Why Do I Need an Exclusion Service? Wildlife Exclusion is a specialized profession much like a plumber or an electrician. With human development expanding, the native habitats of many species are being encroached upon. This limitation of natural resources is causing wildlife to venture into human territory. Fish protection objectives may vary widely with site and fisheries concerns. Possible fish protection objectives could be as follows: Exclusion of all fish from the diverted flow without regard for fish species, life stage, and size Exclusion of fish of a specific size or greater Exclusion of fish of specific species and size (recognizing.
Swimming among of other fishHead-on view of aKingdom:Phylum:Clade:Subphylum:Groups included† †included but traditionally excluded taxaFish are -bearing animals that lack with. They form a sister group to the, together forming the. Included in this definition are the living, and and as well as various extinct related groups. Emerged within, so they are fish as well.
However, traditionally fish are rendered by excluding the tetrapods (i.e., the, and which all descended from within the same ancestry). Because in this manner the term 'fish' is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces (also ichthyes) is considered a, but not a classification.The earliest organisms that can be classified as fish were soft-bodied that first appeared during the period. Although they lacked a, they possessed which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed that protected them from predators. The first fish with appeared in the period, after which many (such as ) became formidable marine predators rather than just the prey of.Most fish are ('cold-blooded'), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like and can hold a higher.Fish can communicate in their underwater environments through the use of acoustic communication.
Acoustic communication in fish involves the transmission of acoustic signals from one individual of a species to another. The production of sounds as a means of communication among fish is most often used in the context of feeding, aggression or courtship behaviour.
The sounds emitted by fish can vary depending on the species and stimulus involved. They can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.Fish are abundant in most bodies of water.
They can be found in nearly all aquatic environments, from high mountain streams (e.g., and ) to the and even depths of the deepest oceans (e.g., and ), although no species has yet been documented in the deepest 25% of the ocean. With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates.Fish are an important resource for humans worldwide, especially. Commercial and subsistence fishers hunt fish in (see fishing) or them in ponds or in cages in the ocean (see ).
They are also caught by, kept as pets, raised by, and exhibited in public. Fish have had a role in culture through the ages, serving as, religious symbols, and as the subjects of art, books and movies. Was a gigantic, 10-metre (33 ft) long of class Placodermi.Fish do not represent a group, and therefore the 'evolution of fish' is not studied as a single event.Early fish from the fossil record are represented by a group of small, jawless, armored fish known as. Jawless fish lineages are mostly extinct. An extant clade, the may approximate ancient pre-jawed fish. The first jaws are found in fossils. The diversity of jawed vertebrates may indicate the evolutionary advantage of a.
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, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have (as some sea squirts do today), although perhaps the reverse is the case.TaxonomyFish are a group: that is, any containing all fish also contains the, which are not fish. For this reason, groups such as the class Pisces seen in older reference works are no longer used in formal classifications. The psychedelic is one of only two animal species known to have blue colouring because of cellular pigment.The term 'fish' most precisely describes any non- (i.e. An animal with a skull and in most cases a backbone) that has throughout life and whose limbs, if any, are in the shape of fins. Unlike groupings such as birds or, fish are not a single but a collection of, including,. Indeed, lungfish and coelacanths are closer relatives of (such as, birds, etc.) than of other fish such as or sharks, so the of all fish is also an ancestor to tetrapods.
As paraphyletic groups are no longer recognised in modern, the use of the term 'fish' as a biological group must be avoided.Many types of commonly referred to as 'fish' are not fish in the sense given above; examples include,. In earlier times, even biologists did not make a distinction – sixteenth century natural historians classified also, whales, even, as well as a host of aquatic invertebrates, as fish. However, according to the definition above, all mammals, including like whales and dolphins, are not fish. In some contexts, especially in, the true fish are referred to as finfish (or fin fish) to distinguish them from these other animals.A typical fish is, has a body for rapid swimming, extracts oxygen from water using gills or uses an accessory breathing organ to breathe atmospheric oxygen, has two sets of paired fins, usually one or two (rarely three) dorsal fins, an anal fin, and a tail fin, has jaws, has skin that is usually covered with, and lays eggs.Each criterion has exceptions., and some species of show – they can heat their bodies significantly above ambient water temperature. Streamlining and swimming performance varies from fish such as, and that can cover 10–20 body-lengths per second to species such as and that swim no more than 0.5 body-lengths per second. Many groups of freshwater fish extract oxygen from the air as well as from the water using a variety of different structures. Have paired lungs similar to those of tetrapods, have a structure called the that performs a similar function, while many catfish, such as extract oxygen via the intestine or stomach.
Body shape and the arrangement of the fins is highly variable, covering such seemingly un-fishlike forms as,. Similarly, the surface of the skin may be naked (as in ), or covered with scales of a variety of different types usually defined as (typical of sharks and rays), (fossil lungfish and coelacanths), (various fossil fish but also living and ), and (these last two are found on most ). There are even fish that live mostly on land or lay their eggs on land near water. Feed and interact with one another on mudflats and go underwater to hide in their burrows. A single, of, has been called a true 'land fish' as this worm-like catfish strictly lives among waterlogged.
Many species live in, or and are popularly known as.Fish range in size from the huge 16-metre (52 ft) to the tiny 8-millimetre (0.3 in).Fish diversity is roughly divided equally between marine (oceanic) and ecosystems. In the constitute the center of diversity for marine fishes, whereas continental freshwater fishes are most diverse in large of, especially the, and basins. More than 5,600 fish species inhabit freshwaters alone, such that represent about 10% of all species on the Earth. Exceptionally rich sites in the Amazon basin, such as, can contain more freshwater fish species than occur in all of Europe. Anatomy and physiology.
See also: GillsMost fish exchange gases using on either side of the. Gills consist of threadlike structures called. Each filament contains a network that provides a large for exchanging. 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. The gills push the oxygen-poor water out through openings in the sides of the pharynx.
Some fish, like and, possess multiple gill openings. However, have a single gill opening on each side. This opening is hidden beneath a protective bony cover called an.Juvenile have external gills, a very primitive feature that they share with larval.Air breathing. Gills inside the head. The fish head is oriented snout-downwards, with the view looking towards the mouth.Fish from multiple groups can live out of the water for extended periods.
Such as the can live and move about on land for up to several days– or live in stagnant or otherwise oxygen depleted water. Many such fish can breathe air via a variety of mechanisms. The skin of may absorb oxygen directly. The of the may breathe air. Catfish of the families, and absorb air through their digestive tracts., with the exception of the, and have paired lungs similar to those of and must surface to gulp fresh air through the mouth and pass spent air out through the gills. And have a vascularized swim bladder that functions in the same way., and many breathe by passing air through the gut. Mudskippers breathe by absorbing oxygen across the skin (similar to frogs).
A number of fish have evolved so-called accessory breathing organs that extract oxygen from the air. Labyrinth fish (such as and ) have a above the gills that performs this function. A few other fish have structures resembling labyrinth organs in form and function, most notably, and the catfish family.Breathing air is primarily of use to fish that inhabit shallow, seasonally variable waters where the water's oxygen concentration may seasonally decline.
Fish dependent solely on dissolved oxygen, such as perch and, quickly suffocate, while air-breathers survive for much longer, in some cases in water that is little more than wet mud. At the most extreme, some air-breathing fish are able to survive in damp burrows for weeks without water, entering a state of (summertime hibernation) until water returns.Air breathing fish can be divided into obligate air breathers and facultative air breathers. Obligate air breathers, such as the, must breathe air periodically or they suffocate. Facultative air breathers, such as the catfish, only breathe air if they need to and will otherwise rely on their gills for oxygen.
Most air breathing fish are facultative air breathers that avoid the energetic cost of rising to the surface and the fitness cost of exposure to surface predators. Of a fish heartFish have a. The pumps the blood in a single loop throughout the body.
In most fish, the heart consists of four parts, including two chambers and an entrance and exit. The first part is the, a thin-walled sac that collects blood from the fish's before allowing it to flow to the second part, the, which is a large muscular chamber. The atrium serves as a one-way antechamber, sends blood to the third part,. The ventricle is another thick-walled, muscular chamber and it pumps the blood, first to the fourth part, a large tube, and then out of the heart.
The bulbus arteriosus connects to the, through which blood flows to the gills for oxygenation.DigestionJaws allow fish to eat a wide variety of food, including plants and other organisms. Fish ingest food through the mouth and break it down in the. In the stomach, food is further digested and, in many fish, processed in finger-shaped pouches called, which secrete digestive and absorb nutrients. Organs such as the and add enzymes and various chemicals as the food moves through the digestive tract. The intestine completes the process of digestion and nutrient absorption.ExcretionAs with many aquatic animals, most fish release their nitrogenous wastes as. Some of the wastes through the gills.
Blood wastes are by the.Saltwater fish tend to lose water because of. Their kidneys return water to the body. The reverse happens in: they tend to gain water osmotically.
Their kidneys produce dilute urine for excretion. Some fish have specially adapted kidneys that vary in function, allowing them to move from freshwater to saltwater.Scales. Dorsal view of the brain of the Central nervous systemFish typically have quite small brains relative to body size compared with other vertebrates, typically one-fifteenth the brain mass of a similarly sized bird or mammal. However, some fish have relatively large brains, most notably and, which have brains about as massive relative to body weight as birds and.Fish brains are divided into several regions.
At the front are the, a pair of structures that receive and process signals from the via the two. The olfactory lobes are very large in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed, the structural equivalent to the in. In fish the telencephalon is concerned mostly with. Together these structures form the forebrain.Connecting the forebrain to the midbrain is the (in the diagram, this structure is below the optic lobes and consequently not visible).
The diencephalon performs functions associated with. The lies just above the diencephalon.
This structure detects light, maintains rhythms, and controls color changes.The (or mesencephalon) contains the two. These are very large in species that hunt by sight, such as and.The hindbrain (or ) is particularly involved in swimming and balance. The cerebellum is a single-lobed structure that is typically the biggest part of the brain.
Hagfish and have relatively small cerebellae, while the cerebellum is massive and apparently involved in their.The brain stem (or ) is the brain's posterior. As well as controlling some muscles and body organs, in bony fish at least, the brain stem governs. Sense organsMost fish possess highly developed sense organs. Nearly all daylight fish have color vision that is at least as good as a human's (see ). Many fish also have chemoreceptors that are responsible for extraordinary senses of taste and smell.
Although they have ears, many fish may not hear very well. Most fish have sensitive receptors that form the, which detects gentle currents and vibrations, and senses the motion of nearby fish and prey. Some fish, such as catfish and sharks, have the, organs that detect weak electric currents on the order of millivolt. Other fish, like the South American electric fishes, can produce weak electric currents, which they use in navigation and social communication.Fish orient themselves using landmarks and may use mental maps based on multiple landmarks or symbols. Fish behavior in mazes reveals that they possess spatial memory and visual discrimination. Further information:Experiments done by William Tavolga provide evidence that fish have and fear responses.
For instance, in Tavolga's experiments, grunted when electrically shocked and over time they came to grunt at the mere sight of an electrode.In 2003, Scottish scientists at the and the Roslin Institute concluded that rainbow trout exhibit behaviors often associated with in other animals. And injected into the lips resulted in fish rocking their bodies and rubbing their lips along the sides and floors of their tanks, which the researchers concluded were attempts to relieve pain, similar to what mammals would do. Neurons fired in a pattern resembling human neuronal patterns.Professor James D. Rose of the claimed the study was flawed since it did not provide proof that fish possess 'conscious awareness, particularly a kind of awareness that is meaningfully like ours'. Rose argues that since fish brains are so different from human brains, fish are probably not conscious in the manner humans are, so that reactions similar to human reactions to pain instead have other causes. Rose had published a study a year earlier arguing that fish cannot feel pain because their brains lack a. However, animal behaviorist argues that fish could still have consciousness without a neocortex because 'different species can use different brain structures and systems to handle the same functions.'
Animal welfare advocates raise concerns about the possible of fish caused by angling. Some countries, such as Germany have banned specific types of fishing, and the British now formally prosecutes individuals who are cruel to fish. Muscular system.
Swim bladder of a rudd ( )Most fish move by alternately contracting paired sets of muscles on either side of the backbone. These contractions form S-shaped curves that move down the body. As each curve reaches the back fin, backward force is applied to the water, and in conjunction with the fins, moves the fish forward. The fish's fins function like an airplane's flaps. Fins also increase the tail's surface area, increasing speed.
The streamlined body of the fish decreases the amount of friction from the water. Since body tissue is denser than water, fish must compensate for the difference or they will sink.
Many bony fish have an internal organ called a that adjusts their buoyancy through manipulation of gases.EndothermyAlthough most fish are exclusively, there are exceptions. The only known bony fishes (infraclass ) that exhibit are in the suborder – which includes the, tunas, and the, a species of mackerel – and also the.
The opah, a, was demonstrated in 2015 to utilize 'whole-body endothermy', generating heat with its swimming muscles to warm its body while countercurrent exchange (as in respiration) minimizes heat loss. It is able to actively hunt prey such as squid and swim for long distances due to the ability to warm its entire body, including its heart, which is a trait typically found in only mammals and birds (in the form of ). In the cartilaginous fishes (class ), sharks of the families (porbeagle, mackerel, salmon, and great white sharks) and (thresher sharks) exhibit endothermy. The degree of endothermy varies from the billfishes, which warm only their eyes and brain, to the and the, which maintain body temperatures in excess of 20 °C (68 °F) above ambient water temperatures.Endothermy, though metabolically costly, is thought to provide advantages such as increased muscle strength, higher rates of central processing, and higher rates of.Reproductive system. : 1., 2., 3., 4. Pyloric caeca, 5., 6.Fish reproductive organs include. In most species, gonads are paired organs of similar size, which can be partially or totally fused.
There may also be a range of secondary organs that increase reproductive fitness.In terms of distribution, the structure of testes has two types: in the most common, spermatogonia occur all along the, while in fish they are confined to the portion of these structures. Fish can present cystic or semi-cystic in relation to the release phase of germ cells in cysts to the seminiferous tubules.Fish ovaries may be of three types: gymnovarian, secondary gymnovarian or cystovarian. In the first type, the are released directly into the cavity and then enter the, then through the and are eliminated. Secondary gymnovarian ovaries shed into the from which they go directly into the oviduct.
In the third type, the oocytes are conveyed to the exterior through the. Gymnovaries are the primitive condition found in,. Cystovaries characterize most teleosts, where the ovary lumen has continuity with the oviduct. Secondary gymnovaries are found in and a few other teleosts.development in teleosts fish varies according to the group, and the determination of oogenesis dynamics allows the understanding of maturation and fertilization processes. Changes in the, ooplasm, and the surrounding layers characterize the oocyte maturation process.Postovulatory are structures formed after oocyte release; they do not have function, present a wide irregular lumen, and are rapidly reabsorbed in a process involving the of follicular cells. A degenerative process called reabsorbs vitellogenic oocytes not spawned.
This process can also occur, but less frequently, in oocytes in other development stages.Some fish, like the, are, having both testes and ovaries either at different phases in their life cycle or, as in, have them simultaneously.Over 97% of all known fish are, that is, the eggs develop outside the mother's body. Examples of oviparous fish include,. In the majority of these species, fertilisation takes place outside the mother's body, with the male and female fish shedding their into the surrounding water. However, a few oviparous fish practice internal fertilization, with the male using some sort of to deliver sperm into the genital opening of the female, most notably the oviparous sharks, such as the, and oviparous rays, such as. In these cases, the male is equipped with a pair of modified fins known as.Marine fish can produce high numbers of eggs which are often released into the open water column. The eggs have an average diameter of 1 millimetre (0.039 in). French grunts – Haemulon flavolineatumThere are some species of fish that can produce sounds by rubbing or grinding their bones together.
These noises produced by bone-on-bone interactions are known as 'stridulatory sounds'.An example of this is seen in, a species commonly referred to as the 'French grunt fish', as it produces a grunting noise by grinding its teeth together.This behaviour is most pronounced when the is in distress situations. The grunts produced by this species of fishes generate a frequency of approximately 700 Hz, and last approximately 47 milliseconds.
The does not emit sounds with frequencies greater than 1000 Hz, and does not detect sounds that have frequencies greater than 1050 Hz.In a study conducted by Oliveira et al. (2014), the longsnout seahorse, was recorded producing two different categories of sounds; ‘clicks’ and ‘growls’. The sounds emitted by the are accomplished by rubbing their coronet bone across the grooved section of their neurocranium.‘Clicking’ sounds were found to be primarily produced during courtship and feeding, and the frequencies of clicks were within the range of 50 Hz-800 Hz. The frequencies were noted to be on the higher end of the range during spawning periods, when the female and male fishes were less than fifteen centimeters apart. Growl sounds were produced when the encountered stressful situations, such as handling by researchers.
The ‘growl’ sounds consist of a series of sound pulses and are emitted simultaneously with body vibrations. Non-stridulatory sound producing mechanisms. Oyster toadfishSome fish species create noise by engaging specialized muscles that contract and cause swimbladder vibrations.produce loud grunting sounds by contracting muscles located along the sides of their swim bladder, known as sonic musclesFemale and male toadfishes emit short-duration grunts, often as a fright response. In addition to short-duration grunts, male toadfishes produce “boat whistle calls”. These calls are longer in duration, lower in frequency, and are primarily used to attract mates.The sounds emitted by the O.
Tao have frequency range of 140 Hz to 260 Hz. The frequencies of the calls depend on the rate at which the sonic muscles contract.The red drum, produces drumming sounds by vibrating its swimbladder.
Vibrations are caused by the rapid contraction of sonic muscles that surround the dorsal aspect of the swimbladder. These vibrations result in repeated sounds with frequencies that range from 100 to 200 Hz. The can produce different calls depending on the stimuli involved.
The sounds created in courtship situations are different from those made during distressing events such as predatorial attacks. Unlike the males of the species, the females of this species don't produce sounds and lack sound-producing (sonic) muscles.
Main article:Like other animals, fish suffer from diseases and parasites. To prevent disease they have a variety of defenses. Non-specific defenses include the skin and scales, as well as the mucus layer secreted by the that traps and inhibits the growth of. If breach these defenses, fish can develop an that increases blood flow to the infected region and delivers that attempt to destroy pathogens. Specific defenses respond to particular pathogens recognised by the fish's body, i.e., an. In recent years, have become widely used in aquaculture and also with ornamental fish, for example vaccines in farmed and in.Some species use to remove external parasites.
The best known of these are the of the genus Labroides found on in the and oceans. These small fish maintain so-called 'cleaning stations' where other fish congregate and perform specific movements to attract the attention of the cleaners. Cleaning behaviors have been observed in a number of fish groups, including an interesting case between two cichlids of the same genus, the cleaner, and the much larger Etroplus suratensis. Immune systemImmune organs vary by type of fish.In the (lampreys and hagfish), true organs are absent.
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These fish rely on regions of within other organs to produce immune cells. For example, and are produced in the anterior kidney (or ) and some areas of the gut (where mature.) They resemble primitive in hagfish.(sharks and rays) have a more advanced immune system. They have three specialized organs that are unique to; the epigonal organs (lymphoid tissue similar to mammalian bone) that surround the gonads, the within the walls of their esophagus, and a in their intestine. These organs house typical immune cells (granulocytes, lymphocytes and plasma cells).
They also possess an identifiable and a well-developed (their most important immune organ) where various, plasma cells and macrophages develop and are stored.fish (sturgeons, paddlefish, and bichirs) possess a major site for the production of granulocytes within a mass that is associated with the (membranes surrounding the central nervous system.) Their heart is frequently covered with tissue that contains lymphocytes, and a small number of. The chondrostean kidney is an important organ; where erythrocytes, granulocytes, lymphocytes and macrophages develop.Like chondrostean fish, the major immune tissues of bony fish (or ) include the kidney (especially the anterior kidney), which houses many different immune cells.
In addition, teleost fish possess a thymus, spleen and scattered immune areas within mucosal tissues (e.g. In the skin, gills, gut and gonads).
Much like the mammalian immune system, teleost erythrocytes, neutrophils and granulocytes are believed to reside in the spleen whereas lymphocytes are the major cell type found in the thymus. In 2006, a lymphatic system similar to that in mammals was described in one species of teleost fish, the.
Although not confirmed as yet, this system presumably will be where naive (unstimulated) accumulate while waiting to encounter an.B and T lymphocytes bearing and, respectively, are found in all jawed fishes. Indeed, the as a whole in an ancestor of all jawed vertebrate. ConservationThe 2006 names 1,173 fish species that are threatened with extinction. Included are species such as,. Because fish live underwater they are more difficult to study than terrestrial animals and plants, and information about fish populations is often lacking. However, freshwater fish seem particularly threatened because they often live in relatively small water bodies. For example, the occupies only a single 3 by 6 metres (10 by 20 ft) pool.
Main article:Overfishing is a major threat to edible fish such as cod. Overfishing eventually causes (known as ) collapse because the survivors cannot produce enough young to replace those removed. Such commercial extinction does not mean that the species is extinct, merely that it can no longer sustain a fishery.One well-studied example of fishery collapse is the Sadinops sagax caerulues fishery off the California coast. From a 1937 peak of 790,000 long tons (800,000 t) the catch steadily declined to only 24,000 long tons (24,000 t) in 1968, after which the fishery was no longer economically viable.The main tension between and the is that the two groups have different views on the resiliency of fisheries to intensive fishing. In places such as Scotland, Newfoundland, and Alaska the is a major employer, so governments are predisposed to support it. On the other hand, scientists and conservationists push for stringent protection, warning that many stocks could be wiped out within fifty years.
Habitat destruction. See also:A key stress on both freshwater and marine ecosystems is habitat degradation including, the building of dams, removal of water for use by humans, and the introduction of species. An example of a fish that has become endangered because of habitat change is the, a North American freshwater fish that lives in rivers damaged by human activity.
Exotic speciesIntroduction of species has occurred in many habitats. One of the best studied examples is the introduction of into in the 1960s. Nile perch gradually exterminated the lake's 500 species. Some of them survive now in captive breeding programmes, but others are probably extinct., and are other examples of fish that have caused problems by being introduced into alien environments.Importance to humans Economic importance. These fish-farming ponds were created as a project in a rural village.Throughout history, humans have utilized. Historically and today, most fish has come by means of catching wild fish.
However, aquaculture, or fish farming, which has been practiced since about 3,500 BCE. In China, is becoming increasingly important in many nations. Overall, about one-sixth of the world's protein is estimated to be provided by fish. That proportion is considerably elevated in some and regions heavily dependent on the sea. In a similar manner, fish have been tied to trade.Catching fish for the purpose of food or sport is known as, while the organized effort by humans to catch fish is called a. Fisheries are a huge global business and provide income for millions of people. The annual yield from all fisheries worldwide is about 154 million tons, with popular species including,.
However, the term fishery is broadly applied, and includes more organisms than just fish, such as and, which are often called 'fish' when used as food.Recreation. Main articles:, andFish have been recognized as a source of beauty for almost as long as used for food, appearing in, being raised as in ponds, and displayed in in homes, offices, or public settings.Recreational fishing is fishing for pleasure or competition; it can be contrasted with, which is fishing for profit. The most common form of recreational fishing is done with a, and any one of a wide range of. Angling is a method of fishing, specifically the practice of catching fish by means of an 'angle' (hook). Anglers must select the right hook, accurately, and retrieve at the right speed while considering water and weather conditions, species, fish response, time of the day, and other factors.Culture.
Of as aFish themes have symbolic significance in many religions. In ancient, fish offerings were made to the gods from the very earliest times. Fish were also a major symbol of, the god of water. Fish frequently appear as filling motifs in from the ( c.
1531 BC) and (911–609 BC) periods. Starting during the ( c. 1155 BC) and lasting until the early (550–30 BC), healers and exorcists dressed in ritual garb resembling the bodies of fish. During the (312–63 BC), the legendary Babylonian, described by, was said to have dressed in the skin of a fish. Fish were sacred to the Syrian goddess and, during her festivals, only her priests were permitted to eat them. The is a Christian symbol of a fish signifying that the person who uses it is a Christian.In the, a work of Jewish literature probably written in the fourth century BC, the central figure, a named, is swallowed by a giant fish after being thrown overboard by the crew of the ship he is travelling on.
The fish later vomits Jonah out on shore after three days. This book was later included as part of the, or Christian, and a version of the story it contains is summarized in 37:139-148 of the. Used the, a symbol of a fish, to represent Jesus, because the Greek word for fish, ΙΧΘΥΣ Ichthys, could be used as an acronym for 'Ίησοῦς Χριστός, Θεοῦ Υἱός, Σωτήρ' (Iesous Christos, Theou Huios, Soter), meaning 'Jesus Christ, Son of God, Saviour'. The also refer to 'fishers of men'. In the of, the fish symbolize happiness as they have complete freedom of movement in the water.
Often drawn in the form of which are regarded in the Orient as sacred on account of their elegant beauty, size and life-span.Among the said to take the form of a fish are of the, of various ancient, the shark-gods of and of the Hindus. The symbol is based on a constellation of the, but there is also a second fish constellation in the night sky,.Fish feature prominently in art and literature, in movies such as and books such as. Large fish, particularly sharks, have frequently been the subject of and, most notably the novel, which spawned a series of films of the that in turn inspired similar films or parodies such as. Piranhas are shown in a similar light to sharks in films such as; however, contrary to popular belief, the is actually a generally timid scavenger species that is unlikely to harm humans.
Legends of half-human, half-fish have featured in folklore, including the stories of. Terminology Fish or fishesThough often used interchangeably, in biology these words have different meanings. Fish is used as a singular noun, or as a plural to describe multiple individuals from a single species. Fishes is used to describe different species or species groups. Thus a pond that contained a single species might be said to contain 120 fish. But if the pond contained a total of 120 fish from three different species, it would be said to contain three fishes.
The distinction is similar to that between people and peoples.True fish and finfish. In biology, the term fish is most strictly used to describe any animal with a that has throughout life and has limbs, if any, in the shape of. Many types of with common names ending in 'fish' are not fish in this; examples include,. In earlier times, even biologists did not make a distinction – sixteenth century natural historians classified also, whales, even, as well as a host of aquatic invertebrates, as fish. In fisheries, the term fish is used as a collective term, and includes, and any which is harvested.
The strict biological definition of a fish, above, is sometimes called a true fish. True fish are also referred to as finfish or fin fish to distinguish them from other aquatic life harvested in fisheries or aquaculture.Shoal or school. These are because their swimming is synchronised.A random assemblage of fish merely using some localised resource such as food or nesting sites is known simply as an aggregation.
When fish come together in an interactive, social grouping, then they may be forming either a shoal or a school depending on the degree of organisation. A shoal is a loosely organised group where each fish swims and forages independently but is attracted to other members of the group and adjusts its behaviour, such as swimming speed, so that it remains close to the other members of the group. Schools of fish are much more tightly organised, synchronising their swimming so that all fish move at the same speed and in the same direction. Shoaling and schooling behaviour is believed to provide a variety of advantages.Examples:.
Cichlids congregating at sites form an aggregation. Many minnows and characins form shoals. Anchovies, herrings and silversides are classic examples of schooling fish.While the words 'school' and 'shoal' have different meanings within biology, the distinctions are often ignored by non-specialists who treat the words as. Thus speakers of commonly use 'shoal' to describe any grouping of fish, and speakers of commonly use 'school' just as loosely. Eschmeyer, William N.; Fong, Jon David (2013). California Academy of Sciences.
Helfman, G.; Collette, B.; Facey, D. The Diversity of Fishes (1st ed.). Wiley-Blackwell.
Moyle, Peter B.; Cech, Joseph J. Fishes, An Introduction to Ichthyology (5th ed.). Benjamin Cummings. (2006). (PDF) (4th ed.). John Wiley & Sons.
Archived from (PDF) on 5 March 2013. Retrieved 30 April 2013.Further reading. Helfman, G.; Collette, B.; Facey, D.; Bowen, B. Wiley-Blackwell.
Moyle, Peter B. (1993) University of California Press. – good lay text. (2018) Eye of the shoal: A Fishwatcher's Guide to Life, the Ocean and Everything.