|Did You Know…?
Against All Odds
Around the world, the changing seasons and an indefatigable determination to survive impels many creatures of air, land and water to make an all out do-and-die journey home to the place where they were born. It seems to be part of the Creator’s design for a myriad species of fish, animals, birds and even insects. To observe the remarkable ability of these creatures to navigate, some thousands of miles against incredible odds, is to think about the great Designer who really is able.
Among such creatures the salmon is champion.
As with most creatures, there are various species of salmon. Most popular is, perhaps, the king salmon. An Atlantic species, this salmon has tipped the scale to as much as 126 pounds. But this is small compared to the fossil record of one which claims a weight of about 500 pounds, a length of ten feet, and is even equipped with fangs for battle. (How would you like a creature like this to swim up beside your boat?)
A salmon’s life is one of change. Progressing from an egg, to an “eyed egg,” to an alevin, to a fry, and finally to a parr, the salmon is finally ready to begin its incredible preparation for life in the ocean. Adapted for life in fresh water, it would quickly die in the ocean. But the ocean is its destination. Depending on the species, it begins migration to the ocean about a year after hatching (chum and pink salmon begin their migration to the ocean no more than a week or so after hatching!).
How will it survive when it gets to the ocean? Well, it won’t—not without the masterful handiwork of the Creator.
Before reaching the estuary (where fresh and salt water mix), the fingerling undergoes a dramatic change called smolting. The fish become more streamlined, their tails become more elongated and forked, the parr marks (vertical bands on their sides) disappear and turn to a very silvery color. Simultaneously, internal changes take place. The memory and smell centers in the brain grow rapidly. (These are special features, as amazing as it may seem, that the Creator built into the salmon for a special purpose which you will later see.) Also, the salmon’s kidneys convert to be able to excrete salt instead of retain it!
After reaching the estuary, the young salmon remain for a short time while the final stages of smolting are completed.
Before it was a fresh-water fish which would quickly die in the ocean. Now it is fully adapted for vigorous and competitive life in the deep salt water. But its traveling days are far from over.
Budding strength shines through a ten-week-old salmon as it breaks free of its embryonic membrane. For several more weeks it lives off its yolk sac, then rises to eat microscopic plants and larvae. Turning silver two to four years later, it heads downstream, developing a tolerance for salt water as it enters the sea.
Traveling in schools the Pacific salmon migrate to the North Pacific Ocean where they remain for one to seven years, depending on the species. For some, it is a long journey of 3,000 to 3,500 miles—actually much further, because salmon do not swim in a straight line. The Atlantic salmon travel to Nova Scotia, Newfoundland, Labrador, and even to East and West Greenland.
Salmon swim in the ocean an average of 18 miles per day and can maintain a speed of 34 miles per day for long periods.
Salmon have a row of sensory pores called lateral lines along their sides which help them navigate. The sensory pores provide a means of hearing low frequencies which help to detect very small ocean currents. They also help to find food and avoid predators. Some Sockeye salmon also use the sun and moon for navigation.
The Atlantic salmon spend different lengths of time in the ocean before returning to their home-rivers for spawning. Some spend one winter, others two, others three winters in the ocean. Could the Master Designer have built in this feature so all the eggs would not end up in one basket?
Incredible Journey Home
An instinct for procreation so strong that it could only be by the Creator’s design, the salmon changes course and heads home.
How can they find their way to the place where they themselves were given life? Remember the rapid growth of memory and smell centers of the brain? Now they put these features to good use. Salmon have a sense of smell hundreds of times more acute than that of a dog. Scientific studies show that they can detect one part per million, which is the equivalent of one drop of their home waters in 250 gallons of water. The Creator not only gave them this ability but also the ability to recognize their home-waters by smell.
After traveling thousands of miles they finally pick up the scent of their birthplace, whether a hatchery or a stream, and they change direction once more. Then come the long, seemingly impossible odds of navigating the rivers upstream. Some of the chum and king salmon of the Pacific swim more than 2,000 miles up the Yukon River and its headwaters. Impelled by a built-in desire to navigate to the site where they were hatched, they fight rapids, and can leap falls more than 12 feet high! When they come to a fork in the river, they know just which one to take—they remember!
The Sockeye salmons’ arduous years-long journey leads from river to ocean and back to river again. Young salmon (called parr) spend their first four years in the fresh waters of the Alaska rivers, before embarking on their “swimathon.” Along the way they undergo a major physical change (smolting) to be able to tolerate the salt waters of the Bering Strait. Continuing their migration, they change again as they return to the fresh waters of their home rivers after years at sea, where they fight the current upstream to their ancestral spawning grounds. Reaching “home port” they muster the energy to spawn— and die.
The life cycle of the salmon is delicate. The odds against survival from egg to the return to the spawning grounds are very high. Only two to ten percent live to make the journey.
From the time the eggs are deposited beneath the gravel of a stream they must be provided with cold, clean, swift water. Without the swift-movement of clean water the incubating eggs will suffocate due to lack of oxygen. If the water becomes too warm the salmon will become infested with disease. As the climate becomes warmer, and due to deforestation, warming water has become a concern. Many die from this cause alone, and the threat grows every year.
Another threat to salmon is that of predators. Fish and small animals are always ready to snatch a young salmon during migration. Studies indicate that about 97% of Maine salmon migrate at night to avoid predators as they swim backwards downstream seeking the safety of deep areas. The Pacific king and coho salmon are prized sports fish, and the Maine salmon, now listed on the endangered species list, is also a favorite sports fish for fishermen. While in the ocean they are fair game for a variety of predators including seals, porpoises, birds-of-prey, and other large fish. They swim in schools in the ocean for protection, displaying their flashy silver sides to confuse predators. Migrating back up the rivers many are met with hungry bears anxiously awaiting their return.
Before beginning this long and difficult journey, the salmon must be prepared. Why? While making this amazing journey of two months or more and thousands of miles, it is said that they never eat a bite of food! Their one purpose is to reach home and spawn.
One Last Change
When in the salty waters of the ocean they are a bright silver. But when making their way up the rivers other changes takes place, varying according to the species and the inland distance traveled.
The male Pacific salmon generally develop hooked jaws, and their gills turn a bright red as they begin their inland journey in fresh water. By the time they reach the spawning grounds, some of the salmon are bright red, others green, brown, striped, and even purple. These colors are most pronounced in males. One species grows large canine teeth from which it gets its name, dog salmon.
The Pacific salmon’s life ends with the process called spawning. While the Pacific salmon spawns only once and then dies, the Atlantic salmon may live to spawn three or more times before dying.
Once salmon reach the spawning grounds, the females choose a site and prepare nests (redds) for laying eggs. They lie on one side and rapidly move their tails back and forth over the gravel. Hardly touching the gravel with their tails they create water currents that wash away the gravel. (Some of the gravel can be as large as a fist!) These redds are about 6 inches deep. This process takes up to a whole day. They then deposit from 500 to 1,200 eggs while the males fertilize them. After covering the eggs, they move upstream, where the process is repeated for as many as four more times, until a total of 2,500 to 6,000 eggs have been deposited per salmon, depending on the species. Why so many eggs? The Creator has made this provision for the benefit of many creatures, not the least of which is man. By the time the females have finished spawning, they have lost half their weight.
Through dogged determination, strength and navigational abilities that only an intelligent Creator could provide, they have accomplished their mission. With what strength is left, the adult Pacific salmon guard the site until their death as an instinctive loyal duty dictates. Interestingly, the decaying bodies of these fish form a plentiful food supply for small organisms which are the main food source for the hatching offspring.