Herring are various species of forage fish , mostly belonging to the family of Clupeidae .
115-566: Herring often move in large schools around fishing banks and near the coast, found particularly in shallow, temperate waters of the North Pacific and North Atlantic Oceans , including the Baltic Sea , as well as off the west coast of South America. Three species of Clupea (the type genus of the herring family Clupeidae) are recognised, and comprise about 90% of all herrings captured in fisheries. The most abundant of these species
230-554: A staple food source since at least 3000 BC. The fish is served numerous ways, and many regional recipes are used: eaten raw, fermented, pickled , or cured by other techniques, such as being smoked as kippers . Herring are very high in the long-chain omega-3 fatty acids EPA and DHA . They are a source of vitamin D . Water pollution influences the amount of herring that may be safely consumed. For example, large Baltic herring slightly exceeds recommended limits with respect to PCB and dioxin , although some sources point out that
345-441: A "rebound" effect following overuse of decongestants may produce nasal or sinus drainage problems and circumstances that promote infection. During cold, dry seasons, the mucus lining nasal passages tends to dry out, meaning that mucous membranes must work harder, producing more mucus to keep the cavity lined. As a result, the nasal cavity can fill up with mucus. At the same time, when air is exhaled, water vapor in breath condenses as
460-487: A calming one and a powerful social motivation for remaining in an aggregation. Herring, for instance, will become very agitated if they are isolated from conspecifics. Because of their adaptation to schooling behaviour they are rarely displayed in aquaria . Even with the best facilities aquaria can offer they become fragile and sluggish compared to their quivering energy in wild schools. It has also been proposed that swimming in groups enhances foraging success. This ability
575-443: A chance to escape or to never join a shoal with larger fish. It has been shown that small fish avoid joining a group with larger fish, although big fish do not avoid joining small conspecifics. This sorting mechanism based on increased quality of perception could have resulted in homogeneity of size of fish in shoals, which would increase the capacity for moving in synchrony. Predators have devised various countermeasures to undermine
690-420: A charge selective diffusion barrier, thus significantly affecting the transportation of agents. Among particles with various surface zeta potentials , cationic particles tend to have a low depth of penetration, neutral ones possess medium penetration, and anionic ones have the largest penetration depth. Furthermore, the effect of charge selectivity changes when the status of the mucus varies, i.e., native mucus has
805-535: A disciplined and coordinated school, then shift back to an amorphous shoal within seconds. Such shifts are triggered by changes of activity from feeding, resting, travelling or avoiding predators. When schooling fish stop to feed, they break ranks and become shoals. Shoals are more vulnerable to predator attack. The shape a shoal or school takes depends on the type of fish and what the fish are doing. Schools that are travelling can form long thin lines, or squares or ovals or amoeboid shapes. Fast moving schools usually form
920-623: A feeding ground for larger predator fish. Most upwellings are coastal, and many of them support some of the most productive fisheries in the world. Regions of notable upwelling include coastal Peru , Chile , Arabian Sea , western South Africa , eastern New Zealand and the California coast. Copepods , the primary zooplankton , are a major item on the forage fish menu. They are a group of small crustaceans found in ocean and freshwater habitats . Copepods are typically one millimetre (0.04 in) to two millimetres (0.08 in) long, with
1035-407: A feeding method also used by adult herring on larger prey items like krill. If prey concentrations reach very high levels, as in microlayers, at fronts, or directly below the surface, herring become filter feeders , driving several meters forward with wide open mouth and far expanded opercula , then closing and cleaning the gill rakers for a few milliseconds. Copepods, the primary zooplankton, are
1150-405: A few centimetres. If copepod concentrations reach high levels, schooling herrings adopt a method called ram feeding . In the photo below, herring ram feed on a school of copepods. They swim with their mouths wide open and their operculae fully expanded. The fish swim in a grid where the distance between them is the same as the jump length of their prey, as indicated in the animation above right. In
1265-912: A forage fish of the smelt family found in the Atlantic and Arctic oceans. In summer, they graze on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat krill and other crustaceans . The capelin move inshore in large schools to spawn and migrate in spring and summer to feed in plankton rich areas between Iceland , Greenland , and Jan Mayen . The migration is affected by ocean currents . Around Iceland maturing capelin make large northward feeding migrations in spring and summer. The return migration takes place in September to November. The spawning migration starts north of Iceland in December or January. This theory states that groups of fish may save energy when swimming together, much in
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#17327658163171380-450: A herring in one locality might be called something else in another locality. Some examples: The species of Clupea belong to the larger family Clupeidae (herrings, shads , sardines , menhadens ), which comprises some 200 species that share similar features. These silvery-coloured fish have a single dorsal fin , which is soft, without spines. They have no lateral line and have a protruding lower jaw. Their size varies between subspecies:
1495-430: A herring to eventually snap the copepod. A single juvenile herring could never catch a large copepod. A third proposed benefit of fish groups is that they serve a reproductive function. They provide increased access to potential mates, since finding a mate in a shoal does not take much energy. And for migrating fish that navigate long distances to spawn, it is likely that the navigation of the shoal, with an input from all
1610-409: A hydrodynamic advantage, the leader will be the first to the food. More recent work suggests that, after individuals at the front of the school encounter and ingest more food, they then relocate further back within the school due to the locomotor constraints generated during meal digestion. It is commonly observed that schooling fish are particularly in danger of being eaten if they are separated from
1725-451: A loose way, with each fish swimming and foraging somewhat independently, they are nonetheless aware of the other members of the group as shown by the way they adjust behaviour such as swimming, so as to remain close to the other fish in the group. Shoaling groups can include fish of disparate sizes and can include mixed-species subgroups. If the shoal becomes more tightly organised, with the fish synchronising their swimming so they all move at
1840-436: A major item on the forage fish menu. Copepods are typically 1–2 mm ( 1 ⁄ 32 – 3 ⁄ 32 in) long, with a teardrop-shaped body. Some scientists say they form the largest animal biomass on the planet. Copepods are very alert and evasive. They have large antennae (see photo below left). When they spread their antennae, they can sense the pressure wave from an approaching fish and jump with great speed over
1955-430: A negative side chain when the pH value is above 3.9, while a neutrally charged side chain will be introduced as pH value drops below 3.9. Thus, the number of negative charges in mucus is influenced by the pH value of surrounding environment. That is, the polyelectrolyte effect of mucus is largely affected by the pH value of solution due to the charge variation of acidic amino acid residues on the mucin backbone. For instance,
2070-461: A part but supporting evidence has not been found so far. The lateral line is a line running along each side of the fish from the gill covers to the base of the tail. In laboratory experiments the lateral lines of schooling fish have been removed. They swam closer, leading to a theory that the lateral lines provide additional stimuli input when the fish get too close. The lateral-line system is very sensitive to changes in water currents and vibration in
2185-409: A school of herring into a tight bait ball . Different predatory species then use different techniques to pick the fish off in the bait ball. The sailfish raises its sail to make it appear much larger. Swordfish charge at high speed through the bait balls, slashing with their swords to kill or stun prey. They then turn and return to consume their "catch". Thresher sharks use their long tails to stun
2300-683: A short life-cycle, living only two or three years. Adult sardines, about two years old, mass on the Agulhas Bank where they spawn during spring and summer, releasing tens of thousands of eggs into the water. The adult sardines then make their way in hundreds of shoals towards the sub-tropical waters of the Indian Ocean . A larger shoal might be 7 kilometres (4.3 mi) long, 1.5 kilometres (0.93 mi) wide and 30 metres (98 ft) deep. Huge numbers of sharks, dolphins, tuna, sailfish, Cape fur seals and even killer whales congregate and follow
2415-413: A single school. These schools move along coastlines and traverse the open oceans. Herring schools in general have very precise arrangements which allow the school to maintain relatively constant cruising speeds. Herrings have excellent hearing, and their schools react very rapidly to a predator. The herrings keep a certain distance from a moving scuba diver or a cruising predator like a killer whale, forming
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#17327658163172530-430: A teardrop shaped body. Some scientists say they form the largest animal biomass on the planet. Copepods are very alert and evasive. They have large antennae (see photo below left). When they spread their antennae they can sense the pressure wave from an approaching fish and jump with great speed over a few centimeters. If copepod concentrations reach high levels, schooling herrings adopt a method called ram feeding . In
2645-422: A threefold higher potential to limit agent penetration than purified mucus. Mucus is also produced by a number of other animals. All fish are covered in mucus secreted from glands all over their bodies. Invertebrates such as snails and slugs secrete mucus called snail slime to enable movement, and to prevent their bodies from drying out. Their reproductive systems also make use of mucus for example in
2760-418: A vacuole which looks like a doughnut from a spotter plane. Many species of large predatory fish also school, including many highly migratory fish , such as tuna and some oceangoing sharks . Cetaceans such as dolphins, porpoises and whales, operate in organised social groups called pods . "Shoaling behaviour is generally described as a trade-off between the anti-predator benefits of living in groups and
2875-636: A wedge shape, while shoals that are feeding tend to become circular. Forage fish are small fish which are preyed on by larger predators for food. Predators include other larger fish, seabirds and marine mammals . Typical ocean forage fish are small, filter-feeding fish such as herring , anchovies and menhaden . Forage fish compensate for their small size by forming schools. Some swim in synchronised grids with their mouths open so they can efficiently filter feed on plankton . These schools can become huge, moving along coastlines and migrating across open oceans. The shoals are concentrated food resources for
2990-423: A woman's fertile time at the mid-point of the cycle. Awareness of the woman's fertile time allows a couple to time intercourse to improve the odds of pregnancy. It is also proposed as a method to avoid pregnancy. In general, nasal mucus is clear and thin, serving to filter air during inhalation. During times of infection, mucus can change color to yellow or green either as a result of trapped bacteria or due to
3105-428: Is a polymeric protein secreted from submucosal glands and some goblet cells, and this is in the form of strands. In the airways—the trachea , bronchi , and bronchioles —the lining of mucus is produced by specialized airway epithelial cells called goblet cells , and submucosal glands . Small particles such as dust, particulate pollutants , and allergens , as well as infectious agents and bacteria are caught in
3220-418: Is a viscous colloid containing inorganic salts , antimicrobial enzymes (such as lysozymes ), immunoglobulins (especially IgA ), and glycoproteins such as lactoferrin and mucins , which are produced by goblet cells in the mucous membranes and submucosal glands . Mucus serves to protect epithelial cells in the linings of the respiratory , digestive , and urogenital systems , and structures in
3335-423: Is also produced by some microorganisms . In the human respiratory system , mucus is part of the airway surface liquid (ASL), also known as epithelial lining fluid (ELF), that lines most of the respiratory tract . The airway surface liquid consists of a sol layer termed the periciliary liquid layer and an overlying gel layer termed the mucus layer. The periciliary liquid layer is so named as it surrounds
3450-443: Is an elaboration of safety in numbers , and interacts with the confusion effect. A given predator attack will eat a smaller proportion of a large shoal than a small shoal. Hamilton proposed that animals aggregate because of a "selfish" avoidance of a predator and was thus a form of cover-seeking. Another formulation of the theory was given by Turner and Pitcher and was viewed as a combination of detection and attack probabilities. In
3565-412: Is controversial. Fish can be obligate or facultative (optional) shoalers. Obligate shoalers, such as tunas , herrings and anchovy , spend all of their time shoaling or schooling, and become agitated if separated from the group. Facultative shoalers, such as Atlantic cod , saiths and some carangids , shoal only some of the time, perhaps for reproductive purposes. Shoaling fish can shift into
Herring - Misplaced Pages Continue
3680-510: Is essential in the final stages of a predator attack. Electro-receptive animals may localize a field source by using spatial non-uniformities. To produce separate signals, individual prey must be about five body widths apart. If objects are too close together to be distinguished, they will form a blurred image. Based on this it was suggested that schooling may confuse the ESS of predators. A third potential anti-predator effect of animal aggregations
3795-442: Is generally symptom-based; often it is sufficient to allow the immune system to fight off the virus over time. Obstructive lung diseases often result from impaired mucociliary clearance that can be associated with mucus hypersecretion, and these are sometimes referred to as mucoobstructive lung diseases . Techniques of airway clearance therapy can help to clear secretions, maintain respiratory health, and prevent inflammation in
3910-663: Is important to schooling. The importance of vision is also indicated by the behaviour of fish who have been temporarily blinded. Schooling species have eyes on the sides of their heads, which means they can easily see their neighbours. Also, schooling species often have "schooling marks" on their shoulders or the base of their tails, or visually prominent stripes, which provide reference marks when schooling, similar in function to passive markers in artificial motion capture. However fish without these markers will still engage in schooling behaviour, though perhaps not as efficiently. Other senses are also used. Pheromones or sound may also play
4025-403: Is known as mucus hypersecretion . Chronic mucus hypersecretion results in the chronic productive cough of chronic bronchitis , and is generally synonymous with this. Excessive mucus can narrow the airways, limit airflow, and accelerate a decline in lung function. In the human digestive system , mucus is used as a lubricant for materials that must pass over membranes, e.g., food passing down
4140-653: Is seen in the structure of schools of predatory fish. Partridge and others analysed the school structure of Atlantic bluefin tuna from aerial photographs and found that the school assumed a parabolic shape, a fact that was suggestive of cooperative hunting in this species. "The reason for this is the presence of many eyes searching for the food. Fish in shoals "share" information by monitoring each other's behaviour closely. Feeding behaviour in one fish quickly stimulates food-searching behaviour in others. Fertile feeding grounds for forage fish are provided by ocean upwellings. Oceanic gyres are large-scale ocean currents caused by
4255-635: Is the Atlantic herring , which comprises over half of all herring capture. Fish called herring are also found in the Arabian Sea , Indian Ocean , and Bay of Bengal . Herring played an important role in the history of marine fisheries in Europe, and early in the 20th century, their study was fundamental to the development of fisheries science . These oily fish also have a long history as an important food fish , and are often salted , smoked , or pickled . Herring were also known as "silver darlings" in
4370-449: Is the "many eyes" hypothesis. This theory states that as the size of the group increases, the task of scanning the environment for predators can be spread out over many individuals. Not only does this mass collaboration presumably provide a higher level of vigilance, it could also allow more time for individual feeding. A fourth hypothesis for an anti-predatory effect of fish schools is the "encounter dilution" effect. The dilution effect
4485-458: Is the fundamental characteristic of cystic fibrosis , an inherited disease caused by mutations in the CFTR gene, which encodes a chloride channel . This defect leads to the altered electrolyte composition of mucus, which triggers its hyperabsorption and dehydration. Such low-volume, viscous, acidic mucus has a reduced antimicrobial function, which facilitates bacterial colonisation. The thinning of
4600-471: Is the general term for any collection of fish that have gathered together in some locality. Fish aggregations can be structured or unstructured. An unstructured aggregation might be a group of mixed species and sizes that have gathered randomly near some local resource, such as food or nesting sites. If, in addition, the aggregation comes together in an interactive, social way, they may be said to be shoaling . Although shoaling fish can relate to each other in
4715-561: Is then known as phlegm which may be coughed up as sputum to clear the airway. Increased mucus production in the upper respiratory tract is a symptom of many common ailments, such as the common cold , and influenza . Nasal mucus may be removed by blowing the nose or by using nasal irrigation . Excess nasal mucus, as with a cold or allergies , due to vascular engorgement associated with vasodilation and increased capillary permeability caused by histamines , may be treated cautiously with decongestant medications. Thickening of mucus as
Herring - Misplaced Pages Continue
4830-715: The Atlantic herring (the type species) found in the North Atlantic, and the Pacific herring mainly found in the North Pacific. Subspecific divisions have been suggested for both the Atlantic and Pacific herrings, but their biological basis remains unclear. In addition, a number of related species, all in the Clupeidae, are commonly referred to as herrings. The table immediately below includes those members of
4945-686: The Baltic herring ( Clupea harengus membras ) is small, 14 to 18 cm (about 5.5 to 7 inches); the proper Atlantic herring ( Clupea harengus harengus ) can grow to about 46 cm (18 in) and weigh up 700 g (1.5 lb); and Pacific herring grow to about 38 cm (15 in). At least one stock of Atlantic herring spawns in every month of the year. Each spawns at a different time and place (spring, summer, autumn, and winter herrings). Greenland populations spawn in 0–5 metres (0–16 feet) of water, while North Sea (bank) herrings spawn at down to 200 m (660 ft) in autumn. Eggs are laid on
5060-469: The Coriolis effect . Wind-driven surface currents interact with these gyres and the underwater topography, such as seamounts , fishing banks , and the edge of continental shelves , to produce downwellings and upwellings . These can transport nutrients which plankton thrive on. The result can be rich feeding grounds attractive to the plankton feeding forage fish. In turn, the forage fish themselves become
5175-467: The blue whale , is said to be the largest biomechanical event on Earth. Adult herring are harvested for their flesh and eggs, and they are often used as baitfish . The trade in herring is an important sector of many economies around the world. In Europe, the fish has been called the "silver of the sea", and its trade has been so significant to many countries that it has been regarded as the most commercially important fishery in history. Herring has been
5290-413: The cilia and lies on top of the surface epithelium. The periciliary liquid layer surrounding the cilia consists of a gel meshwork of cell-tethered mucins and polysaccharides. The mucus blanket aids in the protection of the lungs by trapping foreign particles before they can enter them, in particular through the nose during normal breathing. Mucus is made up of a fluid component of around 95% water,
5405-414: The esophagus . Mucus is extremely important in the gastrointestinal tract . It forms an essential layer in the colon and in the small intestine that helps reduce intestinal inflammation by decreasing bacterial interaction with intestinal epithelial cells. The layer of mucus of the gastric mucosa lining the stomach is vital to protect the stomach lining from the highly acidic environment within it. In
5520-411: The lateral line organ (LLO) as well as the electrosensory system (ESS) of predators. Fin movements of a single fish act as a point-shaped wave source, emitting a gradient by which predators might localize it. Since fields of many fish will overlap, schooling should obscure this gradient, perhaps mimicking pressure waves of a larger animal, and more likely confuse the lateral line perception. The LLO
5635-406: The mucin secretions from the goblet cells, and the submucosal glands (2–3% glycoproteins), proteoglycans (0.1–0.5%), lipids (0.3–0.5%), proteins, and DNA. The major mucins secreted – MUC5AC and MUC5B - are large polymers that give the mucus its rheologic or viscoelastic properties. MUC5AC is the main gel-forming mucin secreted by goblet cells, in the form of threads and thin sheets. MUC5B
5750-508: The pelagic zone . Conversely, they are a central prey item or forage fish for higher trophic levels . The reasons for this success are still enigmatic; one speculation attributes their dominance to the huge, extremely fast cruising schools they inhabit. Herring feed on phytoplankton , and as they mature, they start to consume larger organisms. They also feed on zooplankton, tiny animals found in oceanic surface waters , and small fish and fish larvae. Copepods and other tiny crustaceans are
5865-427: The visual and auditory systems from pathogenic fungi , bacteria and viruses . Most of the mucus in the body is produced in the gastrointestinal tract . Amphibians , fish , snails , slugs , and some other invertebrates also produce external mucus from their epidermis as protection against pathogens, to help in movement, and to line fish gills . Plants produce a similar substance called mucilage that
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#17327658163175980-407: The Atlantic bottlenose dolphin takes this one step further with what has become known as strand feeding, where the fish are driven onto mud banks and retrieved from there. Common bottlenose dolphins have been observed using another technique. One dolphin acts as a "driver" and herds a school of fish towards several other dolphins who form a barrier. The driver dolphin slaps its fluke which makes
6095-742: The Baltic, copepods of the genus Acartia can be present in large numbers. However, they are small in size with a high escape response, so herring and sprat avoid trying to catch them. These copepods also tend to dwell more in surface waters, whereas herring and sprat, especially during the day, tend to dwell in deeper waters. Predators of herring include seabirds , marine mammals such as dolphins , porpoises , whales , seals , and sea lions , predatory fish such as sharks , billfish , tuna , salmon , striped bass , cod , and halibut . Fishermen also catch and eat herring. The predators often cooperate in groups, using different techniques to panic or herd
6210-565: The United Kingdom. A number of different species, most belonging to the family Clupeidae , are commonly referred to as herrings. The origins of the term "herring" is somewhat unclear, though it may derive from the same source as the Old High German heri meaning a "host, multitude", in reference to the large schools they form. The type genus of the herring family Clupeidae is Clupea . Clupea contains only two species:
6325-406: The air. Some whales lunge feed on bait balls. Lunge feeding is an extreme feeding method, where the whale accelerates from below the bait ball to a high velocity and then opens its mouth to a large gape angle. This generates the water pressure required to expand its mouth and engulf and filter a huge amount of water and fish. Lunge feeding by rorquals , a family of huge baleen whales that includes
6440-435: The airways. A unique umbilical cord lining epithelial stem cell expresses MUC1 , termed (CLEC-muc). This has been shown to have good potential in the regeneration of the cornea . Mucus is able to absorb water or dehydrate through pH variations. The swelling capacity of mucus stems from the bottlebrush structure of mucin within which hydrophilic segments provide a large surface area for water absorption. Moreover,
6555-598: The almost endless stream of herring allows a herring to eventually snap up the copepod. A single juvenile herring could never catch a large copepod. Other pelagic prey eaten by herring includes fish eggs, larval snails , diatoms by herring larvae below 20 mm ( 13 ⁄ 16 in), tintinnids by larvae below 45 mm ( 1 + 3 ⁄ 4 in), molluscan larvae, menhaden larvae, krill , mysids , smaller fishes, pteropods , annelids , Calanus spp., Centropagidae , and Meganyctiphanes norvegica . Herrings, along with Atlantic cod and sprat , are
6670-477: The animation, juvenile herring hunt the copepods in this synchronised way. The copepods sense with their antennae the pressure wave of an approaching herring and react with a fast escape jump. The length of the jump is fairly constant. The fish align themselves in a grid with this characteristic jump length. A copepod can dart about 80 times before it tires. After a jump, it takes it 60 milliseconds to spread its antennae again, and this time delay becomes its undoing, as
6785-411: The body's reaction to viral infection. For example, Staphylococcus aureus infection may turn the mucus yellow. The green color of mucus comes from the heme group in the iron-containing enzyme myeloperoxidase secreted by white blood cells as a cytotoxic defense during a respiratory burst . In the case of bacterial infection, the bacterium becomes trapped in already-clogged sinuses , breeding in
6900-475: The cancer-reducing effect of omega-3 fatty acids is statistically stronger than the carcinogenic effect of PCBs and dioxins. The contaminant levels depend on the age of the fish which can be inferred from their size. Baltic herrings larger than 17 cm (6.7 in) may be eaten twice a month, while herrings smaller than 17 cm can be eaten freely. Mercury in fish also influences the amount of fish that women who are pregnant or planning to be pregnant within
7015-411: The case of a viral infection such as cold or flu , the first stage and also the last stage of the infection cause the production of a clear, thin mucus in the nose or back of the throat. As the body begins to react to the virus (generally one to three days), mucus thickens and may turn yellow or green. Viral infections cannot be treated with antibiotics, and are a major avenue for their misuse. Treatment
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#17327658163177130-707: The chance of individual capture), enhanced foraging success, and higher success in finding a mate. It is also likely that fish benefit from shoal membership through increased hydrodynamic efficiency. Fish use many traits to choose shoalmates. Generally they prefer larger shoals, shoalmates of their own species, shoalmates similar in size and appearance to themselves, healthy fish, and kin (when recognized). The oddity effect posits that any shoal member that stands out in appearance will be preferentially targeted by predators. This may explain why fish prefer to shoal with individuals that resemble themselves. The oddity effect thus tends to homogenize shoals. An aggregation of fish
7245-759: The charged groups in the polyelectrolytes attract counter-ions with opposite charges, thereby leading to a solute concentration gradient. An osmotic pressure is introduced to equalize the concentration of solute throughout the system by driving water to flow from the low concentration areas to the high concentration areas. In short, the influx and outflux of water within mucus, managed by the polyelectrolyte effect, contribute to mucus' tunable swelling capacity. The ionic charges of mucin are mainly provided by acidic amino acids including aspartic acid ( pKa =3.9) and glutamic acid (pKa=4.2). The charges of acidic amino acids will change with environmental pH value due to acid dissociation and association. Aspartic acid, for example, has
7360-464: The charged residue on mucin is protonated at a normal pH value of the stomach, approximately pH 2. In this case, there is scarcely polyelectrolyte effect, thereby causing compact mucus with little swelling capacity. However, a kind of bacteria, Helicobacter pylori , is prone to producing base to elevate the pH value in stomach, leading to the deprotonation of aspartic acids and glutamic acids, i.e., from neutral to negative-charged. The negative charges in
7475-417: The confusion of casting nets, the dolphins catch a large number of fish as well. Intraspecific cooperative foraging techniques have also been observed, and some propose that these behaviours are transmitted through cultural means. Rendell & Whitehead have proposed a structure for the study of culture in cetaceans. Some whales lunge feed on bait balls. Lunge feeding is an extreme feeding method, in which
7590-439: The costs of increased foraging competition." Landa (1998) argues that the cumulative advantages of shoaling, as elaborated below, are strong selective inducements for fish to join shoals. Parrish et al. (2002) argue similarly that schooling is a classic example of emergence , where there are properties that are possessed by the school but not by the individual fish. Emergent properties give an evolutionary advantage to members of
7705-410: The defensive shoaling and schooling manoeuvres of forage fish. The sailfish raises its sail to make it appear much larger so it can herd a school of fish or squid. Swordfish charge at high speed through forage fish schools, slashing with their swords to kill or stun prey. They then turn and return to consume their "catch". Thresher sharks use their long tails to stun shoaling fishes. Before striking,
7820-435: The detection component of the theory, it was suggested that potential prey might benefit by living together since a predator is less likely to chance upon a single group than a scattered distribution. In the attack component, it was thought that an attacking predator is less likely to eat a particular fish when a greater number of fish are present. In sum, a fish has an advantage if it is in the larger of two groups, assuming that
7935-435: The egg layers are too thick they suffer from oxygen depletion and often die, entangled in a maze of mucus . They need substantial water microturbulence, generally provided by wave action or coastal currents . Survival is highest in crevices and behind solid structures, because predators feast on openly exposed eggs. The individual eggs are 1 to 1.4 mm ( 3 ⁄ 64 to 1 ⁄ 16 in) in diameter, depending on
8050-500: The end of these spiralling runs often carries it into the air. Some predators, such as dolphins, hunt in groups of their own. One technique employed by many dolphin species is herding , where a pod will control a school of fish while individual members take turns ploughing through and feeding on the more tightly packed school (a formation commonly known as a bait ball ). Corralling is a method where fish are chased to shallow water where they are more easily captured. In South Carolina ,
8165-474: The eyes are well pigmented. The rest of the body is nearly transparent, virtually invisible under water and in natural lighting conditions. The dorsal fin forms at 15 to 17 mm ( 19 ⁄ 32 to 21 ⁄ 32 in), the anal fin at about 30 mm ( 1 + 3 ⁄ 16 in)—the ventral fins are visible and the tail becomes well forked at 30 to 35 mm ( 1 + 3 ⁄ 8 in)— at about 40 mm ( 1 + 9 ⁄ 16 in),
8280-494: The family Clupeidae referred to by FishBase as herrings which have been assessed by the International Union for Conservation of Nature . Also, a number of other species are called herrings, which may be related to clupeids or just share some characteristics of herrings (such as the lake herring , which is a salmonid ). Just which of these species are called herrings can vary with locality, so what might be called
8395-440: The fish leap into the air. As the fish leap, the driver dolphin moves with the barrier dolphins and catches the fish in the air. This type of cooperative role specialization seems to be more common in marine animals than in terrestrial animals , perhaps because the oceans have more variability in prey diversity, biomass , and predator mobility. During the sardine run , as many as 18,000 dolphins, behaving like sheepdogs, herd
8510-555: The great marine predators. These sometimes immense gatherings fuel the ocean food web . Most forage fish are pelagic fish , which means they form their schools in open water, and not on or near the bottom ( demersal fish ). Forage fish are short-lived, and go mostly unnoticed by humans. The predators are keenly focused on the shoals, acutely aware of their numbers and whereabouts, and make migrations themselves, often in schools of their own, that can span thousands of miles to connect with, or stay connected with them. Herring are among
8625-401: The group is swimming in the same direction in a coordinated manner, they are schooling . In common usage, the terms are sometimes used rather loosely. About one quarter of fish species shoal all their lives, and about one half shoal for part of their lives. Fish derive many benefits from shoaling behaviour including defence against predators (through better predator detection and by diluting
8740-495: The human female reproductive system, cervical mucus prevents infection and provides lubrication during sexual intercourse. The consistency of cervical mucus varies depending on the stage of a woman's menstrual cycle. At ovulation cervical mucus is clear, runny, and conducive to sperm ; post-ovulation, mucus becomes thicker and is more likely to block sperm. Several fertility awareness methods rely on observation of cervical mucus, as one of three primary fertility signs, to identify
8855-432: The individual animals to follow three rules: An example of such a simulation is the boids program created by Craig Reynolds in 1986. Another is the self-propelled particle model introduced by Vicsek et al. in 1995 Many current models use variations on these rules. For instance, many models implement these three rules through layered zones around each fish. The shape of these zones will necessarily be affected by
8970-458: The inhaled air and prevents tissues such as the nasal and airway epithelia from drying out. Mucus is produced continuously in the respiratory tract . Mucociliary action carries it down from the nasal passages and up from the rest of the tract to the pharynx, with most of it being swallowed subconsciously. Sometimes in times of respiratory illness or inflammation, mucus can become thickened with cell debris, bacteria, and inflammatory cells. It
9085-554: The larva begins to look like a herring. Herring larvae are very slender and can easily be distinguished from all other young fish of their range by the location of the vent, which lies close to the base of the tail; however, distinguishing clupeoids one from another in their early stages requires critical examination, especially telling herring from sprats . At one year, they are about 10 cm (4 in) long, and they first spawn at three years. Herrings consume copepods , arrow worms , pelagic amphipods , mysids , and krill in
9200-503: The larvae develop into juvenile fish. When they are old enough, they aggregate into dense shoals and migrate southwards, returning to the Agulhas banks to restart the cycle. The development of schooling behavior was probably associated with an increased quality of perception, predatory lifestyle and size sorting mechanisms to avoid cannibalism. In filter-feeding ancestors, before vision and the octavolateralis system (OLS) had developed,
9315-406: The moist, nutrient-rich environment. Sinusitis is an uncomfortable condition that may include congestion of mucus. A bacterial infection in sinusitis will cause discolored mucus and would respond to antibiotic treatment; viral infections typically resolve without treatment. Almost all sinusitis infections are viral and antibiotics are ineffective and not recommended for treating typical cases. In
9430-612: The more spectacular schooling fish. They aggregate together in huge numbers. The largest schools are often formed during migrations by merging with smaller schools. "Chains" of schools one hundred kilometres (60 miles) long have been observed of mullet migrating in the Caspian Sea . Radakov estimated herring schools in the North Atlantic can occupy up to 4.8 cubic kilometres (1.2 cubic miles) with fish densities between 0.5 and 1.0 fish/cubic metre ( 3 ⁄ 8 to 3 ⁄ 4 fish per cubic yard), totalling about three billion fish in
9545-412: The most common zooplankton eaten by herring. During daylight, herring stay in the safety of deep water, feeding at the surface only at night when the chance of being seen by predators is less. They swim along with their mouths open, filtering the plankton from the water as it passes through their gills. Young herring mostly hunt copepods individually, by means of "particulate feeding" or "raptorial feeding",
9660-630: The most important commercial species to humans in the Baltic Sea. The analysis of the stomach contents of these fish indicate Atlantic cod is the top predator, preying on the herring and sprat. Sprat are competitive with herring for the same food resources. This is evident in the two species' vertical migration in the Baltic Sea, where they compete for the limited zooplankton available and necessary for their survival. Sprat are highly selective in their diet and eat only zooplankton, while herring are more eclectic, adjusting their diet as they grow in size. In
9775-494: The mucus greatly increase, thus inducing the polyelectrolyte effect and the swelling of the mucus. This swelling effect increases the pore size of the mucus and decreases mucus' viscosity, which allows bacteria to penetrate and migrate into the mucus and cause disease. The high selective permeability of mucus plays a crucial role in the healthy state of human beings by limiting the penetration of molecules, nutrients, pathogens, and drugs. The charge distribution within mucus serves as
9890-402: The mucus layer ultimately affects the periciliary liquid layer, which becomes dehydrated, compromising ciliary function, and impairing mucociliary clearance. A respiratory therapist can recommend airway clearance therapy which uses a number of clearance techniques to help with the clearance of mucus. In the lower respiratory tract excessive mucus production in the bronchi and bronchioles
10005-411: The neighbours of a fish in a school, it is thought that efficiency gains do occur in the wild. More recent experiments with groups of fish swimming in flumes support this, with fish reducing their swimming costs by as much as 20% as compared to when the same fish are swimming in isolation. Landa (1998) argued that the leader of a school constantly changes, because while being in the body of a school gives
10120-674: The next one or two years may safely eat. The herring has played a highly significant role in history both socially and economically. During the Middle Ages, herring prompted the founding of Great Yarmouth and Copenhagen and played a critical role in the medieval development of Amsterdam . In 1274, while on his deathbed at the monastery of Fossanova (south of Rome, Italy), when encouraged to eat something to regain his strength, Thomas Aquinas asked for fresh herring. Shoaling and schooling In biology, any group of fish that stay together for social reasons are shoaling , and if
10235-403: The photo below, herring ram feed on a school of copepods . They swim with their mouth wide open and their opercula fully expanded. The fish swim in a grid where the distance between them is the same as the jump length of their prey, as indicated in the animation above right. In the animation, juvenile herring hunt the copepods in this synchronised way. The copepods sense with their antennae
10350-408: The predator's visual channel. Milinski and Heller's findings have been corroborated both in experiment and computer simulations. "Shoaling fish are the same size and silvery, so it is difficult for a visually oriented predator to pick an individual out of a mass of twisting, flashing fish and then have enough time to grab its prey before it disappears into the shoal." Schooling behaviour confuses
10465-407: The pressure-wave of an approaching herring and react with a fast escape jump. The length of the jump is fairly constant. The fish align themselves in a grid with this characteristic jump length. A copepod can dart about 80 times before it tires. After a jump, it takes it 60 milliseconds to spread its antennae again, and this time delay becomes its undoing, as the almost endless stream of herrings allows
10580-542: The probability of detection and attack does not increase disproportionately with the size of the group. Schooling forage fish are subject to constant attacks by predators. An example is the attacks that take place during the African sardine run . The African sardine run is a spectacular migration by millions of silvery sardines along the southern coastline of Africa. In terms of biomass, the sardine run could rival East Africa's great wildebeest migration . Sardines have
10695-494: The risk of predation would have been limited and mainly due to invertebrate predators. Hence, at that time, safety in numbers was probably not a major incentive for gathering in shoals or schools. The development of vision and the OLS would have permitted detection of potential prey. This could have led to an increased potential for cannibalism within the shoal. On the other hand, increased quality of perception would give small individuals
10810-406: The same speed and in the same direction, then the fish may be said to be schooling . Schooling fish are usually of the same species and the same age/size. Fish schools move with the individual members precisely spaced from each other. The schools undertake complicated manoeuvres, as though the schools have minds of their own. The intricacies of schooling are far from fully understood, especially
10925-490: The sardines into bait balls, or corral them in shallow water. Once the bait balls are rounded up, the dolphins and other predators take turns ploughing through them, gorging on the fish as they sweep through. Seabirds also attack them from above, flocks of gannets , cormorants , terns and gulls . Some of these seabirds plummet from heights of 30 metres (100 feet), plunging through the water leaving vapour-like trails, similar to that of fighter planes. Gannets plunge into
11040-450: The school which non members do not receive. Support for the social and genetic function of aggregations, especially those formed by fish, can be seen in several aspects of their behaviour. For instance, experiments have shown that individual fish removed from a school will have a higher respiratory rate than those found in the school. This effect has been attributed to stress, and the effect of being with conspecifics therefore appears to be
11155-417: The school. Several anti-predator functions of fish schools have been proposed. One potential method by which fish schools might thwart predators is the "predator confusion effect" proposed and demonstrated by Milinski and Heller (1978). This theory is based on the idea that it becomes difficult for predators to choose individual prey from groups because the many moving targets create a sensory overload of
11270-471: The sea bed, on rock, stones, gravel, sand or beds of algae . Females may deposit from 20,000 to 40,000 eggs, according to age and size, averaging about 30,000. In sexually mature herring, the genital organs grow before spawning, reaching about one-fifth of its total weight. The eggs sink to the bottom, where they stick in layers or clumps to gravel, seaweed, or stones, by means of their mucous coating, or to any other objects on which they chance to settle. If
11385-531: The sensory capabilities of the fish. Fish rely on both vision and on hydrodynamic signals relayed through its lateral line . Antarctic krill rely on vision and on hydrodynamic signals relayed through its antennae . Mucus Mucus ( / ˈ m j uː k ə s / , MEW -kəs ) is a slippery aqueous secretion produced by, and covering, mucous membranes . It is typically produced from cells found in mucous glands , although it may also originate from mixed glands, which contain both serous and mucous cells. It
11500-634: The shape of the school, without collisions. It is as if their motions are choreographed, though they are not. There must be very fast response systems to allow the fish to do this. Young fish practice schooling techniques in pairs, and then in larger groups as their techniques and senses mature. The schooling behaviour develops instinctively and is not learned from older fish. To school the way they do, fish require sensory systems which can respond with great speed to small changes in their position relative to their neighbour. Most schools lose their schooling abilities after dark, and just shoal. This indicates that vision
11615-430: The sharks compact schools of prey by swimming around them and splashing the water with their tails, often in pairs or small groups. Threshers swim in circles to drive schooling prey into a compact mass, before striking them sharply with the upper lobe of its tail to stun them. Spinner sharks charge vertically through the school, spinning on their axis with their mouths open and snapping all around. The shark's momentum at
11730-619: The shoal members, will be better than that taken by an individual fish. Forage fish often make great migrations between their spawning, feeding and nursery grounds. Schools of a particular stock usually travel in a triangle between these grounds. For example, one stock of herrings have their spawning ground in southern Norway , their feeding ground in Iceland , and their nursery ground in northern Norway. Wide triangular journeys such as these may be important because forage fish, when feeding, cannot distinguish their own offspring. Capelin are
11845-440: The shoaling fish. These sharks compact their prey school by swimming around them and splashing the water with their tails, often in pairs or small groups. They then strike them sharply with the upper lobe of their tails to stun them. Spinner sharks charge vertically through the school, spinning on their axes with their mouths open and snapping all around. The sharks' momentum at the end of these spiraling runs often carries them into
11960-480: The shoals, creating a feeding frenzy along the coastline. When threatened, sardines (and other forage fish) instinctively group together and create massive bait balls . Bait balls can be up to 20 metres (66 ft) in diameter. They are short lived, seldom lasting longer than 20 minutes. The fish eggs, left behind at the Agulhas Banks, drift north west with the current into waters off the west coast, where
12075-457: The size of the parent fish and also on the local race. Incubation time is about 40 days at 3 °C (37 °F), 15 days at 7 °C (45 °F), or 11 days at 10 °C (50 °F). Eggs die at temperatures above 19 °C (66 °F). The larvae are 5 to 6 mm ( 3 ⁄ 16 to 1 ⁄ 4 in) long at hatching, with a small yolk sac that is absorbed by the time the larvae reach 10 mm ( 13 ⁄ 32 in). Only
12190-418: The swimming and feeding energetics. Many hypotheses to explain the function of schooling have been suggested, such as better orientation, synchronized hunting, predator confusion and reduced risk of being found. Schooling also has disadvantages, such as excretion buildup in the breathing media and oxygen and food depletion. The way the fish array in the school probably gives energy saving advantages, though this
12305-414: The three dimensional structure of real world fish shoals because of the large number of fish involved. Techniques include the use of recent advances in fisheries acoustics . Parameters defining a fish shoal include: [REDACTED] Boids simulation – needs Java The observational approach is complemented by the mathematical modelling of schools. The most common mathematical models of schools instruct
12420-430: The tunability of swelling effect is controlled by polyelectrolyte effect. Polymers with charged molecules are called polyelectrolytes . Mucins, a kind of polyelectrolyte proteoglycans , are the main component of mucus, which provides the polyelectrolyte effect in mucus. The process of inducing this effect comprises two steps: attraction of counter-ions and water compensation. When exposed in physiological ionic solution,
12535-466: The viscous nasal or airway mucus and prevented from entering the system. This process, together with the continual movement of the cilia on the respiratory epithelium toward the oropharynx ( mucociliary clearance ), helps prevent foreign objects from entering the lungs during breathing. This explains why coughing often occurs in those who smoke cigarettes. The body's natural reaction is to increase mucus production. In addition, mucus aids in moisturizing
12650-439: The warm air meets the colder outside temperature near the nostrils. This causes an excess amount of water to build up inside nasal cavities. In these cases, the excess fluid usually spills out externally through the nostrils. In the lower respiratory tract impaired mucociliary clearance due to conditions such as primary ciliary dyskinesia may result in mucus accumulation in the bronchi. The dysregulation of mucus homeostasis
12765-477: The water at up to 100 kilometres per hour (60 mph). They have air sacs under their skin in their face and chest which act like bubble-wrap , cushioning the impact with the water. Subsets of bottlenose dolphin populations in Mauritania are known to engage in interspecific cooperative fishing with human fishermen. The dolphins drive a school of fish towards the shore where humans await with their nets. In
12880-413: The water. It uses receptors called neuromasts , each of which is composed of a group of hair cells. The hairs are surrounded by a protruding jelly-like cupula , typically 0.1 to 0.2 mm long. The hair cells in the lateral line are similar to the hair cells inside the vertebrate inner ear, indicating that the lateral line and the inner ear share a common origin. It is difficult to observe and describe
12995-572: The way that bicyclists may draft one another in a peloton . Geese flying in a Vee formation are also thought to save energy by flying in the updraft of the wingtip vortex generated by the previous animal in the formation. Increased efficiencies in swimming in groups have been proposed for schools of fish and Antarctic krill . It would seem reasonable to think that the regular spacing and size uniformity of fish in schools would result in hydrodynamic efficiencies. While early laboratory-based experiments failed to detect hydrodynamic benefits created by
13110-517: The whale accelerates from below a bait ball to a high velocity and then opens its mouth to a large gape angle. This generates the water pressure required to expand its mouth and engulf and filter a huge amount of water and fish. Lunge feeding by the huge rorquals is said to be the largest biomechanical event on Earth. Fish schools swim in disciplined phalanxes, with some species, such as herrings, able to stream up and down at impressive speeds, twisting this way and that, and making startling changes in
13225-441: Was demonstrated by Pitcher and others in their study of foraging behaviour in shoaling cyprinids . In this study, the time it took for groups of minnows and goldfish to find a patch of food was quantified. The number of fishes in the groups was varied, and a statistically significant decrease in the amount of time necessary for larger groups to find food was established. Further support for an enhanced foraging capability of schools
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