Eyewitness II; #104; Fish

This is a. Presentation of this program was made possible by the Corporation for Public Broadcasting and bi annual financial support from viewers like you. (Musical introduction) Beneath the surface of the waters of the earth, there is another world -

greater than our own and yet we hardly know it. It is the world of fish - vast, strange, and spectacular, with creatures more extraordinary and far more varied than any on land. (music) Masters of three quarters of the planet with more species than all birds, reptiles, amphibians, and mammals added together. Representing the sky by Pisces, the symbol of rebirth and regeneration. The sign that completes the circle of the zodiac. Perhaps because of the life cycle of this fish - the salmon. The king of fish, unmatched in a

agility and acuteness of senses, in memory, stamina, and intelligence. The salmon is the adventurer of the deep. For it's life is an epic journey. From its birth high up in a shallow stream, The salmon swims thousands of miles downstream to the river's mouth and into the wide ocean. Across many waters and habitats, then finally to return to the very place of its birth. And where the salmon goes, people follow. Over 8,000 years, this fish was the main source of food for native tribes living along the rivers of the north west coast of America. They built their lives around the salmon and it's journey and their descendants still call themselves the salmon people. Years ago, the earliest fish had no jaws, no fins, no scales.

But they did possess one revolutionary feature - a strong but flexible support running the length of the body. The spine - a feature so important that without it there would be no birds, no reptiles, mammals, or humans. And upon this spine, evolution moved forward. Fins grew for steering. Some fish developed the skeleton of soft cartilage which led to the shark and the ray. Most formed scales for protection, a swim bladder for buoyancy, and a skeleton of hard bone. For the last 100 million years, this design has been the prototype of almost every fish, including the most famous fish fossil of all - the coelacanth. Thought to have died out at least 80 million years ago but then in 1938, scientists were stunned to find the coelacanth living off the east coast of Africa. The only people who weren't surprised were local fisherman, who for years had used the course skin of the coelacanth as a roughening tool when

patching the inner tubes of their bicycles. For its first few months, the young salmon stays in the stream growing and gaining strength. But then when it's still only four inches long and weighing just a few ounces comes the irresistible urge to find the sea. The fish head downstream in schools or shoals, travelling up to five. Every part of the fish's body and every sense is geared to one aim - survivol - And survive it has, diversifying into nearly 30,000 species. Many have vast egg laying powers. The ocean sunfish can lay 300 million eggs at one time. And we acknowledge this abundance with encouraging words at a time when love breaks down: there's plenty more fish in the sea. And indeed there are, from the small fry to the formidable. In South

America, there are twelve hundred species of catfish alone. Some are 13 feet long, weighing twice as much as the biggest land cat. The Atlantic Ocean holds more than one trillion herring - 500 times all the human beings on the planet. If all the fish in the world were to live on land, every continent would be piled high with fish bowls. So What makes a fish? Despite their variety the most share the same basic features. A bony skeleton supported on the spine. To maintain their buoyancy - a swim bladder - a bag filled partly with air so they neither float nor sink. Fins for fine movement and steering and to breath, fish use gills which suck in water and pass it over a tightly folded surface rich with blood vessels ten times as big as the entire area of the fish's skin.

Fish also have a unique organ - the lateral line - running the length of the body on either side. A special tube filled with fluid and jelly feels tiny changes in water movement and pressure so that the fish instantly senses its surroundings. All fish possess external protection - scales - tiny transparent plates made of hard bone for strength, overlapping for flexibility. and movement. Most fish swim with an S wriggle. It begins with a tiny sideways motion of the head growing as it sweeps along the body, pushing the surrounding water sideways and backwards. So the fish has to move forward. With a shape so sleek, it's been imitated whereever aerodynamics are an essential. And when it comes to color, fish cover the spectrum. There is no known color which is not found on the body of the fish.

No other group of animals grows so much in size from hatched young to mature adult as the fish, or ranges so widely in speed from a sea horse with a weak dorsal fin that weaves it along at a mere 50 feet in an hour. To the sailfish faster than any land animal capable of speeds of over 60 miles per hour. But there is one great boundary that divides all fish into two clear and different groups. The barrier between river and sea, between fresh water and salt water. Few fish can cross that barrier but the salmon is one of them, Changing its body chemistry from a freshwater fish of the river to a salt water fish of the sea. Now about a year old and weighing less than a pound, the young salmon brave the vast ocean. In all fish, the driving force is survival - to eat and not be

eaten. For every attack, there is a defense. And for every defense, an attack. Some feel for their prey. Some actually fish for it. And some fall for it. The image of gulping down whole has led to stories of sailors like Jonah being swallowed by creatures of the deep. While people have no trick to avoid being eaten, fish have devised unique ways to avoid ending up on the predator's plate. The puffer fish can swallow water and puff itself into a huge ball on

demand, turning it from a tasty morsel into an impossible mouthful. But the most successful form of defense and attack is nature's great game of deception - camouflage. The startling Razorfish hides among the weeds. And many other open water fish are double camouflaged, taking on the tones of their surroundings from above and below. Humans have also learned the benefits of disguise. For the early Christians, this was a way to avoid persecution and death. They used codes and signs to recognize each other, and their secret symbol

was the fish. They chose the fish because in Greek, the initial letters of the phrase "Jesus Christ, Son of God the Savior" spell out fish. Now the salmon is also camouflaged for open water, and as it feeds and grows, its strength will enable it to swim far across the ocean. Others seem less gifted yet have their own tricks. The Amazon Leaf fish is perfectly disguised, playing dead among the leaves floating in the water until its prey comes within range. The bleny retreats into a hiding place. And when it sees a threat, the garden eel just isn't there. Some rely on the defenses of others to protect themselves like the cardinal fish which hides among the poisonous spines of sea urchins. In many cultures, even humans have received protection from fish. In Hinduism,

Matsea, the fish God, saved Manu, the first man, by warning him of the coming flood and advising him to build a boat loaded with the seed of all things. Then the God towed Manu and the boat to safety. The greatest danger to fish comes from their own kind. Fights over territory guarantee the species will be spread out, ensuring food for all. These fights can be dangerous, sometimes fatal. But even when strength is ill matched, it is the intruder who is most often driven off. Sometimes the survival battle is against the environment. The ice fish contains no blood but instead a transparent plasma with its own antifreeze to keep it alive in water so cold that any other fish would die in seconds. And at the other extreme, tilapia survive where no other creatures can -

in the searing heat of volcanic soda lakes. But surely the most alien fish are far beyond human eyes in the vast depths. The ocean's deepest trough goes down seven miles, almost one and a half times the height of Mount Everest, with a pressure that would crush most fish instantly. How can any creature possibly survive down here? These fish have a feather-like skeletal and a body completely devoid of air. At such depths, they spend their entire lives in eternal darkness. To compensate, many of these remote fish actually create their own light using organs with illuminous mucus, eyes, or teeth, or in the case of the lantern jaw - the tongue. Some even have illuminous flat dangling inside the mouth which they opened to draw in prey. Others have illuminous bacteria hidden under a flap of skin to be flashed occasionally. It is surely the strangeness of these creatures which has caught the imagination of man,

uncannily calling forth his most primal fears. Small wonder that for centuries, sailors return home with fish stories of a different kind. Sea monsters formidable enough to swallow a ship, frightful enough drive sailors mad and fascinating enough like the fetching mermaid to bewitch and beguile, apparitions to be treated with respect. Most of the time. But to prove truth is stranger than fiction, enter the flatfish. At two

weeks old, Flounders place and all flatfish look like normal fish. But something is happening to the head. The right eye moves towards the center and then over the front of the skull to the other side. At the same time, the fish begins to swim on its side. A week later, both eyes are on the top of the head and only its mouth shows it once swam upright. In the next few days, the upper side of its body will take on the colors of the sea floor, and after seven weeks, it is a perfectly camouflaged flatfish. Out in the ocean, the salmon has also changed, two years old and growing fast. Its body is a mass of muscle. It now feeds on crustaceans and small fish. Indeed, the diet of shrimp has turned the flesh of the shoal into the familiar salmon pink so prized by chefs and gourmets. And other hungry predators. (water gurgling and music)

The shoal, like the beehive on land, the supreme underwater community. It leads the individuals to food-rich waters, and some find mates within the shoal. The shoal offers a valuable line of defense - safety in numbers. A predator needs to select a single target - almost impossible. And a dense shoal moving in unison can appear as a single, much larger creature. Each fish using its lateral lines to feel the movement of the shoal and respond instantly, the ultimate synchronized swimmers. So how do fish work in such close harmony? How good are fish senses?

Many fish have amazing eyesight, spotting the distinctive markings of their own kind. Fish have their own form of hearing. A fish's inner ear feels pressure waves from water movement in the same way that our ears sense what is going on in three dimensions around us, and it is this which enables the fish to orient itself. Some fish also have senses we don't possess. Some eels navigate by use of electricity, using the six thousand electric cells on their body to send out small shock waves and feel their surroundings, or with a power surge of 500 volts. They kill their prey outright. But fish do have one talent in common with us. They can talk, often at high frequency and inaudible to us, but the fish's world is alive with sound. The Garibaldi fish clicks like a metronome to attract a mate. (clicking)

And when confronted by unwelcome advances, the female cichlid knows how to say no. While the brooding Sergeant-Major fish squeaks like a mouse to ward off intruders. Fish make sounds all the time to mate, navigate, threaten, and cooperate. Indeed, fish often form partnerships where the gain is mutual. The sea anemone is home to families of clownfish who produce a special mucus to protect themselves against the poisonous tentacles while they feed on the remains of the anemone's victims. And the eight foot grouper is host to tiny cleaner RAS, even in its mouth. The grouper gets a dental cleaning and the RAS gets a free meal. On the reef, other fish gather at cleaning station to be attended by the RAS. It even advertises its service with a kind of calling card dance.

But one of the strangest partnerships of all is that of the Gobi and the shrimp. The alpheid shrimp is a prodigious digger of tunnels but has very poor eyesight and cannot see danger or find its way home when it goes in search of food. The Gobi also likes to live in tunnels. It can't dig them but it does have very keen eyesight, so the two of them set up home together. The Gobi stands guard at the tunnel entrance, alert for any danger, while the shrimp collects food and keeps the tunnel clear. Enterprise and perfect cooperation. After two to six years traveling the seas, the salmon now feels the urge to return home to the stream where it was born. It crosses hundreds of miles of ocean using only its honing instinct and a powerful sense of smell to

find that one particular river. Reaching the river, the salmon's body has to readapt to the fresh water. It waits quietly now for this last transformation to be complete. Some fish are already finding mates and pairing off. And so, the final leg of the journey begins. In other waters, countless different mating rituals are taking place, exhibitions of color and display. Most fish reproduce by laying eggs fertilized outside the body in the water. For many species, these fertilized eggs are simply left to the mercy of the currents and hungry predators. Some make nests for their eggs, fiercely guarding their young as they grow and develop. And some fish go to extremes to protect their babies. This mouth Bruder

isn't eating their young but sheltering them in her mouth as danger threatens. Occasionally, the roles of the parents are reversed. For the seahorse, it's the male which rears its young, fertilizing and storing the eggs in a pouch in the front of his body until the baby seahorses are old enough to be released. As with any child, it is smell which keeps the young close to the parent. It is also the sense of smell which guides the salmon back to its spawning ground. Not once pausing to eat, the salmon steadily loses strength as it swims upstream. Many will die. (music) As the courage to breed gets stronger, the fish battles to conquer any obstacle, to leap any barrier.

It has no fear of hurrying itself clear of the the water in its frenzy risking its own life. But there are less dangerous fish out of water stories. Mud skippers love to play on land, using their fins as tiny legs, chasing each other across mudflats and catching insects. Walking catfish can stay out of water for up to 12 hours, covering over half a mile on land. While the Amazon Arowana will leap higher than a man to catch its prey. But none of these can match the salmon in power as it fights its way upstream, evading predators as it goes. (music and water) The salmon has completed its journey and now will breed, the female digging out a hollow

where the two trappers lie together. Of the three to five thousand eggs orginally laid, only one or two salmon will complete the marathon journey back to their breeding grounds. After spawning, many of these adults will drift exhausted downstream to die. But their eggs will hatch, and the lifecycle begins anew - like Pisces rebirth. The fish echoes our own birth. Our earliest living ancestor, ruler of a world greater than our world, and still far beyond our reach.(music and credits) Presentation of this program was made possible by the Corporation for Public Broadcasting and biannual

financial support from viewers like you. To order a video cassette of this eyewitness episode, call PBS video at 1-800-828-4PBS. Or write to the address on the screen. This is PBS. The modern photographic techniques used in the eye witness series bring the animal world to life on the pages of eyewitness natural world. Companion book to the eyewitness series, eyewitness natural world is published by Dorling Kindersley. The price is $29.95 plus $5.95 shipping and handling. To order this colorful and informative visual guide, call 1-800-440- 2651. Credit cards are accepted.