Salmon make a huge journey every year: they swim upstream from the ocean to spawn in the rivers and streams where they were born. This journey is integral to the salmon life cycle. What makes these fish strong enough to swim against river currents for hundreds or even thousands of miles to get where they need to go? The answer is very interesting.
As an avid angler and salmon enthusiast, I’ve long been in awe of the salmon’s ability to migrate upstream against the flow After researching the science behind their swim, I’ve gained an even deeper appreciation for this iconic fish. Let’s dive in and explore what enables salmon to achieve their incredible freshwater migration year after year
Powerful Muscles and Efficient Physiology
Salmon have muscular, streamlined bodies perfectly adapted for long distance swimming. Their fusiform shape and smooth scales reduce drag as they cut through the water. Salmon also have a complicated musculature that provides the consistent power needed to swim against strong currents for extended periods.
Their metabolism is incredibly efficient, allowing salmon to convert food energy into sustained muscular exertion. Salmon get most of their energy from fat stored in their flesh during ocean feeding. This gives them a dense, oil-rich meat. Salmon metabolism uses oxygen at an amazing rate to burn this fat and energize their muscles.
Salmon cardiac physiology is also designed for non-stop swimming. These fish have huge hearts relative to their body size allowing them to constantly circulate oxygen-rich blood to their muscles. This gives salmon seemingly unlimited cardio endurance.
Instinctual Drive and Navigation
While physical adaptations allow salmon to make their journey, internal drives and navigation keep them oriented in the right direction. Salmon have an irresistible instinctive urge to return to their natal waterways to spawn. This homing behavior is imprinted from birth.
Salmon remember smells and can pick up on the unique smell of their home river even when they are far away at sea. They also use the earth’s magnetic fields to help them find the right way to migrate. It’s this unwavering instinct that keeps salmon swimming upstream at all costs.
Highly Hydrodynamic Body Design
The salmon’s exterior design assists their non-stop swim as well. Their streamlined shape and smooth skin minimize drag and turbulence – think of how sleek a bullet travels through the air.
Special grooves along their flanks, called sinusoidal body waves, further reduce drag as they undulate through the water. Salmon also have broad, powerful tails that deliver maximum forward thrust with each stroke.
Ability to Clear Obstacles
Rivers present many obstacles like waterfalls, rapids, and dams. Salmon have adapted the ability to leap several feet vertically to clear such impediments. By swimming down and building momentum, salmon can launch themselves high out of the water to pass otherwise impassable barriers.
Their fingernail-hardened scales protect the fish as they crash into rocks and logs in turbulent waters. Salmon will continue trying to jump an obstacle until they either clear it or die of exhaustion in the attempt.
What enables salmon to achieve their incredible migratory feat is a combination of physical, instinctual, and evolutionary adaptations. Powerful muscles, efficient metabolism, and a hydrodynamic form all fuel their non-stop upstream swim. Homine instinct and navigational abilities guide salmon through vast distances to their birth rivers. The salmon’s iconic life cycle persists thanks to these amazing natural adaptations.
Salmon & Steelhead Spawning and Salmonid Reproduction
S almon (derived from the latin term salmo which means leaper) have one of the most interesting life cycles of any animal on earth. Born in a fresh water stream and then migrating into the ocean to live in salt water, they migrate for thousands of mile before returning to their natal stream to spawn. This behavior is called anadromous, and salmon are not the only fish that are born in fresh water and spend the majority of their lives in salt water. Sturgeon, trout, and many other fish do the same thing. In South American Rivers, sharks are anadromous. What makes the salmon special? Let’s pursue this topic in further detail.
Some fish are catadromous (opposite of anadromous). As part of their life cycle, they are born in salt water and move up rivers to find food. A classic example of this type fish would be the American eels common to North American Rivers. A lot of the time, eels and lamprey will “hitchhike” up river on the backs of salmon and trout that are migrating.
There are many kinds of salmon in the world, but these five are only found in North America. You might see them when you go salmon fishing in Alaska. These are the king salmon, silver, sockeye, chum and pink salmon (ordered largest to smallest). All pacific salmon die after spawning. There is a chance that Atlantic salmon will live through spawning and go back to the ocean to keep growing and spawn again or again. The steelhead, also known as the rainbow trout, is a species of Pacific salmonid that can live an anadromous life in the ocean and spawn more than once. The life cycle of the steelhead is nearly identical to that of the Atlantic salmon. Cutthroat trout, brown trout, dolly varden, and many other types of trout and char can also make it through an anadromous spawning journey.
Pacific salmon are unique in that spawning is the last act of their life cycle. One amazing thing about salmon is that they can find their way back to their birth stream after migrating thousands of miles across the ocean for years. Some studies have shown that a salmon can find its way back to the stream it was born in by using its sense of smell. Other research shows that the earth’s magnetic field can affect the brain of salmon, which may play a role in their instinct to find their way home. No matter what makes salmon able to do this, the fact that they can find where they were born after migrating thousands of miles is truly amazing.
Why Do Salmon Change Shape When they Spawn?
Salmon change physically when they move from living in saltwater to living in freshwater in which they were born. This transition affects the appearance of the fish very radically. Not only do they stop feeding, but they also undergo a color and shape change. The male salmon typically forms a curved mouth (called a kype) with large canine like teeth. The males of some species form a hump on their back during their transition. The female salmon do not undergo such a radical shape change, but do undergo significant color changes.
During the upstream migration to spawn, the male of the species acts as a guardian and tries to win the favor of a suitable female. For the fisherman, this means that the male fish are more likely to attack a lure or bait that comes into their territory. We think that the reason females will also hit lures and baits is because they are protective or because they want to keep feeding.
Once a dominant male and female fish have paired up to mate, the female starts to clean a gravel bed that gets a lot of oxygen by sweeping her tail over it. The female will select an area in the streambed that has an upwelling of water through the gravel. Based on the size of the fish, a spawning redd can be anywhere from 2 to 10 feet long and 1 to 6 feet wide.
While the female prepares the spawning bed, which is called a “redd,” the male watches over the area by swimming around what the female is doing and biting anything that gets in the way, even smaller male fish. Fish often spawn in water that isn’t very deep, which makes them easy prey for birds, bears, racoons, people, and other animals.
It is important to note that fish are not good for eating at all by the time they are ready to spawn. Salmon flesh that was once red, is now be white and mushy. In every state, it is illegal to disturb spawning fish. Fresh fish that have just been taken out of salt water are the best to eat. Fish that are ready to reproduce are not.
The male and female line up next to each other for the actual spawning ritual once the first redd is done. As their bodies shake next to each other, the female spreads her eggs and the male spreads his milt. Fertilization occurs in the water as the eggs drift down into the gravel.
Once the eggs are set, the female swims upstream and swings her tail across the riverbed to cover the nest of eggs with clean gravel. After that, the female will dig another redd nearby, and the male will stay with her to watch over the area.
If the male of the pair gets eaten, another male fish may fertilize the eggs that the female will lay in the spawning beds. Usually, the bigger male fish is in charge, but sometimes, several small male fish can fertilize the eggs of a big female fish. This tendency probably allows for genetic diversity among the species.
The eggs will hatch in 30 to 90 days or more, depending on water temperature. There are types of salmon that will move to the ocean just a few weeks after hatching from gravel. Others may stay in the river’s freshwater for one to two years before moving to the ocean.
People usually think that each salmon will go back to its birth stream to spawn, but this isn’t always the case. Salmon do stray from one steam into another watershed. This could be nature’s way of making sure that the genetic makeup of these fish is diverse and that rivers that have been damaged by natural disasters will be filled with salmon that can survive in those conditions. We can only guess at the mystery of the salmon life cycle based on what we know about these amazing fish right now.
How Salmon Swim Upstream
FAQ
What enables salmon to swim in a river?
Why do salmon spawn in rivers?
How are salmon able to swim upstream?
Why do salmon swim high up rivers?
The migrating salmon need cool and well-oxygenated water simply to be able to make the entire journey upstream and once the eggs are laid (usually in gravel beds), their continued survival heavily depends on the presence of oxygen in the water. Yet another reason for the salmon to swim high up the rivers is security.
Why do salmon swim so fast?
The design of salmon enables them to swim at remarkable speeds by reducing water resistance, whether they are in calm lakes or turbulent ocean currents. Moreover, their overlapping scales create a smooth surface, enhancing their swift swimming ability and making them naturally aqua-dynamic.
Can you catch salmon if you swim upstream?
While not being in much of a feeding mood, it is possible to catch salmon while they swim upstream in rivers. Many salmon are caught on dry and streamer flies during their journey up the rivers. As the flies usually just pass them by fairly quickly, due to the fast current, I don’t believe they take them because they are hungry.
How many miles can a salmon swim in a day?
In a river free of obstacles (such as dams, sunken trees, big stones, etc) and with a lower than average flow, a salmon might manage to swim 20 or more river miles upstream in one day.