Aquaculture and Ecosystem Impacts: Welfare Beyond the Farm

Fish farming affects not only farmed animals but wild species through pollution, disease transmission, and wild-caught feed requirements. Understanding these ecosystem welfare impacts completes the aquaculture welfare picture.

Key Facts

Sea cage salmon farming releases nutrient-rich waste that causes benthic habitat destruction beneath and around farm sites
Sea lice from salmon farms transmit to wild juvenile salmon migrating past farm sites, causing significant wild fish mortality
Approximately 20% of global wild fish catch is reduced to fishmeal and fish oil for aquaculture feed, affecting marine food webs
The feed conversion ratio of salmon is approximately 1.1-1.2 kg of feed per kg of fish produced, among the best of any farmed animal
Escaped farmed salmon interbreed with and displace wild populations in Atlantic rivers where they were historically native
Recirculating aquaculture systems (RAS) eliminate most ecosystem impacts by treating waste and preventing escapes
Closed containment systems significantly reduce sea lice transmission and nutrient release compared to open sea cages
Certification schemes addressing ecosystem impacts have limitations in capturing all welfare-relevant consequences for wild animals

Welfare Considerations

The welfare story of fish farming is incomplete without accounting for the wild animals affected by farm operations. Sea lice infestations transmitted to wild juvenile salmon cause welfare harms and population declines that extend far beyond the farm boundary. Wild fish caught for aquaculture feed experience their own harvesting welfare harms. Escaped farmed fish compete with wild conspecifics. The welfare case for aquaculture system improvements — closed containment, RAS, improved feed ingredients — is strengthened when these ecosystem welfare externalities are included in the calculation alongside direct farm animal welfare.

What You Can Do

Choose certified sustainable aquaculture products from closed containment or RAS systems where available
Support policy requirements for closed containment systems in ecologically sensitive salmon farming locations
Advocate for feed ingredient standards that reduce reliance on wild-caught fish in aquaculture diets
Support research on plant-based and insect-based aquaculture feed alternatives that reduce wild fish harvest
Engage with aquaculture certification bodies to ensure ecosystem welfare impacts are included in standards
Reduce consumption of farmed salmon from open-net cage systems where ecosystem impacts are most significant