A fishery is an entity engaged in raising or harvesting fish, determined by some authority to be a fishery. According to the FAO, a fishery is defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats, purpose of the activities or a combination of the foregoing features"; the definition includes a combination of fish and fishers in a region, the latter fishing for similar species with similar gear types. A fishery may involve the capture of wild fish or raising fish through fish aquaculture. Directly or indirectly, the livelihood of over 500 million people in developing countries depends on fisheries and aquaculture. Overfishing, including the taking of fish beyond sustainable levels, is reducing fish stocks and employment in many world regions. A report by Prince Charles' International Sustainability Unit, the New York-based Environmental Defence Fund and 50in10 published in July 2014 estimated global fisheries were adding $270 billion a year to global GDP, but by full implementation of sustainable fishing, that figure could rise by as much as $50 billion.
In biology – the term fish is most used to describe any animal with a backbone that has gills throughout life and has limbs, if any, in the shape of fins. Many types of aquatic animals referred to as fish are not fish in this strict sense. In earlier times biologists did not make a distinction—sixteenth century natural historians classified seals, amphibians, crocodiles hippopotamuses, as well as a host of marine invertebrates, as fish. In fisheries – the term fish is used as a collective term, includes mollusks and any aquatic animal, harvested. True fish – The strict biological definition of a fish, above, is sometimes called a true fish. True fish are referred to as finfish or fin fish to distinguish them from other aquatic life harvested in fisheries or aquaculture. Fisheries are harvested for their value, they can be freshwater, wild or farmed. Examples are the salmon fishery of Alaska, the cod fishery off the Lofoten islands, the tuna fishery of the Eastern Pacific, or the shrimp farm fisheries in China.
Capture fisheries can be broadly classified as industrial scale, small-scale or artisanal, recreational. Close to 90 % of the world's fishery catches come from seas, as opposed to inland waters; these marine catches have remained stable since the mid-nineties. Most marine fisheries are based near the coast; this is not only because harvesting from shallow waters is easier than in the open ocean, but because fish are much more abundant near the coastal shelf, due to the abundance of nutrients available there from coastal upwelling and land runoff. However, productive wild fisheries exist in open oceans by seamounts, inland in lakes and rivers. Most fisheries are wild fisheries. Farming can occur in coastal areas, such as with oyster farms, but more occur inland, in lakes, ponds and other enclosures. There are species fisheries worldwide for finfish, mollusks and echinoderms, by extension, aquatic plants such as kelp. However, a small number of species support the majority of the world's fisheries.
Some of these species are herring, anchovy, flounder, squid, salmon, lobster and scallops. All except these last four provided a worldwide catch of well over a million tonnes in 1999, with herring and sardines together providing a harvest of over 22 million metric tons in 1999. Many other species are harvested in smaller numbers. Cullis-Suzuki S and Pauly D "Failing the high seas: A global evaluation of regional fisheries management organizations" Marine Policy, 34 pp 1036–1042. FAO: Types of fisheries Hart PJB and Reynolds JD Handbook of fish biology and fisheries Wiley-Blackwell. ISBN 978-0-632-05412-1 Fisheries at Curlie FAO Fisheries Department and its SOFIA report The Fishery Resources Monitoring System The International Institute of Fisheries Economics and Trade Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, Future Options, U. S. National Academy of Sciences UNEP/GEF South China Sea Project and its Fisheries Refugia Portal and National Reports on Fish Stocks and Habitats in the South China Sea World Fisheries Day: Seafood for Thought and World Fisheries from Sea to Table slideshow on the Smithsonian Ocean Portal Hawes, J. W..
"Fisheries". The American Cyclopædia. "Fisheries". New International Encyclopedia. 1905. Fisheries Wiki A detailed online encyclopaedia providing current and quantitative information on marine fisheries worldwide
Fish anatomy is the study of the form or morphology of fishes. It can be contrasted with fish physiology, 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, the latter dealing with how those components function together in living fish; the anatomy of fish is shaped by the physical characteristics of water, the medium in which fish live. Water is much denser than air, holds a small amount of dissolved oxygen, absorbs more light than air does; the body of a fish is divided into a head 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. 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 have only local vision. There is an inner ear but no 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, 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 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 genital passages open, but not a swim bladder. Cartilaginous fish produce a small number of 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 with major evolutionary changes from the features of ancient fish, they have a bony skeleton, are laterally flattened, have five pairs of gills protected by an operculum, 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 spawn a large number of small eggs with little yolk which they broadcast into the water column. In many respects fish anatomy is different from humans and mammals, yet it shares the same basic vertebrate body plan from which all vertebrates have evolved: a notochord, rudimentary vertebrae, a well-defined head and tail.
Fish have a variety of different body plans. At the broadest level their body is divided into head and tail, although the divisions are not always externally visible; the body is fusiform, a streamlined body plan found in fast-moving fish. They may be filiform or vermiform. Fish are either compressed or depressed. There are two different skeletal types: the exoskeleton, the stable outer shell of an organism, the endoskeleton, which forms the support structure inside the body; the skeleton of the fish is made of either bone. The main features of the fish, the fins, are bony fin rays and, except for the caudal fin, have no direct connection with the spine, they are supported only by the muscles. The ribs attach to the spine. Bones are rigid organs, they function to move and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Bones have a complex internal and external structure, they are lightweight, yet hard, in addition to fulfilling their many other functions.
Fish bones have been used to bioremediate lead from contaminated soil. Fish are vertebrates. All vertebrates are built along the basic chordate body plan: a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it and the gastrointestinal tract below. In all vertebrates, the mouth is found at, or right below, the anterior end of the animal, while the anus opens to the exterior before the end of the body; the remaining part of the body continuing aft of the anus forms a tail with vertebrae and spinal cord, but no gut. The defining characteristic of a vertebrate is the vertebral column, in which the notochord found in all chordates has been replaced by a segmented series of stiffer elements separated by mobile joints. However, a few fish have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon; the vertebral column consists of a centrum, vertebral arches which protrude from the top and bottom of the centrum, various processes which pr
Carp are various species of oily freshwater fish from the family Cyprinidae, a large group of fish native to Europe and Asia. The cypriniformes are traditionally grouped with the Characiformes and Gymnotiformes to create the superorder Ostariophysi, since these groups share some common features; these features include being found predominantly in fresh water and possessing Weberian ossicles, an anatomical structure derived from the first five anterior-most vertebrae, their corresponding ribs and neural crests. The third anterior-most pair of ribs is in contact with the extension of the labyrinth and the posterior with the swim bladder; the function is poorly understood, but this structure is presumed to take part in the transmission of vibrations from the swim bladder to the labyrinth and in the perception of sound, which would explain why the Ostariophysi have such a great capacity for hearing. Most cypriniformes have scales and teeth on the inferior pharyngeal bones which may be modified in relation to the diet.
Tribolodon is the only cyprinid genus. Several species return to fresh water to spawn. All of the other cypriniformes have a wide geographical range; some consider all cyprinid fishes carp, the family Cyprinidae itself is known as the carp family. In colloquial use, carp refers only to several larger cyprinid species such as Cyprinus carpio, Carassius carassius, Ctenopharyngodon idella, Hypophthalmichthys molitrix, Hypophthalmichthys nobilis. Carp have long been an important food fish to humans. Several species such as the various goldfish breeds and the domesticated common carp variety known as koi have been popular ornamental fishes; as a result, carp have been introduced to various locations, though with mixed results. Several species of carp are listed as invasive species by the U. S. Department of Agriculture, worldwide, large sums of money are spent on carp control. At least some species of carp are able to survive for months with no oxygen by metabolizing glycogen to form lactic acid, converted into ethanol and carbon dioxide.
The ethanol diffuses into the surrounding water through the gills. In 1653 Izaak Walton wrote in The Compleat Angler, "The Carp is the queen of rivers. Carp are variable in terms of angling value. In Europe when not fished for food, they are eagerly sought by anglers, being considered prized coarse fish that are difficult to hook; the UK has a thriving carp angling market. It is the fastest growing angling market in the UK, has spawned a number of specialised carp angling publications such as Carpology, Advanced carp fishing and Total Carp, informative carp angling web sites, such as Carpfishing UK. In the United States, carp are classified as a rough fish, as well as damaging to naturalized exotic species, but with sporting qualities. Carp have long suffered from a poor reputation in the United States as undesirable for angling or for the table since they are an invasive species out-competing more desirable local game fish. Nonetheless, many states' departments of natural resources are beginning to view the carp as an angling fish instead of a maligned pest.
Groups such as Wild Carp Companies, American Carp Society, the Carp Anglers Group promote the sport and work with fisheries departments to organize events to introduce and expose others to the unique opportunity the carp offers freshwater anglers. Various species of carp have been domesticated and reared as food fish across Europe and Asia for thousands of years; these various species appear to have been domesticated independently, as the various domesticated carp species are native to different parts of Eurasia. Aquaculture has been pursued in China for at least 2,400 years. A tract by Fan Li in the fifth century BC details many of the ways carp were raised in ponds; the common carp, Cyprinus carpio, is from Central Europe. Several carp species were domesticated in East Asia. Carp that are from South Asia, for example catla and mrigal, are known as Indian carp, their hardiness and adaptability have allowed domesticated species to be propagated all around the world. Although the carp was an important aquatic food item, as more fish species have become available for the table, the importance of carp culture in Western Europe has become less important.
Demand has declined due to the appearance of more desirable table fish such as trout and salmon through intensive farming, environmental constraints. However, fish production in ponds is still a major form of aquaculture in Central and Eastern Europe, including the Russian Federation, where most of the production comes from low or intermediate-intensity ponds. In Asia, the farming of carp continues to surpass the total amount of farmed fish volume of intensively sea-farmed species, such as salmon and tuna. Selective breeding programs for the common carp include improvement in growth and resistance to disease. Experiments carried out in the USSR used crossings of broodstocks to increase genetic diversity, selected the species for traits such as growth rate, exterior traits and viability, and/or adaptation to environmental conditions such as variations in temperature. Selected carp for fast growth and tolerance to cold, the Ropsha carp; the results showed a 30 to 77.4% improvement of cold tolerance, but did not provide any data for growth
Fishing is the activity of trying to catch fish. Fish are caught in the wild. Techniques for catching fish include hand gathering, netting and trapping. “Fishing” may include catching aquatic animals other than fish, such as molluscs, cephalopods and echinoderms. The term is not applied to catching farmed fish, or to aquatic mammals, such as whales where the term whaling is more appropriate. In addition to being caught to be eaten, fish are caught as recreational pastimes. Fishing tournaments are held, caught fish are sometimes kept as preserved or living trophies; when bioblitzes occur, fish are caught and released. According to the United Nations FAO statistics, the total number of commercial fishermen and fish farmers is estimated to be 38 million. Fisheries and aquaculture provide direct and indirect employment to over 500 million people in developing countries. In 2005, the worldwide per capita consumption of fish captured from wild fisheries was 14.4 kilograms, with an additional 7.4 kilograms harvested from fish farms.
Fishing is an ancient practice that dates back to at least the beginning of the Upper Paleolithic period about 40,000 years ago. Isotopic analysis of the skeletal remains of Tianyuan man, a 40,000-year-old modern human from eastern Asia, has shown that he consumed freshwater fish. Archaeology features such as shell middens, discarded fish bones, cave paintings show that sea foods were important for survival and consumed in significant quantities. Fishing in Africa is evident early on in human history. Neanderthals were fishing by about 200,000 BC to have a source of food for their families and to trade or sell. People could have developed basketry for fish traps, spinning and early forms of knitting in order to make fishing nets to be able to catch more fish in larger quantities. During this period, most people lived a hunter-gatherer lifestyle and were, of necessity on the move. However, where there are early examples of permanent settlements such as those at Lepenski Vir, they are always associated with fishing as a major source of food.
The British dogger was an early type of sailing trawler from the 17th century, but the modern fishing trawler was developed in the 19th century, at the English fishing port of Brixham. By the early 19th century, the fishermen at Brixham needed to expand their fishing area further than before due to the ongoing depletion of stocks, occurring in the overfished waters of South Devon; the Brixham trawler that evolved there was of a sleek build and had a tall gaff rig, which gave the vessel sufficient speed to make long distance trips out to the fishing grounds in the ocean. They were sufficiently robust to be able to tow large trawls in deep water; the great trawling fleet that built up at Brixham, earned the village the title of'Mother of Deep-Sea Fisheries'. This revolutionary design made large scale trawling in the ocean possible for the first time, resulting in a massive migration of fishermen from the ports in the South of England, to villages further north, such as Scarborough, Grimsby and Yarmouth, that were points of access to the large fishing grounds in the Atlantic Ocean.
The small village of Grimsby grew to become the largest fishing port in the world by the mid 19th century. An Act of Parliament was first obtained in 1796, which authorised the construction of new quays and dredging of the Haven to make it deeper, it was only in the 1846, with the tremendous expansion in the fishing industry, that the Grimsby Dock Company was formed. The foundation stone for the Royal Dock was laid by Albert the Prince consort in 1849; the dock covered 25 acres and was formally opened by Queen Victoria in 1854 as the first modern fishing port. The elegant Brixham trawler spread across the world. By the end of the 19th century, there were over 3,000 fishing trawlers in commission in Britain, with 1,000 at Grimsby; these trawlers were sold to fishermen including from the Netherlands and Scandinavia. Twelve trawlers went on to form the nucleus of the German fishing fleet; the earliest steam powered fishing boats first appeared in the 1870s and used the trawl system of fishing as well as lines and drift nets.
These were large boats 80–90 feet in length with a beam of around 20 feet. They travelled at 9 -- 11 knots; the earliest purpose built fishing vessels were designed and made by David Allan in Leith, Scotland in March 1875, when he converted a drifter to steam power. In 1877, he built. Steam trawlers were introduced at Hull in the 1880s. In 1890 it was estimated; the steam drifter was not used in the herring fishery until 1897. The last sailing fishing trawler was built in 1925 in Grimsby. Trawler designs adapted as the way they were powered changed from sail to coal-fired steam by World War I to diesel and turbines by the end of World War II. In 1931, the first powered drum was created by Laurie Jarelainen; the drum was a circular device, set to the side of the boat and would draw in the nets. Since World War II, radio navigation aids and fish finders have been used; the first trawlers fished over the side, rather than over the stern. The first purpose built stern trawler was Fairtry built in 1953 at Scotland.
The ship was much larger than any other trawlers in operation and inaugurated the era of the'super trawler'. As the ship pulled its nets over the stern, it could lift out a much greater haul of up to 60 tons; the ship served as a basis for the expansion of'su
Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the gill used for gas exchange. Rakers are present in two rows, projecting from both the anterior and posterior side of each gill arch. Rakers are varied in number and form. By preventing food particles from exiting the spaces between the gill arches, they enable the retention of food particles in filter feeders; the structure and spacing of gill rakers in fish determines the size of food particles trapped, correlates with feeding behavior. Fish with densely spaced, comb-like gill rakers are efficient at filtering tiny prey, whereas carnivores and omnivores have more spaced gill rakers with secondary projections; because gill raker characters vary between related taxa, they are used in the classification and identification of fish species. Much of the variation in gill raker morphology is thought to be due to adaptation to optimize the consumption of different diets.
To prevent the damaging passage of solid material through the gill slits and over the gill filaments, early gill rakers strained large particles from the water and diverted them to the esophagus. Since an appreciable fraction of this material was nutritious, rakers subsequently evolved as food-trapping mechanisms in filter feeders. Gill rakers, when long and set, play the same role in suspension-feeding fish such as mullet, megamouth and whale sharks, as baleen in the filter-feeding whales
Age determination in fish
Knowledge of fish age characteristics is necessary for stock assessments, to develop management or conservation plans. Size is associated with age. Therefore, researchers interested in determining a fish age look for structures which increase incrementally with age; the most used techniques involve counting natural growth rings on the scales, vertebrate, fin spines, eye lenses, teeth, or bones of the jaw, pectoral girdle, opercular series. Reliable aging techniques may vary among species. Aristotle may have been the first scientist to speculate on the use of hard parts of fishes to determine age, stating in Historica Animalium that “the age of a scaly fish may be told by the size and hardness of its scales.” However, it wasn't until the development of the microscope that more detailed studies were performed on the structure of scales. Antonie van Leeuwenhoek developed improved lenses, he had a wide range of interests including the structure of fish scales from the European eel and the burbot, species which were thought not to have scales.
He observed that the scales contained “circular lines” and that each scale had the same number of these lines, inferred that the number of lines correlated to the age of the fish. He correctly associated the darker areas of scale growth to the season of slowed growth, a characteristic he had observed in tree trunks. Leeuwenhoek's work went undiscovered by fisheries researchers, the discovery of fish aging structures is credited to Hans Hederström. Hederström examined the vertebrae of pike and concluded that each contained growth rings which could be used to determine the fish's age. In 1859, Robert Bell reported that one could use these growth rings to reliably determine the age of all fish after examination of sucker vertebrae and yellow perch scales that he raised in a pond for two years showed “two rings or circles.” In 1898, more than 200 years after Leewenhoek's original insights of scale age structure, this subject was given a thorough review by C. Hoffbauer. Hoffbauer studied, he noted that during the season of growth, the concentric rings were discernible and spaced.
His work convinced other researchers. Shortly after Hoffbauer's findings were published, structures other than scales were examined for utility of aging fish. Johannes Reibisch, working for the Commission of Scientific Investigation of German Seas at Kiel, attempted to use Hoffbauer's techniques to age plaice but found it difficult to discern annuli, he decided to study a different structure and in 1899 he published the first procedures using otoliths as an aging structure. A fellow scientist with the German Commission at Kiel, Friedriche Heincke frustrated with difficult scale annuli, further studied other structures to age fish, he discovered annuli in the vertebrae and pectoral girdle and published his findings in Heicke 1905. The works of Hoffbauer and Heinke are most cited as establishing scales and bony structures as viable aging structures. Further, Tereshenko is credited as the first to use cleithra aging techniques on roach. Not long after Hoffbauer's and Reibisch's findings were published, aging was used in fishery assessments of the early 1900s.
One of the first to focus on the applications of fish aging was the Norwegian fisheries scientist Johan Hjort. Focusing on fish scales, Hjort developed an extensive aging program collecting statistics on birth rate, age-distribution and migration. Hjort's research elicited debate from the biomathematician D’Arcy Wentworth Thompson, who rescinded his criticisms, his research otherwise received glowing praise and would lead to fundamental changes in the way fish populations were studied and managed. Scales are the most used aging structure in North America because of their non-lethal ease of collection. Counting the number of annuli on a scale provides the fish age and the spacing between rings is proportional to the growth of the fish. For some examples and uses of scale aging you can go to "Fish scales tell a story..." from the Delaware Division of Fish & Wildlife. The ease of collection of this aging structure is not without its tradeoffs, as the major bias of scales used as an age estimation structure is their tendency to underestimate the age of older fish.
The general process for scale age analysis preparation is. During collection, it is important to make sure to sample the same area on the same side of each individual. Insert the scale into a scale envelope press on acetate slides or it can be washed in distilled water and rubbed between the fingers. Mount the scale on glass slides and dry in moderate heat, 37˚C or 100˚ F; the annuli may be counted using microfilm reader, or other such magnification device. Fish otoliths are present in pairs; these three pairs of otoliths in teleost fishes differ in
The zebrafish is a freshwater fish belonging to the minnow family of the order Cypriniformes. Native to South Asia, it is a popular aquarium fish sold under the trade name zebra danio; the zebrafish is an important and used vertebrate model organism in scientific research, for example in drug development, in particular pre-clinical development. It is notable for its regenerative abilities, has been modified by researchers to produce many transgenic strains; the zebrafish is a derived member of the family Cyprinidae. It has a sister-group relationship with Danio aesculapii. Zebrafish are closely related to the genus Devario, as demonstrated by a phylogenetic tree of close species; the zebrafish was referred to in scientific literature as Brachydanio rerio for many years until its reassignment to the genus Danio. The zebrafish is native to fresh water habitats in South Asia where it is found in India, Bangladesh and Bhutan; the northern limit is in the South Himalayas, ranging from the Sutlej river basin in the Pakistan–India border region to the state of Arunachal Pradesh in northeast Indian.
Its range is concentrated in the Ganges and Brahmaputra River basins, the species was first described from Kosi River of India. Its range further south is more local, with scattered records from the Western and Eastern Ghats regions, it has been said to occur in Myanmar, but this is based on old records and refers to close relatives only described notably Danio kyathit. Old records from Sri Lanka are questionable and remain unconfirmed. Zebrafish have been introduced to California, Connecticut and New Mexico in the United States by deliberate release by aquarists or by escape from fish farms; the New Mexico population had been extirpated by 2003 and it is unclear if the others survive, as the last published records were decades ago. Elsewhere the species has been introduced to Malaysia. Zebrafish inhabit medium-flowing to stagnant clear water of quite shallow depth in streams, ditches, oxbow lakes and rice paddies. There is some vegetation, either submerged or overhanging from the banks, the bottom is sandy, muddy or silty mixed with pebbles or gravel.
In surveys of zebrafish locations throughout much of its Bangladeshi and Indian distribution, the water had a near-neutral to somewhat basic pH and ranged from 16.5 to 34 °C in temperature. One unusually cold site was only 12.3 °C and another unusually warm site was 38.6 °C, but the zebrafish still appeared healthy. The unusually cold temperature was at one of the highest known zebrafish locations at 1,576 m above sea level, although the species has been recorded to 1,795 m; the zebrafish is named for the five uniform, horizontal, blue stripes on the side of the body, which are reminiscent of a zebra's stripes, which extend to the end of the caudal fin. Its shape is laterally compressed, with its mouth directed upwards; the male is torpedo-shaped, with gold stripes between the blue stripes. Adult females exhibit a small genital papilla in front of the anal fin origin; the zebrafish can reach up to 4–5 cm in length, although they are 1.8–3.7 cm in the wild with some variations depending on location.
Its lifespan in captivity is around two to three years, although in ideal conditions, this may be extended to over five years. In the wild it is an annual species. In 2015, a study was published about zebrafishes' capacity for episodic memory; the individuals showed a capacity to remember context with respect to objects and occasions. Episodic memody is a capacity of explicit memory systems associated with conscious experience; the approximate generation time for Danio rerio is three months. A male must be present for spawning to occur. Females are able to spawn at intervals of two to three days. Upon release, embryonic development begins. Fertilized eggs immediately become transparent, a characteristic that makes D. rerio a convenient research model species. The zebrafish embryo develops with precursors to all major organs appearing within 36 hours of fertilization; the embryo begins as a yolk with a single enormous cell on top, which divides into two and continues dividing until there are thousands of small cells.
The cells migrate down the sides of the yolk and begin forming a head and tail. The tail grows and separates from the body; the yolk shrinks over time because the fish uses it for food as it matures during the first few days. After a few months, the adult fish reaches reproductive maturity. To encourage the fish to spawn, some researchers use a fish tank with a sliding bottom insert, which reduces the depth of the pool to simulate the shore of a river. Zebrafish spawn best in the morning due to their Circadian rhythms. Researchers have been able to collect 10,000 embryos in 10 minutes using this method. Male zebrafish are furthermore known to respond to more pronounced markings on females, i.e. "good stripes", but in a group, males will mate with whichever females they can find. What attracts females is not understood; the presence of plants plastic pl