Why is tilapia farmed as all-male (monosex) stock?

Tilapia (Oreochromis spp.) start breeding within a few months. In mixed-sex ponds they reproduce heavily and uncontrollably, energy goes into breeding instead of growth, and the harvest is full of small fish. Males also grow clearly faster than females, which is why commercial farms prefer all-male (monosex) stock.

Common methods:

• Hormonal sex reversal: 17α-methyltestosterone in feed during the larval stage. Effective, but banned or restricted in some markets — check the buyer country's rules if you export.
• YY "supermale" broodstock: genetically produces nearly all-male offspring.
• Hybridisation: some crosses give a high share of males.
• Manual sexing: labour-intensive and error-prone.

Check your stocking plan with the stocking density calculator.