Yes, all members of the order Salmonidae, which includes trout, have jaws and teeth. They have a lower jaw called a mandible and an upper jaw called a maxillary. Trout have teeth on both jaws, and teeth on the tops of their mouths!
When I was a kid and went fishing with my grandfather in Colorado’s high country, we’d catch a lot of trout. We caught rainbow and brown trout, but mostly we caught brook trout.
Every time we’d catch a fish that we intended to harvest, my grandfather would almost immediately kill and gut the trout before he put it in his creel. I was fascinated by the process.
As I helped him clean the fish on the stream bank, I was most fascinated by the fish’s jaws and the rows of tiny teeth each fish possessed. I wondered what purpose those teeth served.
Now, decades later, as a die-hard fly fisher, I know how trout use their subtle, yet quite sharp teeth. From birth to death, trout are carnivores, and their jaws and teeth have evolved over time to give trout the ability to bite and grip their prey.
Trout eat everything from very small insects and insect larvae to mice and even frogs. The taimen, the largest trout in the world, eats large rodents. Even brown trout, rainbow trout and cutthroat trout eat mice.
The trout’s jaws make a lifetime of eating protein possible
The bottom jaw of the trout is the “movable” jaw. Called the mandible, it’s the half of the jaw that opens and closes. When you see a trout holding in clear water, its jaws open and close as it pushes water through its gills to pull oxygen from the water. It’s the mandible that you see opening and closing.
Next time you catch a trout, carefully put your index finger on its lower lip and lightly push down. The jaw will open. And, you’ll see the trout’s teeth. If you try to push the upper jaw — the maxillary — up, it won’t move. It’s fixed in place. Only the mandible moves.
So, when a trout goes to eat something, it’s the mandible that opens up the fish’s mouth. If you watch rising trout, you can eventually see the bottom half of the trout’s jaws open and close when they grab insects off the surface.
Trout Have Teeth … and a Tongue, Too
The trout’s jaws are just part of what helps the fish bite its food. Both the mandible and the maxillary have rows of small, yet sharp, teeth. But trout also have teeth on the roofs of their mouths.
These teeth are called vomerine teeth, and they work with the trout’s tongue to manipulate food once it’s in the trout’s mouth.
The trout doesn’t have molars, incisors or giant fangs. Instead, most of their teeth resemble canine teeth. These teeth grab and hold prey, while the vomerine teeth work with the trout’s tongue to move the food around and make it easier for the fish to swallow.
Can You Hold a Trout by Its Jaws?
You can hold a trout by its lower jaw — the mandible — but it’s best not to. Trout, while resilient and very effective predators, can be a bit fragile. If you plan to release a trout, don’t “lip” it or “mouth it.”
And, if it’s a larger trout, I wouldn’t recommend grabbing it by the jaws. Larger fish have larger teeth, and they are sharp enough to rake across the skin of your thumb.
You may not feel the small injury at first, but in time, you will. Trout mouths, just like any fish’s mouth, contain bacteria, and the wound can become infected.
Mostly, though, it’s better to hold trout under their bellies. Their bones are made of cartilage, and they’re not accustomed to supporting the fish’s weight outside of the water. If trout start to wriggle and struggle, you can turn them carefully upside down, and they’ll calm down.
All trout are predators. They use their jaws and teeth to bite and grab their prey.
Trout have both upper (maxillary) and lower (mandible) jaws. Both jaws are lined with teeth, but only the lower jaw opens and closes.
It’s best not to “lip” or “mouth” a trout. First, bigger fish have bigger teeth. Those teeth are capable of breaking your skin. If the water you’re fishing in or slime from the trout contains bacteria, the minor wound can get infected.
The best way to hold a trout is from underneath. Don’t squeeze it. Just cradle it. Then, you can remove the hook and release the fish unharmed.
Can You Lip Other Fish Besides Trout?
Yes. Many anglers lip bass and panfish, like crappie or bluegill. Be careful, though, because lifting any fish by its jaws puts undue pressure on the fish’s fragile cartilage bone structure.
Are Some Trout Better to Lip or Mouth Than Others?
No. As a general rule, it’s best not to lip any trout, especially if you plan to release the fish alive.
Will Trout Bite You When You Take Them Out of the Water?
No. Trout will not bite you when you remove it from the water. Some fish, like needlefish, for example, will absolutely bite you!