Salmon have a remarkable life cycle that involves living in both freshwater and saltwater environments. This unique migration between habitats has led many to ask: Is salmon a saltwater or freshwater fish? The answer is complex, as salmon display different characteristics during their complex lifecycle.
Anadromous Salmon – Migrating Between Fresh and Saltwater
Atlantic salmon are anadromous fish, which means they live in both fresh and saltwater. Their life history begins with spawning and juvenile rearing in rivers; then migrating to saltwater to feed, grow, and mature before returning to freshwater to spawn.
During the early stages, salmon eggs incubate in gravel beds in freshwater streams and rivers. After hatching, the juveniles will continue to live in these freshwater habitats from a few weeks to several years, depending on the species.
Eventually instinct will drive the juveniles downstream in a process called smoltification. Dramatic physiological changes prepare their bodies for life in the ocean.
Once they reach the ocean, salmon will spend between one to five years feeding and growing into sexually mature adults. The saltwater environment provides an abundance of prey allowing salmon to become strong fast swimmers. Some species like Chinook salmon can reach over 100 pounds!
Finally, when it is time to spawn, salmon will use specialized sensory adaptations to navigate back to their natal freshwater streams, embarking on epic migrations of up to 3,000 miles They return to the exact location they were born to reproduce and die, completing the cycle
Classifying Salmon by Life Stage
Given their complex life history in both habitats, classifying salmon strictly as freshwater or saltwater fish is problematic. The best solution is identifying them based on their current life stage:
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Salmon eggs and juveniles in rivers are freshwater salmon. They cannot survive in saltwater until they undergo the transformation into smolts.
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After migrating to the ocean, they become saltwater salmon, feeding and growing into adults. Their bodies are now adapted to survive and thrive in the marine environment.
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Upon returning to freshwater to spawn, these saltwater salmon undergo changes to become freshwater salmon once more.
So salmon display a range of adaptations to different saline environments during their migration between realms.
Landlocked Salmon – Surviving Entirely in Freshwater
While most salmon follow the anadromous life cycle, some populations have adapted to live entirely in freshwater. Landlocked salmon are born, grow, and spawn in lakes and rivers with no access to the ocean.
Landlocking can occur due to:
- Natural barriers like waterfalls blocking migration routes
- Dams constructed by humans preventing ocean access
- Introduction of salmon to landlocked habitats by humans
Despite spending their whole lives in freshwater, landlocked salmon exhibit strong instincts to migrate downstream to the ocean. If given access, they would likely thrive there. But circumstances force them to complete their life cycle restricted to lakes and rivers.
Remarkable Physiological Adaptations
The ability to thrive in freshwater and saltwater requires remarkable physiological adaptations in salmon.
When moving into saltwater, salmon undergo changes in osmoregulation. This process controls water and ion balance in their bodies. Salmon alter their gills and kidneys to actively excrete excess salt while retaining water.
Hormonal changes also assist with managing the stresses of transitioning between dramatically different saline environments. Cortisol and growth hormone help regulate osmoregulation and promote growth in the ocean.
In essence, salmon have evolved finely-tuned mechanisms that allow their bodies to shift between freshwater and marine realms. This underlies their success in exploiting diverse habitats across their extensive range.
While they are genetically programmed to use both realms, at distinct life stages salmon can be characterized as either freshwater or saltwater fish depending on their specific habitat and transformations. This marvel of nature highlights the remarkable resilience of salmon in overcoming the osmotic challenges faced in their epic journeys.
How Do We Know About Osmoregulation?
In 1957, a Danish chemist named Jens C. Skou discovered that animal cells that control nerve impulses, muscle contractions, and digestion require more potassium inside the cell than outside it. Likewise, the cell needs more sodium ions outside the cell than inside it. Skou discovered an enzyme in our cells called Nz+/K+_ATPase — or NKA for short — which acts as a pump to transport these sodium ions in and out of cell walls. Many cells spend a fifth of its energy on these pumps; nerve cells spend 2/3rds of their energy moving around sodium ions. For his research, Skou won the Nobel Prize in Chemistry in 1997.
Salmon use NKA pumps to move sodium in the right direction. In freshwater, salmon pump sodium in, but once they enter the ocean, they begin pumping out sodium and chloride ions extracted from ocean salt that enters their bodies.
Can People and Animals Drink Seawater?
Marine animals, like sea otters, have efficient kidneys that help flush out salt from the seawater they live in. U.S. Fish and Wildlife Service
If salmon can survive in saltwater, why can’t human beings and other animals do it too? Most animals are only adapted to live either in freshwater or saltwater. Humans can’t produce urine that’s saltier than blood, and ocean water has three times more salt than our blood. Our kidneys can’t filter out the salt in seawater, and we become dehydrated over time.
Some marine animals, known as osmoconformers, don’t drink water the same way we do. Instead, invertebrates like shrimp and jellyfish take water in through their skin, filtering out the salt as they do. Like salmon, saltwater fish have efficient kidneys that can remove excess salt through urine, gills, and skin. Seabirds have efficient kidneys, as well as special glands to manage saltwater. The birds can dribble salty water out of their beaks. The kidneys of marine mammals, such as sea lions and whales, are also especially adapted for flushing out seawater. The urine of those animals can be up to 2.5 times more salty than seawater.
The Salmon’s Life Mission | Destination WILD
FAQ
FAQ
Is salmon a freshwater or saltwater fish?
Salmons are special fishes. Generally, fishes either live in freshwater or the ocean, but salmons often live some part of their lives in both. They are anadromous fishes, meaning they spend part of their life living in freshwater streams and part of their life in the salty ocean.
Are salmon farmed in fresh or saltwater?
Salmon farming involves raising salmon throughout its lifecycle, which takes around three years. The first year of production takes place in controlled freshwater environments, and then the farmed salmon are transported to seawater where they stay through to harvest.
Are salmon caught in freshwater?
Some salmon are caught in ocean fisheries, some are caught in inland marine and freshwater fisheries, and some salmon complete their journey back to their …Oct 6, 2022
Is salmon a salty fish?
Salmon itself is not inherently salty. While wild-caught salmon from the ocean may have a slightly salty or briny taste, it’s not a heavily salty fish like some shellfish or processed fish. The sodium content of fresh salmon is relatively low, typically around 40-80 mg per serving.
Are salmon saltwater or freshwater?
Salmon are both fresh and saltwater fish. They spend their early life in freshwater, migrate to the ocean, and then return to freshwater to spawn. This unique life cycle is a key characteristic of salmon and sets them apart from other fish species. Key Points: • Salmon are anadromous fish, meaning they migrate from the ocean to freshwater to spawn.
What is a freshwater fish called?
Sometimes the terminology used for the freshwater forms of saltwater fish is confusing. Atlantic salmon that exist in freshwater lakes without access to the sea are popularly called landlocked salmon or landlocked Atlantic salmon to distinguish them from the saltwater version. Some folks may refer to them simply as freshwater salmon.
Is salmon a cold water fish?
Salmon (Salmo salar) is a species of fish that belongs to the family Salmonidae. It is a cold-water fish that is native to the northern hemisphere, primarily found in the Pacific and Atlantic Oceans. Life Cycle of Salmon Salmon are anadromous fish, which means they migrate from the ocean to freshwater to spawn.
What is a salmon fish?
Before we dive into the debate, let’s define what salmon is. Salmon (Salmo salar) is a species of fish that belongs to the family Salmonidae. It is a cold-water fish that is native to the northern hemisphere, primarily found in the Pacific and Atlantic Oceans. Life Cycle of Salmon
How do saltwater salmon become freshwater salmon?
After smolting and migrating to the ocean, they become saltwater salmon, feeding and growing to adulthood. Their bodies are now adapted to marine life. Upon returning to freshwater to spawn, saltwater salmon undergo physical changes to become freshwater salmon once again. Under natural conditions, virtually all salmon migrate to the ocean.
Are fish specialized for freshwater or saltwater?
Most fish are specialized for either fresh or saltwater. If freshwater fish enter saltwater, water will rush into their bodies, stretching cells until they burst. The opposite happens to saltwater fish in freshwater. Salmon, however, have adaptations that enable them to transition between fresh and saltwater: