Nile tilapia (Oreochromis niloticus) dominate global production. Tilapia are hardy, fast-growing omnivores suited to intensive production in tropical and subtropical regions. Major producers include China, Egypt, Indonesia, and Bangladesh. Production systems range from extensive ponds to intensive recirculating aquaculture systems (RAS).
Tilapia are territorial and aggressive, particularly males during breeding season. High stocking density (above 50-100 fish/m³ in intensive systems) causes chronic stress from crowding and competition. All-male monoculture (achieved through sex reversal with methyltestosterone or through selective breeding) reduces reproductive aggression in production settings.
Tilapia tolerate lower dissolved oxygen than many fish species but still experience welfare-relevant hypoxia below 3 mg/L. In pond systems, algal blooms cause oxygen crashes that can kill thousands of fish. Aeration management and algal control are welfare-critical interventions. High ammonia from intensive feeding reduces immune function and growth.
Tilapia are affected by streptococcosis (Streptococcus agalactiae), major lethal disease causing neurological signs and mortality; columnaris (Flavobacterium columnare); and tilapia lake virus (TiLV), an emerging threat. Disease causes significant welfare harm through pain, behavioral abnormality, and death. Vaccination programs for streptococcosis are increasingly used in large-scale operations.
Tilapia are commonly harvested by seining, crowding, and direct icing — a method that causes a slow death over minutes to hours at declining temperatures. Percussive stunning followed by gill cutting provides a significantly more welfare-positive end to life. The Aquaculture Stewardship Council (ASC) is developing tilapia-specific slaughter welfare standards.
Sex reversal of tilapia using methyltestosterone (a synthetic androgen) produces all-male populations for production. Welfare concerns about hormonal treatment of fish during critical developmental periods are raised but poorly studied. Genetic male tilapia (GMT) produced through selective breeding of feminized males provides an alternative to hormone treatment with comparable production advantages.