Fish are cold-blooded animals, havefins and a backbone. There are about 22,000 species of fish that began evolvingaround 480 million years ago. The largemouth bass illustrated above the typicaltorpedo like (fusiform) shape associated with many fishes. A fish is any member of a paraphyletic (ancestral)group of organisms that consist of all gill-bearing aquatic craniate animalsthat lack limbs with digits.
Included in this definition are the livinghagfish, lampreys, and cartilaginous and bony fish, as well as various extinctrelated groups. Most fish are ectothermic (“cold-blooded”), allowing theirbody temperatures to vary as ambient temperatures change, though some of thelarge active swimmers like white shark and tuna can hold a higher coretemperature. Fishes are oldest aquatic vertebrates found all overthe globe. Nearly 500million years ago the first fish appeared on the earth. Today fishes make upthe largest group of vertebrates with 24,000species. Fishes have their habitats in lakes, streams, oceans, and estuaries.In 1991 it was estimated that 2546 species offish populated theworld. Out of which 969 belong to genera, 254 families, and 40 orders.
Around 80% of fish population around the globe wasrepresented by the Indian fishes. Fishes are capableof living in both fresh and marine water. Types offish Depending upon the habitats and characteristics there are avariety of fish available on the world.1. Fresh Water2. Tropical3. Marine4. Cold Water5.
AquariumFish1. Freshwater fishFishes that spent most of or all timeof living in fresh water bodies such as lakes and rivers in which the salinityis less than 0.05%. Theseenvironments differ from marine conditions in many ways, the most obvious beingthe difference in levels of salinity. To survive fresh water, the fish need arange of physiological adaptations. 41.24%of all known species of fish are found in fresh water. India is rich with inland freshwater fish,with about 940 species known from its rivers, lakes and estuaries.
Thisconstitutes about 38% of the Indian Ichthyofauna and are of considerableeconomic and scientific value. Of these about 500 species are primaryfreshwater fish with around 65% endemic, cloistered in the two hot spots ofIndia, the Western Ghats and the North East. However, threats to these faunaare aplenty, with urbanization, deforestation, habitat loss, pollution,over-harvesting, and culture of exotics. Some of them areIndian Major Carps- Rohu, Catla, Mrigal and bala sharks, betta fish, candirufish, gold fish, and oscur fish. 2.Marine fish Fishes that are capable of living inthe sea water are known as marine fish. About 15,000 species belong to themarine species.
Tropical climate is required for most of the marine fish tosurvive. Every species of the marine creature have their own appearance,environmental needs, nutritional requirements, reproduction capability, andcompatibility. Blue whale, dolphin, cuttle fish, jelly fish, loin fish and starfish are the major marine fish species.3.Tropical fishThese fishes require warm andtropical climate to survive. Both freshwater and saltwater species come under thiscategory. Because of their bright coloration they act a popular aquariumfishes.
Angel and gold fish are more famous for the aquarium environment.4.Coldwater fishColdwater fish, in the context ofaquariums, refers to fish species that prefer cooler water temperatures thantropical fish, typically below 20 °C (68 °F). Some examples are koi andgoldfish.
These species tend to grow more slowly and live longer than fish thatlive in warmer waters, and are generally felt to be easier to keep.5.Aquarium fishThe fishes which keep in aquaria fordisplay purpose in homes, hotels, exhibitions etc. refers to aquarium fishes.
Although a fish has to be always low growing and having small size. They may befrom all of the above types of fishes e.g.
Gold fish, Cat fish etc.Classificationof Fish based on characteristics (orScientific)Fish, the member of the AnimaliaKingdom is classified into Phylum Chordata and Vertebrata Subphylum. Fishes poses notochord, tubularnerve chord, and paired gills, segmentation of the body parts, post anal tail,ventral heart, and an endoskeleton to be the member of the Chordata. In orderto be a vertebrate, it poses backbone. This back bone supports and protects thespinal cord.All the species of the fish found inthe world are classified into the following three groups.
1. Agnatha – jawless fish2. Chrondrichthyes – cartilaginous fish3. Osteichthyes – bony fisha. Ray finned groupb. Lobe finned groupAbout 50species of Agnatha fish, 600 species ofChrondrichthyes fish and 30,000 species ofOsteichthyes fishare found in the world.
Most of the fishes in the bony group belong to the rayfinned group. According to the biologist there are about 70 fish orders are found in the world.Fish Orders- Sharks and rays;sturgeon and gars; herring-like fishes; trout and salmon; eels, minnows,suckers, and catfish; flying fish and relatives; cod-like fish; flatfish;seahorses and relatives; mullets, silversides, and barracuda; and mackerels andtunas are the main group of fishes.1. Agnatha- JawlessPhylum: chordateSubphylum: vertebrataAgnatha are jawless fish and lackpaired fins. They also lack the internal skeleton system.
They have a circulartooth mouth (cyclostomic) by which they bore the body of their victim and sucktheir blood. These areclassified in to two major types as Hagfish and Lampreys.Characteristicof AgnathaJaws are absent. Paired fins areabsent. Bony scales and skin plates were present in the ancient species but areabsent in the living species. Gill pouches are present.
They have seven or morepouches. Stomach is absent in the digestive system. E.g. Hagfish2.Chrondrichthyes- Cartilaginous fishPhylum: chordateSubphylum: vertebrata
