If you're devoted to the pursuit of trout or raise trout for food, knowing the sex or gender of a trout is important to you. It can be hard to distinguish males from females, as many trout species look alike. For some trout species, it's easy to figure out the gender by visual recognizing characteristic such as color patterns, size and specific body parts such as jaw and gills, fins and belly. For others, watching trout behavior will help you in determining gender.
Identify a trout’s color patterns to find out its sex. Look for discrepancy and different markings within a single species. For instance, both male and female rainbow trout have bright reddish streak running from their gills to tail. However, male rainbows have a notable feature that distinguishes them from females. An older adult has hook jaws that grow in adults after 2 years. Additionally, male rainbows turn brick red as they mature. Female rainbow trout have narrow jaws and the red streak turns more pinkish than red, during spawning.
Examine a trout's gills and fins; look for noticeable colors and unusual thickness. In male cutthroat trout, red to yellow streaks cover the gills and underside near the jaw. The bright red streak under the gills gives the appearance that the fish has been injured and is bleeding. A female doesn’t have this red mark. On brown trout, for instance, you can identify female from a male by looking at the thick anal fins of the fish. Females normally have 9-12 rays, which get noticeably thicker during the breeding season. Males have less than 9 rays and they don’t become as thick when its time to spawn. Additionally, male browns have a profound upper hook jaw that extends from the tip of the trout’s mouth to the head.
Determine a trout's gender by its size. Attempting to gauge the size of a trout while it is in the water can be difficult, as water often distorts the true size of a fish. However, when caught, you can measure the size and compare the fish against others. In most trout species, female trout are larger than males, not only in size but also in their weight. A clear example would be in brook trout. An adult female brook trout generally grows a foot long and weighs 1-2 pounds. The opposite is true when it comes to a male adult brook trout. They normally measure less than 8 inches and weigh a pound or less, according to the Maryland Department of Natural Resources website.
Watch the behavior of trout within the water. How a trout acts is a strong indication of whether it's a male or female. Here is an example, wild brook trout found in streams in Virginia, West Virginia and Maryland, build gravel nests within shallow spots to spawn. Females kick out gravel with their tails and huddle down over top of the dug out area to lay their eggs. Males move alongside the females and start secreting semen onto top of the eggs. After the process is complete, the males will stand watch over the nests, protecting the eggs until the fish hatch. In river and streams, you can spot the male, as it sways back and forth not far from where the eggs lay.
Observe trout for pregnancy. When you catch a fish, physical observe its belly. Only females carry eggs, and seeing a big belly trout can alert you that the trout is female. Visit a commercial trout farm during the spring. You can visually observe female rainbows, brooks and browns that are pregnant. The farm employees, in most cases, will pull the fish from the water and allow you to gently rub your hand over the stomachs of these bloated fish. You may get to actually observe a female release her eggs from out of her body, while you gently run your hand down the stomach of the trout.