Salmon are known for their spectacular migratory journey, traveling thousands of kilometers from the vast ocean back to the freshwater regions where they were born to spawn each year. However, this journey is fraught with countless difficulties, challenges, and even a high risk of mortality, making it one of the most dangerous adventures in the natural world.
Salmon primarily inhabit the oceans of the Northern Hemisphere, with their body length typically around 60 cm. However, what makes this species particularly remarkable is their migration journey back to their birthplace for spawning.
The spawning season for salmon usually occurs in the spring. Female salmon lay their eggs upstream, while male salmon quickly swim upstream to provide sperm for the female’s eggs. It is during the spawning season that female salmon encounter males. After fertilization, both male and female salmon will swim back to the sea, and the hatchlings will live near river mouths.
Salmon are typically born in freshwater rivers and streams and then migrate to the sea. This process requires salmon to adapt to significant changes in temperature, salinity, and flow. When moving from freshwater to saltwater, their bodies must adjust to maintain homeostasis, which is a major physiological challenge.
The salmon’s journey begins in the ocean, where they have lived and grown for many years. Upon reaching maturity, salmon recognize the call of their homeland and begin the upstream journey back to their birthplace.
The migratory path of salmon often consists of long, swift rivers with many waterfalls and rocky rapids, where they encounter predators such as coyotes and brown bears, and must overcome various obstacles along the way. To navigate these challenges, salmon require strength, resilience, and extraordinary swimming abilities.
During their migration, salmon become favored prey for many wildlife species, including bears, sharks, hawks, and larger salmon. They must remain vigilant and rely on their survival instincts to evade aggressive predators.
During their migratory journey, salmon face many predators such as bears, hawks, and larger fish. Throughout the journey from river to sea and back again, salmon must always be on guard and avoid attacks from these predators. Especially during spawning periods when they gather in large numbers in shallow waters, the risk of being attacked is even higher.
To cope with fierce predation, salmon have developed various survival strategies. One important strategy is mass migration. When millions of salmon migrate simultaneously, the survival chances of each individual increase due to the large numbers, reducing the likelihood of any single salmon being captured. This phenomenon is known as “the herd strategy.”
Salmon have also evolved to adapt to their surroundings. Their ability to change color to camouflage with the surrounding water helps them avoid the attention of predators. Additionally, salmon possess the ability to swim quickly and powerfully, enabling them to escape threats swiftly.
This continuous process of selection and elimination has endowed salmon with unique skills. Some salmon have even learned to cross roads to overcome obstacles and evade natural predators.
After climbing over waterfalls or rocky rapids, they face another dangerous area, where a large number of brown bears congregate. Shortly after waking from hibernation, these brown bears head to the riverbanks to search for food. At this time, the bears simply wait at the top of the waterfall, mouths open, waiting for salmon to jump up.
In some areas of North America, when it rains heavily, low-lying areas along the migration route will be flooded. During this time, a large number of salmon will gather in the shallow creek and jump onto the road, crossing the flooded area and entering the river on the other side. In fact, the accumulated water serves only to lubricate the path. Salmon rely on their tail flicks to propel their bodies forward. By crossing these roads, salmon can shorten their migratory distance and reach spawning grounds faster.
Salmon are born in freshwater rivers, where they spend their early life stages before migrating to the open sea. This journey begins when young salmon (known as smolt) move from the river to the sea in search of abundant food and to grow into mature salmon. After spending a few years at sea, salmon will return to the very river where they were born to spawn and complete their reproductive cycle. This process requires them to traverse thousands of kilometers, overcoming waterfalls, strong currents, and many fierce predators.
Human activities also complicate the migration journey of salmon.
In fact, in recent years, human activities have further complicated the migratory journey of salmon. Humans build dams and hydroelectric projects that obstruct the natural migratory routes of salmon, reducing the number of salmon that can return to the rivers to spawn. Pollution of water bodies also degrades the habitat quality for salmon, making them more vulnerable to predators and diseases.
Climate change is also significantly impacting salmon habitats, making their migratory journey even more arduous. Warming ocean temperatures, droughts, floods, and other extreme weather phenomena are becoming increasingly common, affecting food sources, spawning grounds, and the ability of salmon to migrate.
To protect salmon and ensure their survival, several measures have been implemented. Constructing fish ladders and special water routes helps salmon navigate past dams and artificial structures. Additionally, nature reserves and artificial salmon breeding programs have been established to maintain and restore wild salmon populations.
Climate change is also significantly impacting salmon habitats.
The migratory journey of salmon is one of the most remarkable feats in the animal kingdom. However, this journey is also fraught with dangers, from natural predators to challenges posed by humans. The survival and development of salmon require relentless efforts from themselves, as well as support from humans. Protecting and preserving salmon habitats not only ensures the survival of an important fish species but also contributes to the ecological balance of freshwater and marine ecosystems.
