Most bony fish eggs are referred to as telolecithal which means that most of the egg cell cytoplasm is yolk. The yolky end of the egg (the vegetal pole) remains homogenous while the other end (the animal pole) undergoes cell division. Cleavage, or initial cell division, can only occur in a region called the blastodisc, a yolk free region located at the animal pole of the egg. The fish zygote is meroblastic, meaning the early cell divisions are not complete. This type of meroblastic cleavage is called discoidal because only the blastodisc becomes the embryo. In fish, waves of calcium released direct the process of cell division by coordinating the mitotic apparatus with the actin cytoskeleton, propagating cell division along the surface, assists in deepening the cleavage furrow, and finally heals the membrane after separation of blastomeres.
The fate of the first cells, called blastomeres, is determined by its location. This contrasts with the situation in some other animals, such as mammals, in which each blastomere can develop into any part of the organism. Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. Once zygotic gene transcription starts, slow cell division begins and cell movements are observable. During this time three cell populations become distinguished. The first population is the yolk syncytial layer. This layer forms when the cells at the vegetal pole of the blastoderm combine with the yolk cell underneath it. Later in development the yolk syncytial layer will be important in directing cell movements of gastrulation. The second cell population is the enveloping layer which is made of superficial cells from the blastoderm that eventually form a single epithetial cell layer. This layer functions in protection by allowing the embryo to develop in a hypotonic solution so the cell will not burst. Finally, the third set of blastomeres are the deep cells. These deep cells are located between the enveloping layer and the yolk syncytial layer and eventually give ride to the embryo proper.
Once blastoderm cells have covered almost half of the yolk cell, thickening throughout the margin of deep cells occurs. The thickening is referred to as the germ ring and is made up of a superficial layer, the epiblast which will become ectoderm, and an inner layer called the hypoblast which will become endoderm and mesoderm. As the blastoderm cells undergo epiboly around the yolk the internalization of cells at the blastoderm margin start to form hypoblast. Presumpive ectoderm or epiblast cells do not interalize but the deep cells (inner layer of cells) do and they become the mesoderm and endoderm. As the hypoblast cells move inward future mesoderm (hypoblast cells) start to move vegetally and proliferate but later in development these cells alter their direction and start moving towards the animal pole. However, endodermal precursors seem to lack a pattern and move randomly over the yolk.
Once the egg has become mulitcellular and positioned its germ layers with ectoderm on the outside,mesoderm in the middle, and endoderm on the inside body axes have to be determined for proper development. A dorsal- ventral axis has to form and major proteins involved are BMP and Wnt's. Both proteins are made in the ventral and lateral portions of the developing embryo. BMP2B induces cells to have ventral and lateral fates while factors such as chordin can block BMP's to dorsalize the tissue. Wnt8 induces ventral, lateral, and posterior regions of embryonic tissue. Wnt also has inhibitors like noggin to allow for the formation of dorsal tissue. In order to aid in proper development fish have an organizer center called the Nieuwkoop center. Anterior and posterior axis formation seems to be the result of interplay of FGF's, Wnt, and retinoic acid. FGF's, retinoic acid, and Wnts are required to turn on posterior genes.
Neurulation, the formation of the central nervous system, is different in fishes than in most other chordates.Convergence and extension in the epiblast recruits presumptive neural cells from the epiblast towards the midline where they form a neural keel. A neural keel is a band of neural precursors that develops a slit like lumen to eventually become the neural tube. The neural tube begins as a solid cord formed from the ectoderm. This cord then sinks into the embryo and becomes hollow, forming the neural tube. This process contrasts with the process in other chordates, which occurs by an infolding of the ectoderm to form a hollow tube.
Throughout the years advances in research have shown that neural formation relies on interactions between extrinsic signaling factors and intrinsic transcription factors. Extrinsic signals involved are BMP, Wnt, and FGF and intrinsic transcription factors like SoxB1 related genes. Secreted proteins such as BMP and its antagonist Noggin and chordin act permissively to establish the fate of neural tissue in the dorsal ectoderm and enables the formation of the neural plate.
Sex determination is variable in fish from environmental factors like temperature to genetic mechanisms. Some fish have XX/XY chromosomes and others have ZZ/ZW. So far one gene in specific, DMRT1bY, has been described as a sex determining gene. This gene is expressed before gonads develop and differentiate. Mutations in this gene lead to sex reversal from male to female. While this gene plays a major role in sex determination in some fish species other species have variations of this gene as well as some versions of the Sox gene as seen in zebrafish. Many species of fishes are hermaphrodites. Some, such as the painted comber (Serranus scriba), are synchronous hermpahrodites. These fish have both ovaries and testes and can produce both eggs and sperm at the same time. Others are sequential hermaphrodites. These fishes start life as one sex and undergo a genetically programmed sex change at some point during development. Their gonads have both ovarian and testicular tissues, with one type of tissue predominant while the fish belongs to the corresponding gender.
Coarse fishing is a term used in the United Kingdom and Ireland for angling for coarse fish. Coarse fish are freshwater fish that are distinguished from game fish. Freshwater game fish are all salmonids—most particularly salmon, trout and char—so generally coarse fish are freshwater fish that are not salmonids. There is disagreement over whether grayling should be classified as a game fish or a coarse fish.Fly fishing is the technique usually used for freshwater game fishing, while other angling techniques are usually used for coarse fishing. The sport of coarse fishing and the techniques it uses are particularly popular in the United Kingdom and mainland Europe, and as well as in some former British Commonwealth countries and among British expatriates.
The distinction between coarse fish and game fish has no taxonomic basis. It originated in the United Kingdom in the early 19th century. Prior to that time, recreational fishing was a sport of the gentry, who angled for salmon and trout and called them game fish. There was a view that other fish did not make as good eating, and they were disdained as coarse fish. Coarse fish have scales that are generally larger than the scales of game fish, and they tend to inhabit warmer and stiller waters.Demersal fish
Demersal fish live and feed on or near the bottom of seas or lakes (the demersal zone). They occupy the sea floors and lake beds, which usually consist of mud, sand, gravel or rocks. In coastal waters they are found on or near the continental shelf, and in deep waters they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters, such as abyssal depths or on the abyssal plain, but they can be found around seamounts and islands. The word demersal comes from the Latin demergere, which means to sink.
Demersal fish are bottom feeders. They can be contrasted with pelagic fish which live and feed away from the bottom in the open water column.
Demersal fish fillets contain little fish oil (one to four percent), whereas pelagic fish can contain up to 30 percent.Developmental biology
Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem cells in the adult organism.
In the late 20th century, the discipline largely transformed into evolutionary developmental biology.Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly (Poecilia sphenops) which can live in fresh water, brackish water, or salt water. The green crab (Carcinus maenas) is an example of a euryhaline invertebrate that can live in salt and brackish water. Euryhaline organisms are commonly found in habitats such as estuaries and tide pools where the salinity changes regularly. However, some organisms are euryhaline because their life cycle involves migration between freshwater and marine environments, as is the case with salmon and eels.
The opposite of euryhaline organisms are stenohaline ones, which can only survive within a narrow range of salinities. Most freshwater organisms are stenohaline, and will die in seawater, and similarly most marine organisms are stenohaline, and cannot live in fresh water.Fear of fish
Fear of fish or ichthyophobia ranges from cultural phenomena such as fear of eating fish, fear of touching raw fish, or fear of dead fish, up to irrational fear (specific phobia). Galeophobia is the fear specifically of sharks.Fish
Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods (i.e., the amphibians, reptiles, birds and mammals 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 systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces (also ichthyes) is considered a typological, but not a phylogenetic classification.
The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods.
Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature.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., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish), 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 as food. Commercial and subsistence fishers hunt fish in wild fisheries (see fishing) or farm them in ponds or in cages in the ocean (see aquaculture). They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies.Fish anatomy
Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, which is the study of how the component parts of fish function together in the living fish. In practice, fish anatomy and fish physiology complement each other, the former dealing with the structure of a fish, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in living fish.
The anatomy of fish is often shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does. The body of a fish is divided into a head, trunk and tail, although the divisions between the three are not always externally visible. The skeleton, which forms the support structure inside the fish, is either made of cartilage, in cartilaginous fish, or bone in bony fish. The main skeletal element is the vertebral column, composed of articulating vertebrae which are lightweight yet strong. The ribs attach to the spine and there are no limbs or limb girdles. The main external features of the fish, the fins, are composed of either bony or soft spines called rays which, with the exception of the caudal fins, have no direct connection with the spine. They are supported by the muscles which compose the main part of the trunk. The heart has two chambers and pumps the blood through the respiratory surfaces of the gills and on round the body in a single circulatory loop. The eyes are adapted for seeing underwater and have only local vision. There is an inner ear but no external or middle ear. Low frequency vibrations are detected by the lateral line system of sense organs that run along the length of the sides of fish, and these respond to nearby movements and to changes in water pressure.Sharks and rays are basal fish with numerous primitive anatomical features similar to those of ancient fish, including skeletons composed of cartilage. Their bodies tend to be dorso-ventrally flattened, they usually have five pairs of gill slits and a large mouth set on the underside of the head. The dermis is covered with separate dermal placoid scales. They have a cloaca into which the urinary and genital passages open, but not a swim bladder. Cartilaginous fish produce a small number of large, yolky eggs. Some species are ovoviviparous and the young develop internally but others are oviparous and the larvae develop externally in egg cases.The bony fish lineage shows more derived anatomical traits, often with major evolutionary changes from the features of ancient fish. They have a bony skeleton, are generally laterally flattened, have five pairs of gills protected by an operculum, and a mouth at or near the tip of the snout. The dermis is covered with overlapping scales. Bony fish have a swim bladder which helps them maintain a constant depth in the water column, but not a cloaca. They mostly spawn a large number of small eggs with little yolk which they broadcast into the water column.Fish disease and parasites
Like humans and other animals, fish suffer from diseases and parasites. Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth. If pathogens breach these defences, fish can develop inflammatory responses that increase the flow of blood to infected areas and deliver white blood cells that attempt to destroy the pathogens.
Specific defences are specialised responses to particular pathogens recognised by the fish's body, that is adaptative immune responses. In recent years, vaccines have become widely used in aquaculture and ornamental fish, for example vaccines for furunculosis in farmed salmon and koi herpes virus in koi.Some commercially important fish diseases are VHS, ich and whirling disease.Freshwater fish
Freshwater fish are those that spend some or all of their lives in fresh water, such as rivers and lakes, with a salinity of less than 0.05%. These environments differ from marine conditions in many ways, the most obvious being the difference in levels of salinity. To survive fresh water, the fish need a range of physiological adaptations.
41.24% of all known species of fish are found in fresh water. This is primarily due to the rapid speciation that the scattered habitats make possible. When dealing with ponds and lakes, one might use the same basic models of speciation as when studying island biogeography.Genetically modified fish
Genetically modified fish (GM fish) are organisms from the taxonomic clade which includes the classes Agnatha (jawless fish), Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish) whose genetic material (DNA) has been altered using genetic engineering techniques. In most cases, the aim is to introduce a new trait to the fish which does not occur naturally in the species, i.e. transgenesis.
GM fish are used in scientific research and kept as pets. They are being developed as environmental pollutant sentinels and for use in aquaculture food production. In 2015, the AquAdvantage salmon was approved by the US Food and Drug Administration (FDA) for commercial production, sale and consumption, making it the first genetically modified animal to be approved for human consumption. Some GM fish that have been created have promoters driving an over-production of "all fish" growth hormone. This results in dramatic growth enhancement in several species, including salmonids, carps and tilapias.Critics have objected to GM fish on several grounds, including ecological concerns, animal welfare concerns and with respect to whether using them as food is safe and whether GM fish are needed to help address the world's food needs.Hallucinogenic fish
Several species of fish are claimed to produce hallucinogenic effects when consumed. For example, Sarpa salpa, a species of sea bream, is commonly claimed to be hallucinogenic. These widely distributed coastal fish are normally found in the Mediterranean and around Spain, and along the west and south coasts of Africa. Occasionally they are found in British waters. They may induce hallucinogenic effects that are purportedly LSD-like if eaten. In 2006, two men who apparently ate the fish experienced hallucinations lasting for several days. The likelihood of hallucinations depends on the season. Sarpa salpa is known as "the fish that makes dreams" in Arabic.Other species claimed to be capable of producing hallucinations include several species of sea chub from the genus Kyphosus. It is unclear whether the toxins are produced by the fish themselves or by marine algae in their diet. Other hallucinogenic fish are Siganus spinus, called "the fish that inebriates" in Reunion Island, and Mulloidichthys flavolineatus (formerly Mulloidichthys samoensis), called "the chief of ghosts" in Hawaii.Juvenile fish
Juvenile fish go through various stages between birth and adulthood. They start as eggs which hatch into larvae. The larvae are not able to feed themselves, and carry a yolk-sac which provides their nutrition. Before the yolk-sac completely disappears, the tiny fish must become capable of feeding themselves. When they have developed to the point where they are capable of feeding themselves, the fish are called fry. When, in addition, they have developed scales and working fins, the transition to a juvenile fish is complete and it is called a fingerling. Fingerlings are typically about the size of fingers. The juvenile stage lasts until the fish is fully grown, sexually mature and interacting with other adult fish.Nangbeto Dam
The Nangbeto Dam is an embankment dam on the Mono River in the Plateaux Region of Togo. It was constructed between 1984 and 1987 for the purpose of providing hydroelectric power to both Togo and Benin as well as creating fisheries and supplying water for irrigation. The dam's 65.6 megawatts (88,000 hp) power station was commissioned in June 1987. The project was financed by the World Bank and African Development Bank at a cost of US$98.22 million.The objectives of the dam were to satisfy the medium-term requirements of Benin and Togo for power, and to provide a large water reserve, amounting to 1.7 billion cubic metres. It was expected that 1000 to 1500 tonnes of fish would be produced each year and that 43,000 hectares of land would be irrigated. Evaluation of the project six years later showed that the project had been completed on time and on budget to a satisfactory standard. The project was a good example of cooperation between the two countries. The power generation objective was satisfied but the fish development scheme had failed and the irrigation project was proceeding at a slower rate than expected. However, initial results of the cultivation of rice on the irrigated land were encouraging.The Nangbeto Dam serves part of Togo's needs for electricity and is subject to interruptions in supply when the water level is low, which may happen for periods of several months. As a result, a further dam on the Mono River further downstream at Adjaralla is being constructed, starting in 2016. The fish production scheme involved in this project and other environmental issues are being planned at an earlier stage in its development.Neurulation
Neurulation refers to the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube. The embryo at this stage is termed the neurula.
The process begins when the notochord induces the formation of the central nervous system (CNS) by signaling the ectoderm germ layer above it to form the thick and flat neural plate. The neural plate folds in upon itself to form the neural tube, which will later differentiate into the spinal cord and the brain, eventually forming the central nervous system.Different portions of the neural tube form by two different processes, called primary and secondary neurulation, in different species.
In primary neurulation, the neural plate creases inward until the edges come in contact and fuse.
In secondary neurulation, the tube forms by hollowing out of the interior of a solid precursor.Otolith
An otolith (Greek: ὠτο-, ōto- ear + λῐ́θος, líthos, a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The saccule and utricle, in turn, together make the otolith organs. These organs are what allows an organism, including humans, to perceive linear acceleration, both horizontally and vertically (gravity). They have been identified in both extinct and extant vertebrates.Counting the annual growth rings on the otoliths is a common technique in estimating the age of fish.Outline of fish
The following outline is provided as an overview of and topical guide to fish:
Fish – any member of a paraphyletic group of organisms that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., gulpers and anglerfish). At 32,000 species, fish exhibit greater species diversity than any other group of vertebrates.Papineau-Labelle Wildlife Reserve
Papineau-Labelle Wildlife Reserve is a reserve in the Laurentian Mountains of Quebec, Canada, stretching across the Laurentides and Outaouais regions.
The area was extensively logged in the late 19th to the mid-20th century. Although logging still continues on a smaller scale, the reserve was created in 1971 to provide outdoor recreation opportunities while favouring wildlife conservation. In harmony with its mandate to ensure the sustainability of resources and to foster the rational use of its territory, the reserve pursues wildlife and fish development activities by setting up spawning grounds, tree groves, interpretation trails, and nesting boxes.It is named after two historical figures of Quebec: Louis-Joseph Papineau (1786–1871), famous orator and leader of the Patriots of 1837, and Antoine Labelle (1833–1891), pastor of St. Jerome and ardent proponent of the colonization of the Upper Laurentians.The Montreal Gazette of November 18, 2008, called the Papineau-Labelle Reserve "magnificent" and included it in the 10 hot spots of Quebec's wilderness that "you should experience before you die".Stormwater
Stormwater, also spelled storm water, is water that originates during precipitation events and snow/ice melt. Stormwater can soak into the soil (infiltrate), be held on the surface and evaporate, or runoff and end up in nearby streams, rivers, or other water bodies (surface water).
In natural landscapes such as forests, the soil absorbs much of the stormwater and plants help hold stormwater close to where it falls. In developed environments, unmanaged stormwater can create two major issues: one related to the volume and timing of runoff water (flooding) and the other related to potential contaminants that the water is carrying (water pollution).
Stormwater is also an important resource as the world's human population demand exceeds the availability of readily available water. Techniques of stormwater harvesting with point source water management and purification can potentially make urban environments self-sustaining in terms of water.Strawberry Reservoir
Strawberry Reservoir is a large reservoir in the U.S. state of Utah. It is Utah's most popular fishery, receiving over 1.5 million angling hours annually and is part of the Blue Ribbon Fisheries program. Game fish in the reservoir include sterilized rainbow trout, bear lake cutthroat trout, kokanee salmon and crayfish. It is located 23 miles (37 km) southeast of Heber, Utah on U.S. Route 40.
The reservoir is situated in Strawberry Valley. This valley is normally part of the Colorado River drainage. The dam was constructed to divert water into Utah Valley.
Strawberry Reservoir was the 2006 recipient of the American Fisheries Society's outstanding sport fish development/restoration Project of the Year award.