Also known as sexual dimorphism — luckily no forest fire risk with this reveal

The alevin are looking great and we only need about 291 more names. But, “Are they males or females?” asks Elanor the Animal Expert (age 7) from The Bronx. Thanks for the great question, Elanor. While “gender reveal parties” are the new fad, these trout will display sexual dimorphism over time.

Although we can’t tell the difference between the male and female alevin, trout do show male or female characteristics as early as one-year after hatching. By age two most trout display sexual dimorphism and males can be differentiated from females. One way to tell the difference is by looking for a kype (hook-like distal tip of the lower jaw) another is to look at the coloration on the trout’s belly. The kype develops in males and with their sharp teeth they can defend their territory, in a stream, from other males. Male trout also develop brighter colors during the spawning season.

How to tell them apart.

Science Journal Question for TIC Students: What other animal species have males and females that look different from one another? Which of the two have the brighter colors and why?

Dive Even Deeper: What are the differences between the male and female adult brown trout in the photo above? (hint: there are more than just two!) How do the different characteristics of male and female trout contribute to the survival of these species?