A fish is any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic (“cold-blooded”), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). At 32,000 species, fish exhibit greater species diversity than any other group of vertebrates.
Fish are an important resource for humans worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.
Because the term “fish” is defined negatively, and excludes the tetrapods (i.e., the amphibians, reptiles, birds and mammals) which descend from within the same ancestry, it is paraphyletic, and is not considered a proper grouping in systematic biology. The traditional term pisces (also ichthyes) is considered a typological, but not a phylogenetic classification.
The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods.
Tenualosa ilisha (ilish, hilsa, hilsa herring or hilsa shad) is a species of fish in the herring family (Clupeidae), and a popular food fish in South Asia.Other names include; Palla fish, Hilsha, Ellis, Ilish Bengali : ইলিশ Ilish Oriya: ଇଲିଶି Ilishii Sindhi: پلو مڇي Pallu Machhi Telugu: పులస andPulasa or Polasa. The ilish word is also used in India’s Assamese-,Bengali-, Oriya- and Telugu-speaking regions and in Pakistan’s Sindhprovince. In Gujarat it is known as either Modenn or Palva and the English word is Hilsa.
Catfishes (order Siluriformes) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat’s whiskers, catfish range in size and behavior from the heaviest and longest, the Mekong giant catfis from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores (species that eat dead material on the bottom), and even to a tiny paraditi species commonly called the candiru, Vandellia cirrhosa. There are armour-plated types and there are also naked types, neither having scales. Despite their name, not all catfish have prominent barbel. Members of the Siluriformes order are defined by features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corycoras, are important in the aquarium hobby . Many catfish are nocturna but others (many Archenipteridae) are crepuscular or diumal(most Loricaiidae or Callichthyidae for example).
Catla (Catla catla or Gibelion catla), also known as the major (Indian) carp, is an economically important South Asian freshwater fish in the carp family Cyprinidae. It is commonly found in rivers and lakes in northern Inkia, Nepalm Myanmar,Bangladesh and Pakistan.
Catla is a fish with large and broad head, a large protruding lower jaw and upturned mouth. It has large, greyish scales on dorsal side and whitish on belly.
Catla is a surface feeder and midwater feeder also. Adults feed on zooplankton but young ones on both zooplankton and phytoplankton.
The catla is the only member of its monotypic genus Catla, and is listed as Catla catla for instance in fish Base. Nevertheless Catalog of Fishes indicates Gibelion as the valid (senior) name of this genus.
Climbing perch, also called Walking Fish, (Anabas testudineus), small Asian freshwater fish of the family Anabantidae (order Perciformes) noted for its ability to live and walk about out of water. The climbing perch is an air-breathing labyrinth fish. Rather oblong, brownish or green, it grows to about 25 cm (10 inches). It lives in ponds and ditches and sometimes emerges for short periods, “walking” with a jerky motion, aided by its tail and by spines on the lower edges of its gill covers.