Brown trout and Atlantic salmon are closely related and they share a similar life history in their native waters. Both are also storied fishing targets that have inspired anglers for centuries, first in Europe, where both fish are native, and now all over the world where they’ve been introduced.
I remember standing above a little pool on an Adirondack creek in upstate New York, a palm-sized fish cradled in my hand.
“Look at the colors on this little brown,” I remarked to my fishing partner for the day, a native of the area who had agreed to take me out fishing for an afternoon. “Just gorgeous.”
My friend wandered over, and, just as I was about to release the 8-inch-long fish, he said something that surprised me.
“You can now tell anyone who asks that you’ve caught an Atlantic salmon.”
Come again?
I looked closer at the little fish, and, for the life of me, I couldn’t figure out how this obvious wild brown trout, eking out a living in this little trickle high in the mountains, could be mistaken for a salmon. But he was the expert, so I demurred.
“How can you tell?” I asked. And that’s where things get interesting.
Unique life histories
Atlantic salmon and brown trout are the fishy equivalent of first cousins. Both are native to the shores of Europe (and the salmon range west to North America, too), and both are prominent members of the Salmonidae family, which includes all trout, char and salmon.
But browns and Atlantic salmon are more closely related to each other than they are to other salmonids. In many places in northern Europe, the two fish share the same habitat and swim alongside one another.
Even though they’re subtle, there are differences between the two subspecies. As I noted, when they’re smaller, they’re very difficult to tell apart. As they get older and bigger, and their life histories diverge a bit, it gets easier.
Brown trout
Browns are true trout. Their taxonomic name, Salmo trutta, translates to “salmon trout,” which is a bit redundant. But it makes sense. Browns are native to Europe and the Atlas mountains of north Africa, and they thrive in cold and cool waters, even if those waters don’t have an immediate connection to the sea.
Does that mean browns can’t tolerate salt water? Absolutely not. In fact, in many northern and western European river drainages with immediate connections to the Atlantic Ocean, browns use the near-shore waters to grow big and fat in the salt over the course of summer. They only return to the freshwater in the fall to spawn and overwinter.
These sea-run brown trout are simply called “sea trout,” and this is likely where the bulk of the confusion is introduced when it comes to their similarities with Atlantic salmon.
Atlantic salmon
Considered by many to be the ultimate coldwater game fish, Atlantic salmon are bona fide anadromous fish, meaning that they spend most of their lives at sea and only return to freshwater in the summer and fall to spawn.
Just as browns are true trout, the high-flying Salmo salar (which translates as “leaping salmon” from Latin) are true salmon. Where browns might spend anywhere from a few weeks to a few months prowling the sea, Atlantic salmon range far and wide, and spend most of the year in the salt.
Some Atlantic salmon that have been caught in places like Scotland have been found to range as far as Greenland and even off the coast of Newfoundland, Labrador and the United States. Conversely, salmon that spawn in North American waters range as far as Scandinavia and even far western Russia.
Some Atlantic salmon even run into the rivers and streams of Hudson Bay in northern Canada, which means they come very close to using the waters of the Arctic Ocean.
Oddly, just as browns can move in and out of saltwater, Atlantic salmon can live their entire lives in freshwater. These are called landlocked Atlantic salmon, The fish I caught in upstate New York was a landlocked salmon.
Appearance
As fry and parr (juvenile fish), the two fish are virtually identical. As they grow older, there are some differences in features you can use to tell the two fish apart.
First, look at the caudal fin, or tail. As they get bigger, Atlantic salmon will display a slightly forked tail. If you look at the tail of a brown trout, you’ll notice it’s squared off.
Another way to tell the two apart is to look at the fish’s teeth. Browns actually teeth in the roofs of their mouths, called Vomerine teeth. They’re well-developed and the fish use them. Atlantic salmon also have Vomerine teeth, but they don’t have as many, and they don’t seem to use them.
Also, the jawline of brown trout will extend past its eye. The jawline of an Atlantic salmon will not.
Many biologists believe that the lack of Vomerine teeth and the position of the jawline are ways the two fish have evolved differently over eons.
Behavior
Both fish are very aggressive, and both fish eat everything from insects and worms to other fish. Atlantic salmon, though, because they spend more time at sea, also eat shrimp, krill and oceanic baitfish. But when they come home to spawn, anglers usually chase them with fly rods and use very subtle flies that swing on or just under the surface.
The brutal attacks on flies and the tendency to leap from the water time again once hooked is likely why anglers the world over love the Atlantic salmon.
Browns, too, will hit dry flies. But you can have success catching brown trout with lures, bait and flies. In the fall, as browns migrate to spawn, they are very aggressive, and many fly fishers will go after them with streamers.
Final thoughts
Brown trout and Atlantic salmon both occupy regal seats among the salmonid monarchy. Both are highly sought-after game fish, and they’re cherished by anglers all over the world.
But brown trout are primarily freshwater fish (although some run to the ocean and back if they live near the sea), while Atlantic salmon spend most of their lives in the ocean and only return to freshwater to spawn.
They are very closely related, but there are some differences you can use to tell them apart. The most obvious differences are in the tail and the teeth.
Regardless, both fish are prized for their craftiness and for how hard they fight once they’re on the line.
FAQs:
They are both members of the Salmonidae family. Brown trout (salmo trutta) and Atlantic salmon, (salmo salar) can look a lot alike, particularly when they’re both in freshwater. The two fish are very closely related, and some anglers mistakenly identify one as the other.
How can you tell them apart?
Brown trout have square tails and Atlantic salmon have slightly forked tails. Also, the jawline of a brown trout will extend past its eye. And Atlantic salmon’s jawline will not.
Where are they found?
Today, brown trout are found on every continent except Antarctica. They’ve been transplanted from the native Europe to coldwater habitats all over the world. Atlantic salmon were once only found in the cold waters of the north Atlantic Ocean. They are now farmed as food fish in cold ocean habitats all over the world.
Are brown trout as good to eat as Atlantic salmon?
Certainly, sea-run brown trout, or just sea trout, have many of the same characteristics of Atlantic salmon when it comes to their culinary assets. But, generally speaking, Atlantic salmon are much better table fare.
