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Fish

A fish is a poikilothermic (cold-blooded) water-dwelling vertebrate with gills. There are over 27,000 species of fish, making them the most diverse group of vertebrates. more...

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Taxonomically, fish are a paraphyletic group whose exact relationships are much debated; a common division is into the jawless fish (class Agnatha, 75 species including lampreys and hagfish), the cartilaginous fish (class Chondrichthyes, 800 species including sharks and rays), with the remainder classed as bony fish (class Osteichthyes).

Fish come in different sizes, from the 14m (45 ft) whale shark to a 7 mm (just over 1/4 of an inch) long stout infantfish. Many types of aquatic animals named "fish", such as jellyfish and cuttlefish, are not true fish. Other sea dwelling creatures, like dolphins, are actually mammals.

Certain species of fish maintain elevated body temperatures to varying degrees. Endothermic teleosts (bony fishes) are all in the suborder Scombroidei and include the billfishes, tunas, and one species of "primitive" mackerel (Gasterochisma melampus). All sharks in the family Lamnidae – shortfin mako, long fin mako, white, porbeagle, and salmon shark – are known to have the capacity for endothermy, and evidence suggests the trait exists in family Alopiidae (thresher sharks). The degree of endothermy varies from the billfish, which warm only their eyes and brain, to bluefin tuna and porbeagle sharks who maintain body temperatures elevated in excess of 20 °C above ambient water temperatures. See also gigantothermy. Endothermy, though metabolically costly, is thought to provide advantages such as increased contractile force of muscles, higher rates of central nervous system processing, and higher rates of digestion.

Fish ecology

Fish can be found in almost all large bodies of water in salt or brackish or fresh water, at depths from just below the surface to several thousand meters. However, hyper-saline lakes like the Great Salt Lake do not support fishes. Some species of fish have been specially bred to be kept and displayed in an aquarium, and can survive in the home environment.

Catching fish for the purpose of food or sport is known as fishing. The annual yield from all fisheries worldwide is about 100 million tonnes. Overfishing is a threat to many species of fish. On May 15, 2003, the journal Nature reported that all large oceanic fish species worldwide had been so systematically over caught that fewer than 10% of 1950 levels remained. Particularly imperiled were sharks, Atlantic cod, Bluefin tuna, and Pacific sardines. The authors recommended immediate drastic cutbacks in fish catches and reservation of ocean habitats worldwide.

Note on usage: "fish" vs. "fishes"

"Fishes" is the proper English plural form of "fish" that biologists use when speaking about two or more fish species, as in "There are over 25,000 fishes in the world" (meaning that there are over 25,000 fish species in the world). When speaking of two or more individual fish organisms, then the word "fish" is used, as in "There are several million fish of the species Gadus morhua" (meaning that G. morhua comprises several million individuals). To see both in action, consider the statement "There are twelve fish in this aquarium, representing five fishes" (meaning that the aquarium contains twelve individuals, some of the same species and some of different species, for a total of five species). The usage of the two words is similar to that of the words "people" and "peoples".

Read more at Wikipedia.org


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10+1 Fire Red Cherry - Freshwater Neocaridina Aquarium Shrimp. Live Guarantee10+1 Fire Red Cherry - Freshwater Neocaridina Aquarium Shrimp. Live Guarantee $32.95 Aquaneat Led Aquarium Light Multi-Color Full Spec Marine Fowlr 12 20 24 30 36 48Aquaneat Led Aquarium Light Multi-Color Full Spec Marine Fowlr 12 20 24 30 36 48 $10.39 to
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Prices current as of last update, 12/02/21 10:57pm.

See also...
Aquarium Coral, Fish
Aquarium Decorations, Fish
Aquarium Lighting, Fish
Aquarium Meters, Regulators, Fish
Aquarium Stands, Fish
Aquariums & Bowls, Fish
Cleaning & Water Treatments, Fish
Crabs, Snails & Algae Eaters, Fish
Filtration & Heating, Fish
Fish Food, Fish
Live Aquarium Plants, Fish
Live Aquarium Rock, Fish
Other Fish Supplies, Fish
Refractometers, Fish
Tropical Fish, Fish

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