Fish
| 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 specific taxon (superclass, class, subclass, etc.) is presented in the image above. Another more detailed taxonomic scheme is offered by Benton (2004), in his textVertebrate Paleontology, of which the following was derived:
- SUBPHYLUM VERTEBRATA
- Class 'Agnatha' (paraphyletic)
- Subclass †Conodonta
- Subclass Petromyzontidae (lampreys)
- Subclass †Pteraspidomorphi
- Order †Thelodonti
- Order †Anaspida
- Subclass unnamed
- Order †Galeaspida
- Order †Pituriaspida
- Order †Osteostraci
- Infraphylum Gnathostomata (jawed vertebrates)
- Class †Placodermi
- Class Chondrichthyes (cartilaginous fish)
- Class †Acanthodii
- Class Osteichthyes (bony fish)
- Subclass Actinopterygii (ray-finned fish)
- Subclass Sarcopterygii (lobe-finned fish)
- Order Actinistia (coelacanths)
- Superclass Tetrapoda (four-limbed vertebrates)
- Class 'Agnatha' (paraphyletic)
Fish and humans
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. [1] 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.
Notes: "is impossible to overstate the importance of fish to human populations around the world. Throughout history, humans have used fish protein as a food source, with wild caught fish providing the bulk of fish protein. Fish have also been farmed in large quantities for more than 2000 years in China. Recent advances in fish farming (see Aquaculture), especially with some African cichlids (see Tilapia), have alleviated hunger in many parts of the world. In industrialized countries, farm-raised fish provide relief for overfished stocks of wild fish. Fish also have served as a source of recreational pleasure for many people. The catches from sports fisheries (see Fishing) are far larger than commercial catches from most freshwaters and in marine waters close to large population centers. Aquariums provide an intimate acquaintance with the aquatic world. More than 20 million home aquariums are kept in the United States alone. Among the many fish kept in aquariums, the most common are minnows, characins, and cichlids.
Some fishes may be dangerous to humans, although in most cases the danger is easily avoided. The stonefish is one of the most venomous vertebrates known, with enough toxin in the sharp dorsal spines to kill an adult human that steps on one (see Rockfish). The toxin of the pufferfish, or fugu, is deadly when eaten. Sharks have perhaps the worst but least deserved reputation for aggressiveness, for only a few of the species have been known to attack humans. Many larger fish when provoked are capable of inflicting wounds on humans. For example, moray eels, as sinister as they appear, do not go out of their way to attack humans, but will bite if provoked.
- The fish outline is a logical symbol for the early Christian church to adopt. Fish play a major role in the gospels. For example:
Mark 1:17: "Come after Me, and I will make you become fishers of men." Matthew 12:40: "...Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth." Matthew 14:17: "And they said to Him, 'We have here only five loaves and two fish.'" Luke 5:6: "And when they had done this, they caught a great number of fish, and their net was breaking." Luke 24:42: "So they gave Him a piece of a broiled fish and some honeycomb." John 21:6: "And He said to them, 'Cast the net on the right side of the boat, and you will find some.' So they cast, and now they were not able to draw it in because of the multitude of fish." 1 Corinthians 15:39: "All flesh is not the same flesh, but there is one kind of flesh of men, another flesh of beasts, another of fish, and another of birds."
Some Christians believe that a second link between their religion and the fish symbol is seen in the Greek word for fish (ichthus, spelled: Iota Chi Theta Upsilon Sigma). That is an acrostic which has many translations in English. The most popular appears to be "Jesus Christ, Son of God, Savior" 16 [Iesous (Jesus) CHristos (Christ) THeou (God) Uiou (Son) Soter (Savior)]. Alternate meanings (in order of decreasing popularity on the Internet) are:
"Jesus Christ, God's Son, Savior." "Jesus Christ, of God, the Son, the Savior" "Jesus Christ, the Son of God, Savior." "Jesus Christ, God's Son, our Savior" "Jesus Christ God Son Savior"
An acrostic is an "arrangement of words in which the first letter of each line ordinarily combines with others to form a word or words or the alphabet."
Threatened Fish
Humans are far more dangerous to fish than fish are to humans. Sharks kill about 30 people per year, while an estimated 700,000 metric tons of sharks are harvested or killed by people each year. Several species of sharks, including the great white, have been greatly overfished. Sharks are particularly susceptible to overfishing because most species need many years to grow to reproductive maturity.
Many stocks of wild fish have been harvested beyond their natural capacity to sustain their populations. Most recently, the collapse of the cod fishery in the Northwest Atlantic has heightened concerns over our ability to responsibly manage natural marine resources. Since the closing of those commercial fishing grounds, evidence is mounting that the fish populations are beginning to recover, although the recovery may take decades. Stocks of fish, like the bluefin tuna, that cross international borders or are found on the high seas are of special concern because they are particularly difficult to manage. Even large marine stocks once thought immune to the effects of overfishing, like the Pacific sardine and the Peruvian anchovy, have declined dramatically. In spite of these problems, fisheries can be successfully managed to reduce the effects of previous overfishing and to prevent further abuse. Proper management requires timely and accurate data on fish populations and harvest, as well as the ability to strictly enforce the protection of vulnerable fish stocks.
The most seriously threatened fishes are found in freshwaters of the world, especially in the environmentally sensitive and industrialized areas of the northern hemisphere. Many unique freshwater species are found only in a small area because of the isolation by land barriers. Thus, water pollution or habitat destruction in streams can be devastating to fish populations or even entire species. With increasing human populations, the effects are bound to intensify unless preventive actions are undertaken. Fortunately, significant advances in our knowledge of the effects of pollutants and habitat change have improved habitat restoration and pollution control."
Fishes are an important source of food in many cultures. Other water-dwelling animals such as mollusks, crustaceans, and shellfish are often called "fish" when used as food. For more details, see Fish (food).
See also
- Animal
- Aquarium
- Deep sea fish
- Fish anatomy
- Fish farming
- Fish migration
- Fish (singer)
- Fishing
- Ichthyology (the study of fish)
- List of fish families
- List of fish common names
- List of freshwater aquarium fish species
- Marine aquarium fish species
- Fishing Light Attractors
- Oily fish
- Ostracoderm - the first fishes
- Prehistoric fish
- Shoal - the collective noun for fish (also school)
- White fish
External links
- 70South - information on Antarctic fish
- A World of Fish Species information and fish care
- Fish database (FishBase)
- Join Ray Mullet in the Fish Olympics!
- Project for children - build a fish mobile with a behavior
- Fish Keeping
- Site with one of the largest fish databases in the world
- Reelinthefish.net | Interview with Dr James K. Oliver, Reefbase Scientist
- Fishy.UsArticles & Particles
- Saltwater & Freshwater Forums
- Your Fish Tank's Friend
- Fish and Seafood RecipesCooking With Fish
- Reef aquarium community and learning center
- German Educator in Fisheries, Specialist in Fancy Goldfish and Fishhealth, with Forum and large Picture-Gallery
- [2]Interesting fish game.
- Fish Aquarium simulator for mac.
- The Sushi FAQ - (the alt.food.sushi Usenet group FAQ) at SushiFAQ.com
- The Sushi Otaku Blog
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