“The consequences of these MMEs [mass mortality events (of farmed fish)] are not limited to the stock of salmon but can have significant impacts to the surrounding environment (through nutrient release and the creation of anoxic “dead zones”) and the people working in the aquaculture production facilities, and the consequences tend to worsen with increased magnitude of MMEs.”
7 March 2024 Nature (Nature is the world's leading multidisciplinary science journal)
“Significant emissions of dissolved nitrogen compounds, of which there is normally too little in the summer, can lead to increased phytoplankton production, increased breakdown of algal biomass in the depths and lack of oxygen in the bottom water, as well as changes in macroalgal communities in shallow water. We call this condition eutrophy. Overfertilization leads to increased biomass production that disrupts the natural ecological balance in the coastal zone, with serious detrimental consequences for biodiversity, ecosystem resilience, recreational activities and fishing.” Quote from the Risk Report Norwegian fish farming 2024 by the Norwegian Institute of Marine Research

Watch footage showing the dead seabed under the fish farm at Musholm, Denmark, at minutes 2:20 and 2:39.
Watch footage of dead zones under Faroese salmon pens at minutes 2:45, 6:02, 6:41 and 53:28 in the Faroese documentary Undir laksin (Under the Salmon).
● Watch footage showing anaerobic bacterial mat covering the sea floor at 300 m depth under a salmon farm in Osterøyfjorden near Bergen, Norway
● Watch footage showing anaerobic bacterial mat covering the sea floor at 40 m depth under a salmon farm in Bømlo and at 170 m depth under a salmon farm in Holevik, Norway
● Watch footage from under Norwegian salmon farms at various depths
Watch footage that compares a healthy seabed in Iceland with one that has been smothered under salmon farm pens
Watch footage of the bacterial mat under a salmon farm in Iceland
● Watch footage showing dead zones under open-pen salmon farms in Kawésqar National Reserve
● Watch footage showing a dead zone under a salmon farm in Chile
● Watch footage showing smothered marine fauna near salmon farms off Huon Island
● Watch footage showing dead zones under salmon pens in the Tasmanian documentary Paradise Lost by Justin Kurzel and Conor Castles-Lynch
Watch footage showing a dead zone under Scottish salmon farms
Watch footage of bacterial mat under a Scottish salmon farm

● Marine ecologist Dr Sally Campbell says: "I think most people who choose salmon off their supermarket shelves have no idea of the waste that's going into our marine environment as a result of that. And they would be appalled." Reference
● “Today, the EPA made public a report cited by Four Corners on Monday which revealed all marine fauna for at least 500 metres around a Tassal salmon lease close to the World Heritage Area was dead.” Reference
● “A group of some of Australia’s leading scientists this week urged the federal environment minister, Tanya Plibersek, to remove fish farms from the harbour to save the skate population, which fell sharply last decade as salmon stocks increased and dissolved oxygen (the amount of oxygen present in water) levels fell.” Reference
“Oxygen-poor [Chilean] fjords and rotting salmon triggered a huge algae bloom in the area, which poisoned the sea and killed almost all marine life. After this crisis, the salmon industry realized it was time to find cooler and cleaner seas to frolic in - and began its expansion south.” Reference

Anoxic (“dead”) seabeds due to open-pen salmon farming