fishes and fishermans

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fishes and fishermans

  1. 1. 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 andgudgeon) 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
  2. 2. Many animals that live in water are called fish. Perch, crayfish, cuttlefish, jellyfish, starfish, and even whales and dolphins all live in water. Yet, of these animals, only the perch is a true fish. Whales and dolphins are warm-blooded mammals. The others belong to the great group of animals without backbones, called invertebrates.
  3. 3. 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.
  4. 4. Most fish exchange gases using gills on either side of the pharynx. Gills consist of threadlike structures called filaments. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. In some fish, capillary blood flows in the opposite direction to the water, causing countercurrent exchange. The gills push the oxygen-poor water out through openings in the sides of the pharynx. Some fish, like sharks and lampreys, possess multiple gill openings. However, bony fish have a single gill opening on each side. This opening is hidden beneath a protective bony cover called an operculum.
  5. 5. Early fish from the fossil record are represented by a group of small, jawless, armored fish known as Ostracoderms. Jawless fish lineages are mostly extinct. An extant clade, the Lampreys may approximate ancient pre-jawed fish. The first jaws are found inPlacodermi fossils. The diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. Fish may have evolved from a creature similar to a coral- like Sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the larval form into adulthood (as some sea squirts do today), although perhaps the reverse is the case.
  6. 6. Fishing is the activity of trying to catch fish. Fish are normally caught in the wild. Techniques for catching fish includehand gathering, spearing, netting, angling and trapping. The term fishing may be applied to catching other aquatic animals such as molluscs, cephalopods, crustaceans, . The term is not normally applied to catching farmed fish, or to aquatic mammals, such as whales, where the term whaling is more appropriate.
  7. 7. According to FAO statistics, the total number of commercial fishermen and fish farmers is estimated to be 38 million. fisheries and aquaculture provide direct and indirect employment to over 500 million people. In 2005, the worldwide per capita consumption of fish captured from wild fisheries was 14.4 kilograms, with an additional 7.4 kilograms harvested fromfish farms. In addition to providing food, modern fishing is also a recreational pastime.
  8. 8. There are many fishing techniques and tactics for catching fish. The term can also be applied to methods for catching other aquatic animals such as molluscs (shellfish, squid, octopus) and edible marine invertebrates. Fishing techniques include hand gathering, spearfishing, netting, angling and trapping. Recreational, commercial and artisanal fishers use different techniques, and also, sometimes, the same techniques. Recreational fishers fish for pleasure or sport, while commercial fishers fish for profit. Artisanal fishers use traditional, low-tech methods, for survival in third-world countries, and as a cultural heritage in other countries. Mostly, recreational fishers use angling methods and commercial fishers use netting methods. There is an intricate link between various fishing techniques and knowledge about the fish and their behaviour including migration,foraging and habitat. The effective use of fishing techniques often depends on this additional knowledge. Some fishermen follow fishing folklores which claim that fish feeding patterns are influenced by the position of the sun and the moon.

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