Difference between revisions of "Fish" - New World Encyclopedia
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==Fish and humans== | ==Fish and humans== | ||
| − | Throughout history, humans have utilized fish as a food source. | + | Throughout history, humans have utilized fish as a food source. Historically and today, most fish protein has come by means of catching wild fish. However, [[aquaculture]], or fish farming, which has been practiced for 2000 years in China, is becoming increasingly important. Overall, about one-sixth of the world's protein is estimated to be provided by fish. That proportion is considerably elevated in some developing nations and regions heavily dependent on the sea. In a similar manner, fish have been tied to trade. One of the world’s longest lasting trade histories is the trade of dry cod from the Lofoten area in northern Norway to the southern parts of Europe. This trade in cod has been going on for more than 1000 years. |
| − | Fish also caught for sport. | + | Fish also caught for sport. Indeed, in many aquatic environments today, including most freshwaters, there are more fish caught for sport than via commercial fisheries. |
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| − | + | Catching fish for the purpose of [[food]] or [[sport]] is known as [[fishing]], while the organized effort by humans to catch fish is called a fishery. Fisheries are a huge global business and provide income for millions of people. The annual [[yield]] from all [[fishery|fisheries]] worldwide is about 100 [[million]] tons, with popular species including herring, cod, anchovy, tuna, flounder, and salmon. However, the term fishery is broad enough to include more organism than just fish, such as [[mollusk]]s, [[crustacean]]s, and [[shellfish]], which are often called "fish" when used as food. | |
| − | + | Another recreation use of fish is the popular hobby of keeping fish in aquariums in homes, offices, or for public display. There are about 60 million aquarium enthusiasts worldwide. | |
| + | Because of the popularity of fish for food, sport, and hobby, [[overfishing]] is a threat to many species of fish. On [[May 15]] [[2003]], the journal ''[[Nature (journal)|Nature]]'' reported that all large [[ocean]]ic fish species worldwide had been so systematically over caught that fewer than 10% of 1950 levels remained. Particularly imperiled were [[shark]]s, Atlantic [[cod]], [[Bluefin tuna]], and Pacific [[sardine]]s. The authors recommended immediate drastic cutbacks in fish catches and reservation of ocean [[habitat (ecology)|habitats]] worldwide. | ||
| − | Some fish | + | Some fish pose dangers to humans. Although the sharks may be among the most feared, there are actually few shark species that are known to attack humans. The largest sharks, the whale shark and basking shark, are actually plankton feeders. The International Shark Attack File reports there are only about 10-15 deaths each year worldwide. This compares to about 1,000 deaths annually from crocodiles and 60,000 from snakebites. The pufferfish, often better by the Japanese name Fugu, poses risks because the fish contains a highly toxic poison in the internal organs. Despite this, it is considered a delicacy in Japan, and needs to be very specially prepared to be safe for eating. Every year a number of people die from consuming this fish. The stonefish has spines that release a venomous toxin, and can be fatal to humans if not treated promptly. Barracudas, sea bass, moray eels, and stingrays are among others that pose risks to humans. |
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| + | Fish are also prominent in human religious culture, particularly Christianity. Fish and fishing play a significant role in the gospels of the New Testament, and the outline of a fish is often a symbol used by the Christian chruch. Fishing is a widely used metaphor, such as when Jesus is recorded as stating, "Follow me, and I will make you fishers of men" (Matthew 4:19). Some Christians see the Greek word for fish (ichthus, spelled Iota Chi Theta Upsilon Sigma) as an acrostic (where the first letter of a series of words forms a word) for Jesus. That is, alternative means are given such as "Jesus Christ, Son of God, Savior" 16 [Iesous (Jesus) CHristos (Christ) THeou (God) Uiou (Son) Soter (Savior)]. | ||
[[Image:bbas2.jpg|thumb|''Centropristis striata'']] | [[Image:bbas2.jpg|thumb|''Centropristis striata'']] | ||
Revision as of 02:55, 23 March 2006
| Fish | ||||||||
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 Atlantic herring, Clupea harengus The most abundant species of fish in the world. | ||||||||
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Agnatha (jawless vertebrates)
Gnathostomata (jawed vertebrates)
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A fish is a poikilothermic (cold-blooded), water-dwelling vertebrate with gills throughout life and limbs, if present, in the form of fins. Poikilothermic refers to the fact that the internal temperatures of fish vary, often matching the ambient temperature of the environment.
There are over 27,000 known extant (living) species of fish, making them the most diverse group of vertebrates, with more than one-half of the total vertebrate species. A heterogeneous assemblage, modern fish are conventionally considered to be divided into the jawless fish (class or superclass Agnatha, about 75 species including lampreys and hagfish), the cartilaginous fish (class Chondrichthyes, about 800 species including sharks and rays), and the bony fish (class Osteichthyes), with over 26,000 species. Some individuals use the term fish only when refering to the jawed bony fish, and do not include Agnatha and Chondrichthyes.
Unification aspects Fish an human, religion, culture, exploitation
Terminology: "fish" vs. "fishes"
Both "fish" and "fishes" are acceptable plurals, and examples of both forms are readily found in publications. Examples of the later include Nelson's Fishes of the World, 3rd Edition (1994), and the Guideliness for use of fishes in field research (1988) by the American Society of Ichthyologists and Herpetologists, the American Fisheries Society, and the American Institute of Fisheries Research Biologists. Examples of the use of fish as the plural are quite common in popular literature.
Although both plural forms are acceptable, a common preference among [[biology}biologists]] is to use the term "fishes" when speaking about two or more kinds of fish (species), and the term "fish" when referring to two or more individual fish organisms. For example, the publication guidelines of the American Fisheries Society (2006) offers a preference for "fishes" as a synonym for "species of fish." Thus, if one would say "there are over 27,000 fishes in the world," one would be saying there are over 27,000 fish species in the world. If one would state "there are several million fish of the species Gadus morhua," one would be saying that G. morhua comprises several million individuals. The usage of the two words is similar to that of the words "people" and "peoples". Of course, languages change over time and one may see a trend in the use of these terms as well.
Characteristics of fish
Fish range in size from the 14m (45 ft) whale shark to a 7 mm (just over 1/4 of an inch) long stout infantfish and the 13 mm Philippine goby. Many types of aquatic animals named "fish", such as jellyfish, starfish, and cuttlefish, are not true fish. A number of sea dwelling creatures, like dolphins and whales, are actually mammals.
Hagfish, while generally classified in Agnatha ("jawless") and as fish, actually lack vertebrae. For this reason, hagfish, which are also commonly known as "slime eels," are sometimes not considered to be fish. The other living member of Agnatha, the lamprey, has primitive vertebrae made of cartilage. Hagish are a staple food in Korea. They are classified in the order Myxini and the family Myxinidae). Hagfish and lamprey have slimy skin without scales or plates. Both have a notochord that remains throughout life; circular, jawless mouths; and unpaired fins. Hagfish are found in the oceans and lampreys are found in both freshwater and ocean environments. Most lampreys are parasitic.
Fish belonging to the class Chondrichthyes are distinguished by cartilage skeletons, as opposed to skeletons of bone. They have moveable jaws and paired fins. Almost all of the Chondrichthyes—sharks, rays, and skates—are found in ocean environments.
Most fish species (about 95%) are placed in the class Osteichthyes (which some taxonomies consider a superclass). They have bony internal skeletons and skins with scales. These include coelacanths (lobe-finned fish), lungfish, and ray-finned fish. Coelacanths wer thought to have been extinct for many millions of years until one was caught by fishermen in 1938. Lungfish have lungs, as wel as gills. Ray-finned fish are what many people refer to when they use the term fish, as these are our most familiar fish, including bass, eels, and many sports fish. Ray-finned fish have fins that are supported by bones (rays).
While fish are poikilothermic in that they do not maintain constant internal temperatures and the temperature often mirrors the ambient temperature, certain species of fish maintain elevated body temperatures to varying degrees. These include teleosts (bony fishes) in the suborder Scombroidei and 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, and evidence suggests the trait exists in family Alopiidae (thresher sharks). The degree of being able to have elevated temperatures varies from the billfish, which warm only their eyes and brain, to bluefin tuna and porbeagle sharks who can elevate body temperatures in excess of 20 °C above ambient water temperatures. In many cases, this phenomena has been traced to heat exchange as warmer blood being returned to the gills in small veins runs parallel with colder, oxygenated blood in the arteries. This ability to have elevated temperatures allows fish to be active in colder waters and enhance swimming ability with the additional heat in the muscles. Most fish can survive only at a relatively small range of body temperatures, but may adjust their depth in large bodies of water in order to find preferable ranges.
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.
Classification
Fish are a very diverse assemblage, so much so that the term fish is itself more one of convenience than a taxonomic rank (Nelson 1994). It is used to designate a paraphyletic group, whereby the most recent common ancestor is included but not all descendants, with tetrapods (four-legged vertebrates, or descendants of four-legged vertebrates) being excluded. It is thus not surprising that different taxonomists may classify fish differently.
Vertebrates are generally classified into two groups, the Agnatha (jawless vertebrates) and the Gnathostomata (jawed vertebrates), with the later not only including fish with hinged jaws, but also amphibians, reptiles, birds, and mammals (the tetrapods). Most taxonomies consider Agnatha and Gnathostomata to be superclasses, although sometimes Agnatha is considered a class. In addition to including the modern day lampreys (Petromyzontiformes) and hagfish (Myxiniformes), the Agantha also includes several extinct orders. Within the Gnathostomata, several classes of fish are recognized, including the extant classes of Chondrichthyes (cartilaginous fish), and Osteichthyes (bony fish), although the later is sometimes considered a superclass. Within the Osteichthyes, two extant subclasses (or classes) are generally recognized, the Actinopterygii (ray-finned or spiny-finned fish) and the Sarcopterygii (lobe-finned fish). The coelacanths are generally considered within the Sacropterygii subclass. The Actinopterygii are also often divided into the Chondrostei and the Neopterygii, the latter of which includes the Teleostei (modern bony fishes), of which most fishes today are."
One general grouping of fish, without reference to the names of ranks of taxa (superclass, class, subclass, etc.) is presented in the image above. Another more detailed taxonomic scheme, with the rank names, is offered by Benton (2004), in his textVertebrate Paleontology, of which the following was derived:
- SUBPHYLUM VERTEBRATA
- Class 'Agnatha' (paraphyletic)
- Infraphylum Gnathostomata (jawed vertebrates)
- Class †Placodermi
- Class Chondrichthyes (cartilaginous fish)
- Subclass Elasmobrachii (sharks, rays, skates)
- Subclass Subterbranchialia
- Superorder Holocephali (chimaeras)
- Class †Acanthodii
- Class Osteichthyes (bony fish)
- Subclass Actinopterygii (ray-finned fish)
- Superdivision Chondrostei (sturgeons, paddlefish)
- Superdivision Neopterygii (teleosts—modern bony fish)
- Subclass Sarcopterygii (lobe-finned fish)
- Order Dipnoi (lungfish)
- Infraclass Crossopterygii
- Order Actinistia (coelacanths)
- Subclass Actinopterygii (ray-finned fish)
† = extinct (the group lacks any living members)
Fish and humans
Throughout history, humans have utilized fish as a food source. Historically and today, most fish protein has come by means of catching wild fish. However, aquaculture, or fish farming, which has been practiced for 2000 years in China, is becoming increasingly important. Overall, about one-sixth of the world's protein is estimated to be provided by fish. That proportion is considerably elevated in some developing nations and regions heavily dependent on the sea. In a similar manner, fish have been tied to trade. One of the world’s longest lasting trade histories is the trade of dry cod from the Lofoten area in northern Norway to the southern parts of Europe. This trade in cod has been going on for more than 1000 years.
Fish also caught for sport. Indeed, in many aquatic environments today, including most freshwaters, there are more fish caught for sport than via commercial fisheries.
Catching fish for the purpose of food or sport is known as fishing, while the organized effort by humans to catch fish is called a fishery. Fisheries are a huge global business and provide income for millions of people. The annual yield from all fisheries worldwide is about 100 million tons, with popular species including herring, cod, anchovy, tuna, flounder, and salmon. However, the term fishery is broad enough to include more organism than just fish, such as mollusks, crustaceans, and shellfish, which are often called "fish" when used as food.
Another recreation use of fish is the popular hobby of keeping fish in aquariums in homes, offices, or for public display. There are about 60 million aquarium enthusiasts worldwide.
Because of the popularity of fish for food, sport, and hobby, 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.
Some fish pose dangers to humans. Although the sharks may be among the most feared, there are actually few shark species that are known to attack humans. The largest sharks, the whale shark and basking shark, are actually plankton feeders. The International Shark Attack File reports there are only about 10-15 deaths each year worldwide. This compares to about 1,000 deaths annually from crocodiles and 60,000 from snakebites. The pufferfish, often better by the Japanese name Fugu, poses risks because the fish contains a highly toxic poison in the internal organs. Despite this, it is considered a delicacy in Japan, and needs to be very specially prepared to be safe for eating. Every year a number of people die from consuming this fish. The stonefish has spines that release a venomous toxin, and can be fatal to humans if not treated promptly. Barracudas, sea bass, moray eels, and stingrays are among others that pose risks to humans.
Fish are also prominent in human religious culture, particularly Christianity. Fish and fishing play a significant role in the gospels of the New Testament, and the outline of a fish is often a symbol used by the Christian chruch. Fishing is a widely used metaphor, such as when Jesus is recorded as stating, "Follow me, and I will make you fishers of men" (Matthew 4:19). Some Christians see the Greek word for fish (ichthus, spelled Iota Chi Theta Upsilon Sigma) as an acrostic (where the first letter of a series of words forms a word) for Jesus. That is, alternative means are given such as "Jesus Christ, Son of God, Savior" 16 [Iesous (Jesus) CHristos (Christ) THeou (God) Uiou (Son) Soter (Savior)].
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