fish

Member of vertebrate fish is poikilotermik (cold-blooded) that live in water and breathe with gills. Fish are vertebrate group with the most diverse species number more than 27,000 worldwide. Taxonomically, fish are a paraphyletic group whose relationships are much debated; fish usually divided into jawless fish (class Agnatha, 75 species including lampreys and hagfish), cartilaginous fish (class Chondrichthyes, 800 species including sharks and rays), and the rest classified as hard bony fish (class Osteichthyes). Fish in various regional languages ​​called iwak (jv, bjn), jukut (VKT).
 

Fish come in different sizes, ranging from whale sharks measuring 14 meters (45 ft) to stout infantfish size is only 7 mm (approximately 1/4 inch). There are some aquatic animals that are often regarded as the "fish", such as whales, fish and squid mermaid, which is not classified as a fish.

Classification

Fish is parafiletik group: this means, each class containing all fish will also cover non-fish tetrapod. On this basis, grouping like Pisces classes, as in the past, no longer fit for use.

Here are the units that includes all vertebrates commonly referred to as fish:

   Subclass Pteraspidomorphi (primitive jawed fish did not)
         class Thelodonti
         class Anaspida
         (no status) Cephalaspidomorphi (primitive jawed fish did not)
             (no status) Hyperoartia
                 Petromyzontidae (lamprey)
         class Galeaspida
         class Pituriaspida
         class Osteostraci

 
  Infrafilum Gnathostomata (jawed vertebrates)
         Placodermi class (armored fishes, extinct)
         Class Chondrichthyes (cartilaginous fishes: sharks, rays)
         Acanthodii class (spiny sharks, extinct)

  Superclass Osteichthyes (bony fishes true: covers almost all important fish present)
         Class Actinopterygii (finned fish fan)
         Class Sarcopterygii (fleshy fin fish / lobe finned fish)
             Subclass Coelacanthimorpha (coelacanth)
             Subclass Dipnoi (lungfish)

fish ecology

Fish can be found in almost all of the "puddle" of water is a good sized freshwater, brackish water or salt water at varying depths, from near surface to several thousand feet below the surface. However, hyper-saline lakes such as the Great Salt Lake can not support fish. There are several species of farmed fish to be maintained to be exhibited in the aquarium.

Fish is an important food source. Other aquatic animals, such as mollusks and crustaceans as well as fish sometimes considered when used as a food source. Catch fish for the purpose of food or sport is known as fishing. Results fishing world each year amounted to about 100 million tonnes.

Overfishing is a term in the English language to explain overfishing. This phenomenon is a threat to various species of fish. On May 15, 2003, the journal Nature reported that all species of large marine fish have been caught up in a systematic excess amount is less than 10% of the amount present in 1950. The author of the journal article suggests a drastic reduction in fishing and marine habitats reservations worldwide.