It is usually difficult to visually identify the sex of a fish by its external physical features. Fish that do exhibit sexual dimorphism (physical differences between males and females) usually do not develop distinguishing features until adulthood or during mating season. The most reliable way to determine the sex of a fish is through dissection or genetic testing.
How can you tell if a fish is boy?
Fish do not have gender in the same way that humans do. They have sexes, as they can be either male or female, meaning they have either male sex organs (testes) and produce sperm or female sex organs (ovaries) and produce eggs. During spawning season, male fish may develop differences in coloration or body shape known as secondary sexual characteristics, but this is not a foolproof way to determine the gender as these characteristics can vary between species and individuals.