Are Salmon Freshwater or Saltwater Fish?

There isn’t a difference between freshwater salmon and saltwater salmon, as they’re the same species. So, when you’re trying to identify whether you’re looking at a salmon freshwater or saltwater “species,” you need to know where the salmon spent its adulthood. 

The Nuances of Freshwater and Saltwater Salmon Habitats

It’s important to explore the question, “Where do salmon live?” to understand how freshwater and saltwater salmon get their labels.

Salmon are anadromous, meaning they spend a portion of their lives in the ocean and freshwater. To be more precise, they’re born in freshwater, move to the ocean, and then return to freshwater to spawn. The length of time a salmon spends in the freshwater after they’re born depends on the species.

That said, not all salmon make it to the ocean. Instead, after a salmon is born, natural obstructions like waterfalls and human obstructions like dams can prevent them from reaching the sea. 

In these cases, salmon remain a strictly freshwater species, treating lakes as their “ocean” and using streams or rivers to spawn as they normally would.

How Can Salmon Live in Freshwater and Saltwater?

Non-anadromous fish would die by moving between freshwater and saltwater. However, salmon can do this because they have the ability to regulate sodium by moving it into and out of their bodies.

When they’re born in freshwater, salmon increase their body’s sodium intake by using molecular pumps. They then remove excess sodium when they transition to saltwater to maintain the balance of sodium in their bodies. 

Once salmon return to freshwater, their molecular pumps reverse, drawing in higher concentrations of sodium to maintain equilibrium.

Understanding Salmon Names

Many people refer to salmon that can’t access the ocean after they’re born as “landlocked.” They also sometimes go by “landlocked Atlantic salmon,” helping people recognize that they’re the same species as the standard Atlantic salmon.

Other times, you’ll hear these landlocked salmon called “freshwater salmon.” However, don’t let this terminology confuse you—even landlocked salmon remain anadromous, with the ability to thrive in the ocean should they ever regain access to it.

Are Freshwater Salmon and Saltwater Salmon the Same?

You might see other name variations between landlocked salmon and those that spend time in the ocean, such as with the Sockeye salmon. When caught in the ocean, fish markets often label these fish as Sockeye salmon. However, they usually use the term Kokanee salmon to refer to the landlocked version of this same species.

In contrast, the following species of salmon usually don’t change names regardless of whether they’re landlocked or spend time in the ocean:

  • Coho salmon
  • Chinook salmon

Physical Differences Between Freshwater and Saltwater Salmon

Even though they’re the same species, a saltwater salmon often looks different from its freshwater version. These fish usually appear the healthiest in saltwater, and they typically have a brilliant silver to blue-like body color. They also often have black spots on their bodies with a back that’s darker in color.

Upon entering freshwater, a male salmon’s back often becomes humped, and it develops a hooked jaw appearance.

Regardless of gender, most salmon bodies change color upon arriving in freshwater. They also usually lose their black spots, except Chinook and Atlantic salmon. 

Often, Sockeye salmon will turn a beautiful bright red color in freshwater. They do this to catch the eye of female Sokeyes for mating. In contrast, King salmon turn dark with a deep blackish brown color.

Meanwhile, the seven Pacific salmon species become thin and sickly looking as they make their way from the ocean up freshwater streams. They even lose flesh along the way, which is most notable around their gums, making them look more “teethy” than when they’re in the ocean.

Eating Behaviors of Freshwater vs. Saltwater Salmon

If you’re wondering whether salmon freshwater or saltwater varieties eat better, the answer is that they almost always eat better when they’re in saltwater.

When they’re in the ocean, salmon have an array of meal options, including:

  • Crustaceans
  • Fish
  • Squid
  • Octopus
  • Polychaete worms

In contrast, freshwater salmon often rely on a combination of insects and aquatic life to meet their nutritional needs. Examples include:

  • Blackflies
  • Caddisflies
  • Riffle beetles
  • Small amphibians
  • Fish

However, there are some caveats to consider when looking at the eating habits of freshwater salmon. For starters, all salmon begin their lives in freshwater. During this time, they’ll eat the foods described above.

Should these young salmon become landlocked, they have no choice but to feed on these same foods for the rest of their lives.

In contrast, saltwater salmon typically eat little to no food during their journey from the ocean into freshwater. Nevertheless, although anorexia is common among these migratory saltwater fish, fisherpeople have found occasional food in these salmon’s stomachs.  

How Freshwater and Saltwater Salmon Differ in Behavior

Although freshwater and saltwater salmon are the same species, they may display different behaviors depending on their environment.

For example, landlocked freshwater salmon will make their way from the freshwater river or stream where they’re born to the deeper waters of a lake. There, they try to mimic the lives they’d live in the ocean.

In contrast, saltwater salmon move to the ocean to live their adult lives until they reach sexual maturity. During this time, they’re at their maximum health. However, once they re-enter freshwater to spawn, their health usually deteriorates.  

How Long Salmon Spend in Freshwater

All salmon are born freshwater fish, but the length of time they stay there varies between species before attempting to make their way to the ocean. It goes as follows:

  • Pink and Chum: Leave immediately
  • King (Chinook): Up to five months
  • Coho: Up to one year
  • Sockeye: 1 – 4 years
  • Atlantic: 2 – 3 years

A Note on Fishing Laws

Whether you’re doing salmon freshwater or saltwater fishing, it’s crucial to follow local laws about when it’s safe to fish for these species and the size range you’re allowed to keep. 

That way, you’ll help contribute to sustainability so that this species can continue going through their freshwater and saltwater life cycles.

So Are Salmon Fresh or Saltwater Fish?

I think by now we can all agree that the answer is… BOTH! They are incredibly versatile animals who have found a unique way to adapt to their unique circumstances. Or as Ian Malcom said in Jurassic Park, “Life finds a way.”

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