Effluent from aquaculture operations — nutrients, chemicals, and pathogens — degrades water quality for wild fish. Improved effluent treatment protects both farmed and wild fish welfare.
Aquaculture effluent is an invisible welfare threat to the millions of wild fish living in or downstream of farming operations. Hypoxic zones created by nutrient enrichment cause slow suffocation for fish unable to escape — one of the most distressing forms of aquatic welfare failure. Antibiotic-resistant bacteria created by antibiotic discharge affect the health of wild fish communities. Chemical treatments for sea lice damage non-target invertebrates including crustaceans. The most effective welfare intervention is transitioning to closed-containment systems that treat effluent before discharge. In the interim, stricter siting regulations, mandatory effluent monitoring, and incentives for IMTA and RAS adoption reduce harm to wild aquatic communities.