How to Tell the Difference Between a Male and a Female Fish
It can be quite difficult to determine the sex of a fish. Scrutiny of a few general features, however, can sometimes point you in the right direction. It's advisable, if you're truly interested, to seek out more detailed information on a given species; if distinguishing features exist, they may be very subtle and technical.
Other People Are Reading
Instructions
-
-
1
Look at the fish's coloration. In some cases, one sex is more brightly or intricately patterned than the other. The stripes of the female maroon clownfish are grayish, for example, while those of the more striking male are white. Male and female bluehead wrasses exhibit complex color variations that vary depending on sex and size class. Keep in mind that coloration in some fish changes during the breeding season.
-
2
Consider other morphological differences. Male sharks have claspers, which are modified fins that assist in reproduction. They are usually quite obvious, trailing behind the shark's pelvic fins; females lack them. In the threespine stickleback, the males often have larger heads and mouths; females are usually longer with lengthier pelvic girdles. Typically, male plains minnows (at least in Texas's Brazos River) have longer first dorsal rays than females, in addition to bigger heads. And the leading edge of the bonnethead shark's eponymous feature---it is a small member of the famous hammerhead family---is more convex in the male.
-
-
3
Estimate the fish's size. In many species, females are larger. Deep-sea anglerfish exhibit some of the most extreme sexual dimorphism among fishes; females are often mammoth in proportion to their male counterparts.
-
4
Watch behavior. In some cases, observing fish activity during the breeding season---mating, egg-laying or live-young rearing, etc.---is the only easy way to distinguish sexes.
-
1
