Fish And Their Characteristics (1961)

thank you have you ever heard the saying like a fish out of water a fish must stay in the water to stay alive without special breathing equipment a man could not remain alive underwater for any length of time fish are able to live underwater because they have special adaptations such as fins and gills which we'll see as we observe fish underwater we can find fish in almost all of the fresh water and saltwater lakes and oceans in the world some spend their lives in a relatively small area living among the rocks and crevices where they were hatched others roam or migrate far from their birthplace and return only when it is time for them to reproduce there are many kinds of fish some are quite small While others such as this grouper are quite large all fish have more or less streamlined bodies even though they may have very different shapes all fish have fins which they use for balancing and guiding their streamlined bodies through the water fish differ greatly in their color and markings sometimes their markings protect fish by means of camouflage making it hard for their enemies to see them can you see the Spotted fish at the left near The Rock this is a flounder his coloring and his habit of beating the sand around him as he settles on the bottom make him very hard to see only his eye shows now many fish feed on smaller fish some fish eat other kinds of animals that live in the water such as this crab others feed on many kinds of plants found in the water an important food for fish are the tiny forms of life called plankton this is plankton under a microscope Plankton is made up of microscopic plants and animals that float near the surface of the ocean we have been seeing some of the many kinds of fish that live only in the saltwater oceans and seas of the world many other kinds of fish however live only in freshwater streams and lakes we can learn much about all types of fish by studying a very common freshwater fish the perch although we have seen that fish are different from one another most fish resemble the perch in general structure like all true fish the perch has a backbone fish have two pairs of fins the pectoral fins and the ventral fins besides these the perch has Dorsal fins on the back an anal fin and a tail fin so an important characteristic of all fish are fins notice how the two pectoral fins steer the perch and help him to keep his balance the tail and tail fin push the fish through the water a fish's eyes have no lids the water washes them free of dirt and keeps them moist to keep at a certain level in the water the perch and many other fish have a swim bladder changing the amount of air-like gases in the bladder helps the fish rise in the water or sink in some fish the swim bladder is partly used for breathing but fish breathe chiefly with their gills on each side under the Gill cover there are four gills each consists of a bony Arch on the edge of each Gill are gill filaments the filaments are bathed with water that passes through the mouth and out through the gills fish breathe oxygen by taking it out of the water in which it is dissolved oxygen in the water is absorbed in the blood vessels in the gills and then into the circulatory system waste carbon dioxide gas is thrown off from the gills into the water so gills for breathing are another important characteristic of all fish a third characteristic is scales most fish including the perch have a body covering of scales the scales are overlapped and embedded in the skin however several kinds of fish including the catfish have a body covering of smooth skin without scales the shark skin is covered with small spiny plates that are not true scales the shark is not a true fish a fourth characteristic of all fish is that they are cold-blooded this means that the body temperature changes with the water temperature a fish in Winter becomes sluggish and inactive it lives through the winter on the bottom below the ice that covers the cold water in the spring fish lay their eggs this is called spawning this female trout has laid her eggs in a shallow stream after the female lays her eggs they are fertilized by the male the female may lay thousands of eggs at one time although fish lay great numbers of eggs their enemies usually eat most of them as well as the young after they hatch in the case of the trout and other fish the yolk Sac which provides food for the developing fish while in the egg remains attached to the young the yolk sack will soon be absorbed as the young fish grows most fish lay eggs some like the bluegill prepare a sort of nest and guard the eggs until they hatch some tropical fish such as the Siamese fighting fish build a bubble nest on the surface of the water which we are seeing from Below in some fish such as the guppy the young develop inside the female's body and are born alive some fish such as the salmon leave the salt water of the ocean and make extraordinary trips to certain freshwater streams to lay their eggs they swim upstream against the current to find the place where they were born the salmon show great strength swimming against Rapids and waterfalls even though they may be pushed back again and again by the current now that we have seen the characteristics of fish we will be able to recognize underwater animals that are not fish including the great group of animals without backbones called invertebrates the crab is an invertebrate it is not a fish because it does not have such things as fins or scales even though this invertebrate is called a starfish it is not a fish it does not have the structures that are characteristic of fish many of the underwater invertebrates such as this sea anemone provide food for the true fish we have seen many kinds of fish are an important source of food for man in heavily populated countries such as Japan people depend on fish for survival as the Earth's population increases fish will become an even more important source of food in some places in our country fish have been removed faster than they could be naturally replaced the conservation program for fish includes fish hatcheries where young fish are raised to restock streams and lakes we are able to make better use of fish as a natural resource as we learn more about them about the many different kinds of fish and how they live how they reproduce and grow [Music] and what they feed upon [Music] these are fish the vertebrates that have fins gills scales and are cold-blooded these are the special characteristics of fish the most familiar of the groups of animals adapted for Life underwater [Music]