Why Do Salmon Swim Upstream? Nature’s Great Mystery

September 14, 2020

Why Do Salmon Swim Upstream? Nature’s Great Mystery

If you’ve gone fishing on the west coast of the united states, chances are you have heard of the salmon run. Each year, hundreds of thousands of salmon migrate from the ocean to small rivers inland. Many die on their way to their birthplace, and the lucky ones who make it die right after spawning. So why do salmon swim upstream anyways? Why do they risk their lives to lay their eggs in a small stream only to die afterward?

Salmon swim upstream to mate and lay their eggs for several reasons. Laying their eggs in small rivers and shallow waters help protect them from larger fish that would happily eat them as a snack in the ocean. The shallow streams and rivers also provide shelter for the eggs so they don’t get washed away by heavy currents. 

When the salmon eggs actually hatch, the fish fry (what small salmon are called) are also protected from predators. Small streams provide the perfect habitat for them to gain weight and get larger before heading out to the ocean. But there are so many other interesting facts to learn about why salmon swim upstream and their mating cycles. 

In this article, we’ll cover why salmon lay their eggs upstream, how it takes for salmon to swim upstream, and lots of other interesting information about salmon migration. We’ll also cover the different types of salmon there are, as well as how to catch salmon. Let’s jump in!

Why Do Salmon Lay Eggs Upstream?

As we mentioned earlier, the main reason why salmon lay their eggs upstream is to protect them. Salmon have learned that many more of their eggs will survive longer if they are in a habitat that protects them. 

The ocean is the exact opposite of this. If a salmon laid their eggs in the ocean, they would be swept out to sea or eaten by the thousands of other fish species they live with. Smaller rivers and streams don’t have these perils. Streams have weak currents and not many predators that eat salmon eggs.

It took many thousands of years for salmon to evolve and figure this out, but this is the main reason why salmon lay their eggs upstream. The salmon that started laying their eggs upstream began to outlive the salmon that laid them elsewhere, and evolution prevailed.

How Long Does It Take for Salmon to Swim Upstream?

It usually only takes salmon a few weeks to travel from the ocean all the way upstream to where they spawn. Sometimes this can be over 2 miles from the ocean! They wait until the first big rain in late September or October, then swim upstream when the rivers are high. 

Waiting for the first big rains is critical because it gives the salmon the room they need in the rivers to swim past obstacles like logs and other natural dams. If there are man-made dams in the river, oftentimes you’ll see salmon “ladders” or throughways that allow the salmon to get over them.

While you can catch most species of salmon in the ocean, the easiest time of year to catch them is when they congregate in bays and in rivers. The high concentration of large fish tempts fishermen every year to try their hand at trolling for salmon as well as bead fishing for salmon.

Why Do Salmon Die After Mating?

Most species of salmon die after mating and making the migration upriver. Why is this? Most experts believe it is because the trip takes every ounce of energy the salmon have to make it. Once they’ve swum all the way upriver and mated, there isn’t much left of their bodies anyways.

Every year some salmon do survive to come back to the ocean, however. Most experts approximate 5 to 10% of salmon successfully migrate back to the ocean after spawning.

Types of Salmon

There are 5 main types of salmon that swim upstream to spawn. The two most common species of salmon targeted by sports fishermen are king salmon and coho salmon.

King Salmon

King salmon can be identified by their large size, silvery sides, and dark greenbacks. They also have small black spots on their tails and the upper half of their bodies. King salmon usually grow larger than the other species (up to an average of 20 to 25 lbs).

Coho Salmon

Coho salmon are the other most common species of salmon and look almost identical to king salmon. Coho salmon often only grow to 10 or 15 lbs. The easiest way to tell the difference between the two is to look inside their mouths for differences. King salmon will have black gums and a black lower jaw, while coho salmon have white gums and a white lower jaw.

Sockeye Salmon

Sockeye salmon are also smaller than king salmon, growing to an average of 10 lbs as adults. Sockeye salmon are the third most prevalent salmon species behind pink salmon and chum salmon. They live in similar environments as the other species and also migrate upriver to spawn.

Pink Salmon

Pink salmon are another common species of salmon that swims upstream, and only grow to be 5 lbs in weight. Each year huge schools swim upriver in the pacific northwest every other year to spawn. Pink salmon are also called humpback salmon due to the physical changes the males go through when spawning. They grow large humps on their backs and turn bright pink before dying. No pink salmon survive after they swim upstream.

Chum Salmon

Chum salmon are probably the least targeted species by sports fishermen, but they also migrate upriver to spawn. They grow larger than pink and sockeye salmon, with their average adult weight clocking in at around 12 to 15 lbs. Chum salmon aren’t the most desirable salmon to fish for because their meat becomes bad tasting by the time they enter rivers to spawn.

How to Catch Salmon

Now that you know why salmon congregate in mass numbers each fall, you probably want to know how you can catch them. Well, you’re in luck! There are many different ways to catch salmon. We’ll go into detail on some of our favorite ways below.

Trolling for Salmon

We’ve written several articles on how to troll for salmon with downriggers as well as without downriggers. Here’s the quick summary. If you want to learn more check out the articles we linked above.

Troll for salmon in the inlets and bays that the salmon spawning rivers dump into. These areas are usually great for salmon from late August to early November depending on when it starts to rain frequently.

Use a hoochie squid or a cut plug herring and drop your bait down to 20 feet. You can do this with weights or a downrigger if you have one. Troll at 2 to 3 miles per hour, or slightly faster for coho salmon. Once you start getting bites a certain depth, switch them all to that depth.

Once the salmon run season gets going (usually in late September through October), we like to switch to back trolling in rivers with a jet boat. When back trolling, you can skip the downrigger for weights or a diver. We like to back troll with either a Kwikfish or salmon roe. Check out our detailed article on how to fish with salmon roe as bait as well as why salmon eat salmon eggs for more info.

Casting

When salmon are in high numbers in rivers, you can also cast for them with beads or bright colored spinners. Since the salmon aren’t actively feeding during this time, the goal is to annoy them into biting by casting a bright colored lure close to them. They are very territorial during this time period and will lash out at annoying lures. 

Fishing Equipment Needed for Salmon

If you don’t already have salmon fishing equipment, you should consider getting a rod and reel that are designed for catching salmon. Salmon are powerful fish and will easily overpower a small spinning rod and reel. Since nets aren’t allowed, catching salmon can be difficult and expensive.

Depending on the type of salmon you’re trolling for, different salmon fishing tackle setups are most effective. For both king and coho salmon, we recommend a medium to heavy saltwater spinning reel with 30 lb test braided line. Check out our guide on the best saltwater spinning reels for more info. 

If you’re trolling for salmon, get a traditional trolling reel or bottom fishing reel that can hold a lot of braided line.

As far as an appropriate rod, we recommend a medium strength saltwater rod that’s at least 7 to 8 feet long. Using a long rod (8 ft and over) give you more leverage to fight a strong salmon while trolling. It also adds to the flexibility of the rod so when a salmon bites your lure while trolling it gets hooked effectively. Surf rods can work if you’re in a pinch, but we recommend getting a rod specifically designed for salmon.

Salmon rods need to be more flexible than other rods, especially at the tip. This allows the salmon to take the lure and get hooked without having the lure ripped out of their mouth by the boat. The softer tip also allows you to get more flex in the rod when casting, and effectively cast the lure farther distances.

Parting Thoughts

Salmon are one of the most popular fish to fish for in the Pacific Northwest. Their fighting spirit and unique migration make them some of the most fun fish to catch. Now that you know why salmon swim upstream and have some ideas on how to catch them, we hope this season you’ll give it a go. Have your own salmon fishing stories you would like to share with us? Shoot us a note in the comments below.

Happy Hunting!

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0 thoughts on “Why Do Salmon Swim Upstream? Nature’s Great Mystery”

  1. ronald kallungi

    Yea, how did the salmon originallly “learn” to swim upstream. What would cause one to do so in the first place? Logic tells you that a fish, which is amongst the stupidest species on earth, would NEVER swim upstream on its own volition. Did the salmon stop and think, wow, there are some really great spots up there to lay my eggs.

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