Sexing fish can be a very difficult task. While some fishes can be easily sexed, others are nearly impossible to distinguish between without cutting them open and examining their reproductive organs. Bass is a name shared by many different species of spiny-finned fishes belonging to the families Serranidae and Centrarchidae. There are various methods for determining the sex of bass, but there is no surefire method for determining their sex simply by physical appearance alone.
Step 1
Observe the fish during the spring. Spring is the breeding season, and mature female bass can be easily identified by their swollen or sunken abdomens. Their abdomens will either be swollen because they are full of eggs, or sunken because they have recently laid them.
Step 2
Determine the sex of larger bass (13 to 15 inches or longer) by examining the area around their urogenital opening. This is the opening on the rear underside of the fish. Females will have a circular scaleless area around their urogenital opening, while males’ scaleless area will be more oblong.
Step 3
Massage the abdomen of the fish by moving your fingers from the middle of the abdomen back toward the urogenital vent using gentle pressure. If milt (fish sperm) is expelled, then the fish is a male. If no milt is expelled, then the fish is likely a female, although not with certainty.