal stress. A Canadian IMTA farm producing salmon, blue mussels, and sugar kelp reported 15% higher salmon survival during a 2021 heatwave compared to monoculture neighbors, alongside a 40% reduction in waste nitrogen discharge. Beyond adaptation, the industry faces mounting pressure to reduce its own emissions. The most promising mitigation pathways transform aquaculture from a carbon source to a carbon sink. Seaweed Farming: The Blue Carbon Breakthrough Macroalgae aquaculture—farming kelp, nori, and other seaweeds—requires no feed, fertilizer, or freshwater. Seaweeds absorb CO2 directly from seawater through photosynthesis, and a portion of this carbon is sequestered when senescent biomass sinks to the deep ocean or is buried in sediments. Global seaweed farming currently covers 2 million hectares, producing 30 million wet tons annually. If expanded to 70 million hectares (0.5% of the ocean surface), seaweed farms could sequester 1 billion tons of CO2 per year—equivalent to Germany’s annual emissions. aquaculture climate change

In Norway and Scotland, Atlantic salmon farmers have experienced catastrophic mortality events during marine heatwaves. The 2019 event in Norway killed 10 million salmon—roughly 15% of the annual harvest—as temperatures exceeded 22°C, the species’ upper tolerance. Salmon cease feeding above 20°C, become immunocompromised, and succumb to sea lice and bacterial diseases. In warmer waters, metabolic rates accelerate, increasing oxygen demand while simultaneously reducing dissolved oxygen solubility. The result is a physiological vise: fish need more oxygen but have less available. Mussels, clams, scallops, and abalone face identical threats

The transition will not be easy or cheap. It requires phasing out $22 billion in harmful subsidies, enforcing mangrove moratoriums, and transferring technology to smallholders. It requires consumers to pay premium prices for climate-certified seafood and governments to enforce emissions disclosure. It requires a fundamental rethinking of what aquaculture means: not a extractive industry mining the ocean’s productivity, but a regenerative system enhancing ecological function while producing protein. Already, saltwater intrusion has advanced 20 kilometers up

Onshore recirculating aquaculture systems (RAS) represent the opposite extreme: complete environmental control. By filtering, sterilizing, and reusing 99% of water, RAS facilities can maintain optimal temperature and chemistry regardless of external conditions. Atlantic salmon grown in land-based RAS now achieve harvest sizes in 18 months versus 30 months in sea cages, with zero sea lice and no escapees. The catch? Energy intensity. RAS requires continuous pumping, aeration, and temperature control—energy demands 5-10 times higher than open systems. Unless powered by renewable energy, RAS exchanges climate vulnerability for a direct carbon footprint. Selective breeding and genetic modification offer pathways to thermal tolerance. The University of Stirling’s Aquaculture Genetics Group has produced tilapia strains that maintain feed conversion at 34°C, a 2°C improvement over wild-type. Norwegian salmon breeders have selected for heat shock protein expression, reducing mortality during marine heatwaves by 30% over five generations.

Offshore aquaculture—submersible cages placed 10-50 kilometers from shore in 50-100 meters of water—offers several climate advantages. Water temperatures fluctuate less, currents provide natural waste dispersal, and wave energy, while challenging, can be engineered around. Norway’s Ocean Farm 1, a 68-meter-high, 110-meter-wide submersible cage, survived winter storms that destroyed nearshore facilities. However, offshore systems require massive capital investment ($50-100 million per unit), sophisticated logistics, and confront unresolved legal questions in international waters.

The economic case is equally compelling. Seaweed extracts (carrageenan, agar, alginate) are used in everything from toothpaste to pharmaceuticals. Seaweed biofertilizers reduce methane emissions from rice paddies by 50%. And when fed to cattle, certain red seaweeds ( Asparagopsis taxiformis ) reduce enteric methane by 80%—a breakthrough for livestock emissions. The challenge is scaling production and harvesting without damaging benthic ecosystems. The single largest source of aquaculture emissions is feed production. Reducing the fishmeal and fish oil content of feeds—currently 10-15 million tons annually—would slash both direct emissions and pressure on wild forage stocks. Black soldier fly larvae, grown on agricultural waste, provide protein and lipid profiles nearly identical to fishmeal. Methane-oxidizing bacteria ( Methylococcus capsulatus ), fed natural gas, produce single-cell protein with a carbon footprint 90% lower than fishmeal. Fermented soybean and algal oils now replace 60% of fish oil in salmon feeds without compromising omega-3 content.