Alaskan Salmon Life Cycle

When most people think of Alaskan salmon, they think of the delicious, pink-fleshed fish that can be grilled, smoked, or poached. But what many don't know is that there's more to Alaskan salmon than meets the eye. In fact, these fish have an amazing life cycle that begins in the chilly waters of the North Pacific and ends with a sumptuous feast on our dinner tables. Want to learn more about the salmon life cycle? Keep reading!

Why Alaskan Salmon are Truly Something Special 

Alaskan salmon are nothing short of legendary—and this is even before they end up as dinner! The reason they taste so delicious has to do with their migratory path from Alaskan rivers and streams, to the wild, high seas of the Pacific Ocean, and then back to where they were born. The scientific word for this is anadromous and refers to fish that migrate up river from the oceans they spend most of their lives in to spawn. 

What makes this possible is Alaskan salmon’s high levels of stored fat. Combined with Alaska’s frigid cold temperatures, the long journey to and fro requires salmon to store a lot of olis in their muscles. Fortunately for us, this translates into one of the richest sources of omega-3 fatty acids—and all of the health benefits that come with it. 

Now that we’ve got you hooked (pun intended), let’s take a deeper look at the lifecycle that includes one of the longest migrations in the animal kingdom. 

The Beginning: Small Eggs in Stream Beds

In the fall, salmon will lay their pea-sized eggs in gravel beds beneath lakes and streams. The female salmon will use her tail to dig a little ditch in the gravel, ensuring that cold, oxygenated water will reach the eggs. Several feet beneath the surface of the water, the eggs will also be protected from exposure to direct sunlight. This is crucial for the soon-to-be salmon, as their eggs are slightly translucent—so much so that you can see the developing organs through the egg shells! 

While the female is busy preparing the salmon nest, what’s also referred to as a redd, the males will stay close by to ward off any other incoming salmon. He will continue maintaining their breeding spot until the female has successfully expelled all of her eggs. At this point, the male (or multiple) will fertilize the eggs. 

After this is completed, the female will move on and repeat the process. In some cases, a single female will lay eggs in several redds, all of which will be fertilized by different males! Remember, a female salmon may lay between 2,000 and 5,000 eggs in her lifetime! Roughly 500-1,000 are laid in each redd. 

Warmer Water and Alevins

The safely buried eggs will develop slowly. As temperatures start to warm in late-winter or early-spring, the salmon—called alevins at this stage—will break through the thin shell of the egg. But they aren’t ready to head into the wild seas of the Pacific just yet. With a yolk sac still attached to their abdomen, they rely on this for food and the surrounding gravel beds for protection. 

Then The Fry Head Into Free-Flowing Water

After about 12 weeks, the salmon will consume all of the food in their yolk sac. At this stage, they’re considered fry, or young fish. With a new need to find food, fry will leave the gravel bed and head into the free-flowing waters of the river or stream they were born in. 

It’s at this stage that different species will behave slightly differently. Chinook fry prefer the slower moving water along vegetated banks. Young Coho salmon, on the other hand, like the still water found wetlands, lakes, and even beaver dams. Juvenile Sockeye salmon may stay close to calm pools, or may head directly for the sea, like Chum and Pink fry do. 

These different rearing habitats ensure that several species can live peacefully in a given waterway. Also referred to as habitat partitioning, their behaviors, even as young fish, gives them a better chance of finding food and cover—making them some of the most resilient fish we know. 

The Middle: Smolts Find the Sea

While the timeline varies between species, fry will spend one to five years living in the parr stage. During this stage in their life cycle, the salmon are still acclimating to their home rivers and streams. They’ll also develop vertical markings on their bodies. 

Then the young salmon become smolts. Smolt is the name given to the young fish who begin to move from freshwater to saltwater. At this stage, the salmon will leave the comforts of the slow-moving waters by swimming up into the current. This will help to propel them downstream to the saltwater estuaries found at the mouth of their home river. 

In fact, in these estuaries—where saltwater and freshwater mix—a significant transformation occurs that allows the smolts to experience their new salty environments. Externally, their appearance takes on a silvery hue and they’ll lose the stripes they developed as parr. Internally, they develop salt-regulating mechanisms that allow them to thrive in their new ocean home. 

Young Salmon Living in the Ocean 

When they’re ready for the new elements the ocean brings, food needs will drive the young adult salmon out into the sea. The insects, invertebrates, and small fish found in the freshwater environments are no longer enough to sustain the growing salmon. So, they’ll join other salmon to access the bounty provided by the North Pacific Ocean’s cold waters. 

Feeding on a variety of prey, the young adult salmon will grow rapidly. While their time in the ocean will vary depending on species, salmon will spend six months to six years swimming in the Gulf of Alaska and Bering Sea. 

The End (and Beginning): Return to the Streams 

Once the adult salmon reach full maturation, they’ll return to the streams where they hatched. But without GPS or maps, just how do salmon accomplish this tremendous feat? Scientists have discovered that salmon have a very well-tuned sense of smell that helps to guide them back to where they were born. How they make the entire 2,000-mile round trip, however, is still a mystery. 

Once they reach their birthplace and spawning grounds, most Pacific salmon die. But this isn’t to say that they still don't serve a purpose. In fact, the health of the waterways in which they spawn relies heavily upon salmon carcasses. The deceased salmon become an important food source for caddisfly larvae, which in turn meet around 50% of food needs for young salmon! 

Similarly, any salmon carcasses that become washed up on the shore become a food source for fly larvae. During heavy rain, the maggots wash into the water, providing yet another valuable food source for young salmon. In some cases, growing salmon themselves will also feed directly on the salmon carcasses. 

As a beautiful representation of the interconnectedness of all life, salmon carcasses are also rich in nutrients that help to restore Alaska’s thin topsoil. Due to its geologic history, much of Alaska’s coastline is depleted in nutrients that wildlife, fish, and plants depend upon. As such, salmon directly contributes to the survival of many creatures—from small birds and insects, to bears, wolves, and eagles. 

Alaskan Salmon: A True Gift to the World

Alaskan salmon are majestic creatures. Their life cycle provides a gift to humans, other fish, soil, and the local ecosystem as a whole. Not only do they travel thousands of miles to feed and spawn, but their death also provides ecosystem benefits for a range of plant and animal species. These creatures should be celebrated, which is why at Alaska Salmon Co., we sustainably harvest them to ensure that they can continue to lead such impressive lives for years to come.