This comment and remark are related to the article of Kovalevsky V. “Selecting females for certain, better color“.

Methyltestosterone

hormones are so effective at causing the sex changes in fish that some fish farms in both the U.S. and abroad intentionally feed with this compound to their fish (usually tilapia) to prevent breeding by turning all of their fish into males. This helps farmers control populations, and divert the energy the fish would use for breeding to growing more tissue, producing a larger animal.