How To Tell If A Trout is Male or Female

This is a guide to the best ways to distinguish the sex of a trout and the differences between male and female trout.

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In this article, we’ll look at the differences between male and female trout. It’s one of those topics that spark a lot of conversation on the water. I’ve caught a good number of trout in my fly fishing career and, when I started out, I couldn’t figure out how to tell male and female fish apart.

After reading up quite a lot and inspecting a ton of fish, I now know exactly what to look for and I’m going to be sharing the tips with you.

This article also falls into our fly fishing tips series where we look at techniques and tips that will not only make you a more successful angler but also teach you about fish and how amazing they are. Also, we have a video covering the same topic, be sure to check that out too.

General Comments Regarding Trout Gender

Before we dive into the differences between male and female trout, let me make a couple of general comments first, as it’s not always as easy as you’d think:

trout river fishing
  1. The differences we’re going to look at are mostly only applicable to sexually mature and active fish. If you caught a two inch fingerling, the chances are you won’t be able to establish what the gender is.

    You can always ask the fish, but once again, I’ve never met a trout that speaks human.

  2. The second point is that I’ve only seen the differences mentioned in this article in real life on brown trout and rainbow trout. Unfortunately, I do not stay on the right continent to go out on the water and see if this is true for other species like cutthroat or brook trout.

    My gut feeling is that they’re similar, but the one aspect I cannot confirm if the anal fin, which we’ll talk about later.

Watch the How Do You Tell if a Trout is Male or Female Video

YouTube video

What is the Difference Between a Male and Female Trout?

There are three ways to determine the sex of a trout. Not all of these characteristics might be visible all at once on the fish, so you’ll see only one or a combination of them.

The Jaw or Kype

The easiest and most accurate way to determine the gender of a trout is by looking at its jaw. A sexually mature cock fish develops what we call a kype. The bottom jaw extends past the top and forms an upward hook.

On female trout, also known as a hen, the kype is abesent and the bottom and top jaw are mostly the same length.

The Shape of the Anal Fin

In most cases, the anal fin of sexually mature cock and hen fish differ slightly, and it could be a subtle clue to the fish’s sex if the other characteristics are missing.

On cock fish, the anal fin is convex whereas, on female fish, the anal fin is concave. The difference might be slight and not easy to see if you only have one fish in your hand. The more trout you catch and inspect the better you’ll get at seeing the difference between male and female trout anal fin shapes.

Spawning Colours

A third method to determine the sex of a fish is coloring during the spawning season. In general, cock fish develop incredible rich and dark coloring when they’re preparing and busy spawning. In many cases, this goes hand in hand with the prominent kype that forms.


I hope that this video has shed some light for you on how to determine whether a trout is male or female. If you’re lucky, the cock fish in your area develop stricking colors and strong kypes, so differentiating them from females are easy.

Doesn’t matter what gender of trout you catch in the end, be sure to treat both of them with the same level of respect they deserve from us. Keep them wet and handle them as little as possible. Please subscribe to our channel and turn on the notifications, then we can let you know as soon as we release any future videos or tutorials.

Until next time!

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Pierre is a fly fishing guide and professional photographer who has guided and hosted trips for top fly fishing outfitters. Since being introduced to fly fishing over 21 years ago, he has travelled, fished and guided across the globe. He has extensive knowledge on specific gear and tackle selection for various salt- and freshwater species. Some of his writing work includes blogposts for Alphonse Fishing Company and African Waters.

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