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. 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. aquaculture climate change
In Bangladesh, the world’s fifth-largest aquaculture producer, sea-level rise threatens 50% of the coastal shrimp and prawn farms. Saltwater intrusion also contaminates freshwater aquifers used for hatcheries and processing. Farmers face a cruel irony: shrimp farming requires brackish water, but the precise salinity tolerance of black tiger shrimp (15-25 ppt) is narrow; too much freshwater from upstream dams, or too much salt from sea intrusion, both cause mortality. Climate change intensifies the hydrologic cycle, producing more frequent and severe cyclones, floods, and droughts. For aquaculture, which requires stable water quality and physical infrastructure, extreme weather is an immediate, destructive hammer. In Norway and Scotland, Atlantic salmon farmers have