Wetland
A wetland is a distinct ecosystem, inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, support of plants and animals. Wetlands are considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for assessing these functions, wetland ecological health, general wetland condition have been developed in many regions and have contributed to wetland conservation by raising public awareness of the functions and the ecosystem services some wetlands provide.
Wetlands occur on every continent. The main wetland types are swamp, marsh and fen. Many peatlands are wetlands; the water in wetlands is either brackish, or saltwater. Wetlands can be non-tidal; the largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, the Sundarbans in the Ganges-Brahmaputra delta. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff, they may play a role in water-sensitive urban design. A patch of land that develops pools of water after a rain storm would not be considered a "wetland" though the land is wet. Wetlands have unique characteristics: they are distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants.
A more concise definition is a community composed of hydric soil and hydrophytes. Wetlands have been described as ecotones, providing a transition between dry land and water bodies. Mitsch and Gosselink write that wetlands exist "...at the interface between terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet dependent on both."In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. A wetland is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota rooted plants, to adapt to flooding." There are four main kinds of wetlands – marsh, swamp and fen. Some experts recognize wet meadows and aquatic ecosystems as additional wetland types; the largest wetlands in the world include the swamp forests of the Amazon and the peatlands of Siberia. Under the Ramsar international wetland conservation treaty, wetlands are defined as follows: Article 1.1: "...wetlands are areas of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water, static or flowing, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."
Article 2.1: " may incorporate riparian and coastal zones adjacent to the wetlands, islands or bodies of marine water deeper than six metres at low tide lying within the wetlands." Although the general definition given above applies around the world, each county and region tends to have its own definition for legal purposes. In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands include swamps, marshes and similar areas"; this definition has been used in the enforcement of the Clean Water Act. Some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal government's. In the United States Code, the term wetland is defined "as land that has a predominance of hydric soils, is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation adapted for life in saturated soil conditions and under normal circumstances supports a prevalence of such vegetation."
Related to this legal definitions, the term "normal circumstances" are conditions expected to occur during the wet portion of the growing season under normal climatic conditions, in the absence of significant disturbance. It is not uncommon for a wetland to be dry for long portions of the growing season. Wetlands can be dry during the dry season and abnormally dry periods during the wet season, but under normal environmental conditions the soils in a wetland will be saturated to the surface or inundated such that the soils become anaerobic, those conditions will persist through the wet portion of the growing season; the most important factor producing wetlands is flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation
Salt
Salt is a mineral composed of sodium chloride, a chemical compound belonging to the larger class of salts. Salt is present in vast quantities in seawater; the open ocean has about 35 grams of solids per liter of sea water, a salinity of 3.5%. Salt is essential for life in general, saltiness is one of the basic human tastes. Salt is one of the oldest and most ubiquitous food seasonings, salting is an important method of food preservation; some of the earliest evidence of salt processing dates to around 6,000 BC, when people living in the area of present-day Romania boiled spring water to extract salts. Salt was prized by the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and the Indians. Salt became an important article of trade and was transported by boat across the Mediterranean Sea, along specially built salt roads, across the Sahara on camel caravans; the scarcity and universal need for salt have led nations to go to war over it and use it to raise tax revenues. Salt has other cultural and traditional significance.
Salt is processed from salt mines, by the evaporation of seawater and mineral-rich spring water in shallow pools. Its major industrial products are caustic chlorine. Of the annual global production of around two hundred million tonnes of salt, about 6% is used for human consumption. Other uses include water conditioning processes, de-icing highways, agricultural use. Edible salt is sold in forms such as sea salt and table salt which contains an anti-caking agent and may be iodised to prevent iodine deficiency; as well as its use in cooking and at the table, salt is present in many processed foods. Sodium is an essential nutrient for human health via its role as an osmotic solute. Excessive salt consumption may increase the risk of cardiovascular diseases, such as hypertension, in children and adults; such health effects of salt have long been studied. Accordingly, numerous world health associations and experts in developed countries recommend reducing consumption of popular salty foods; the World Health Organization recommends that adults should consume less than 2,000 mg of sodium, equivalent to 5 grams of salt per day.
All through history, the availability of salt has been pivotal to civilization. What is now thought to have been the first city in Europe is Solnitsata, in Bulgaria, a salt mine, providing the area now known as the Balkans with salt since 5400 BC; the name Solnitsata means "salt works". While people have used canning and artificial refrigeration to preserve food for the last hundred years or so, salt has been the best-known food preservative for meat, for many thousands of years. A ancient salt-works operation has been discovered at the Poiana Slatinei archaeological site next to a salt spring in Lunca, Neamț County, Romania. Evidence indicates that Neolithic people of the Precucuteni Culture were boiling the salt-laden spring water through the process of briquetage to extract the salt as far back as 6050 BC; the salt extracted from this operation may have had a direct correlation to the rapid growth of this society's population soon after its initial production began. The harvest of salt from the surface of Xiechi Lake near Yuncheng in Shanxi, dates back to at least 6000 BC, making it one of the oldest verifiable saltworks.
There is more salt in animal tissues, such as meat and milk, than in plant tissues. Nomads who subsist on their flocks and herds do not eat salt with their food, but agriculturalists, feeding on cereals and vegetable matter, need to supplement their diet with salt. With the spread of civilization, salt became one of the world's main trading commodities, it was of high value to the ancient Hebrews, the Greeks, the Romans, the Byzantines, the Hittites and other peoples of antiquity. In the Middle East, salt was used to ceremonially seal an agreement, the ancient Hebrews made a "covenant of salt" with God and sprinkled salt on their offerings to show their trust in him. An ancient practice in time of war was salting the earth: scattering salt around in a defeated city to prevent plant growth; the Bible tells the story of King Abimelech, ordered by God to do this at Shechem, various texts claim that the Roman general Scipio Aemilianus Africanus ploughed over and sowed the city of Carthage with salt after it was defeated in the Third Punic War.
Salt may have been used for barter in connection with the obsidian trade in Anatolia in the Neolithic Era. Salt was included among funeral offerings found in ancient Egyptian tombs from the third millennium BC, as were salted birds, salt fish. From about 2800 BC, the Egyptians began exporting salt fish to the Phoenicians in return for Lebanon cedar and the dye Tyrian purple. Herodotus described salt trading routes across Libya back in the 5th century BC. In the early years of the Roman Empire, roads were built for the transportation of salt from the salt imported at Ostia to the capital. In Africa, salt was used as currency south of the Sahara, slabs of rock salt were used as coins in Abyssinia. Moorish merchants in the 6th century traded salt for weight for weight; the Tuareg have traditionally maintained routes across the Sahara for the transportation of salt by Azalai. The caravans
Ecosystem
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment, interacting as a system. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy is incorporated into plant tissue. By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the system, they influence the quantity of plant and microbial biomass present. By breaking down dead organic matter, decomposers release carbon back to the atmosphere and facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be used by plants and other microbes. Ecosystems are controlled by internal factors. External factors such as climate, the parent material which forms the soil and topography, control the overall structure of an ecosystem, but are not themselves influenced by the ecosystem. Ecosystems are dynamic entities—they are subject to periodic disturbances and are in the process of recovering from some past disturbance.
Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present. Internal factors not only control ecosystem processes but are controlled by them and are subject to feedback loops. Resource inputs are controlled by external processes like climate and parent material. Resource availability within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Although humans operate within ecosystems, their cumulative effects are large enough to influence external factors like climate. Biodiversity affects ecosystem functioning, as do the processes of disturbance and succession. Ecosystems provide a variety of services upon which people depend; the term ecosystem was first used in 1935 in a publication by British ecologist Arthur Tansley. Tansley devised the concept to draw attention to the importance of transfers of materials between organisms and their environment.
He refined the term, describing it as "The whole system... including not only the organism-complex, but the whole complex of physical factors forming what we call the environment". Tansley regarded ecosystems not as natural units, but as "mental isolates". Tansley defined the spatial extent of ecosystems using the term ecotope. G. Evelyn Hutchinson, a limnologist, a contemporary of Tansley's, combined Charles Elton's ideas about trophic ecology with those of Russian geochemist Vladimir Vernadsky; as a result, he suggested. This would, in turn, limit the abundance of animals. Raymond Lindeman took these ideas further to suggest that the flow of energy through a lake was the primary driver of the ecosystem. Hutchinson's students, brothers Howard T. Odum and Eugene P. Odum, further developed a "systems approach" to the study of ecosystems; this allowed them to study the flow of material through ecological systems. Ecosystems are controlled both by internal factors. External factors called state factors, control the overall structure of an ecosystem and the way things work within it, but are not themselves influenced by the ecosystem.
The most important of these is climate. Climate determines the biome. Rainfall patterns and seasonal temperatures influence photosynthesis and thereby determine the amount of water and energy available to the ecosystem. Parent material determines the nature of the soil in an ecosystem, influences the supply of mineral nutrients. Topography controls ecosystem processes by affecting things like microclimate, soil development and the movement of water through a system. For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. Other external factors that play an important role in ecosystem functioning include time and potential biota; the set of organisms that can be present in an area can significantly affect ecosystems. Ecosystems in similar environments that are located in different parts of the world can end up doing things differently because they have different pools of species present; the introduction of non-native species can cause substantial shifts in ecosystem function.
Unlike external factors, internal factors in ecosystems not only control ecosystem processes but are controlled by them. They are subject to feedback loops. While the resource inputs are controlled by external processes like climate and parent material, the availability of these resources within the ecosystem is controlled by internal factors like decomposition, root competition or shading. Other factors like disturbance, succession or the types of species present are internal factors. Primary production is the production of organic matter from inorganic carbon sources; this occurs through photosynthesis. The energy incorporated through this process supports life on earth, while the carbon makes up much of the organic matter in living and dead biomass, soil carbon and fossil fuels, it drives the carbon cycle, which influences global climate via the greenhouse effect. Through the process of photosynthesis, plants capture energy from light and use it to combine carbon dioxide and water to produce carbohydrates and oxygen.
The photosynthesis carried out by all the plants in an ecosystem is called the gross primary production. About half of the GPP is consumed in plant respiration; the remainder, that portion of GPP, not used up by respirati
Blue sucker
The blue sucker is a freshwater species of fish in the sucker family. The species has an average length of 76 centimeters; the record length has been recorded at 102 centimeters. Color is variable, from light steel-gray to jet black in the spring; the fish is streamlined, with an inferior mouth and a small/slender head that tapers to a fleshy snout. The mouth location allows the fish to feed off the bottom of its habitat; the body of this fish is elongated and compressed. It has a long falcate dorsal fin, elevated anterior with 24-35 rays, it has a forked caudal fin. The anal fin contains 7-8 rays on average; the scales contain 55-58 along the lateral line. The Blue Sucker is native to the United States and Mexico. In the U. S. it lives in the Mississippi River basin north to Wisconsin. The Blue Sucker lives in the Missouri River drainage to North Dakota and South Dakota and Montana; this species can be found in the Gulf drainage from the Sabine River to the Rio grande. Huge migrations of these fast, powerful fish once migrated throughout the Mississippi River basin, spring harvests of blue sucker were a staple food for early pioneers.
Blue suckers are rare today, thought to be due to the segmentation of habitat caused by the thousands of dams which have been built in the last century. Blues frequent the thalweg of large river systems, in heavy current. Blue suckers obtain their food off the bottom of rivers and other bodies of freshwater through a mouth in the inferior position; some organisms that they eat are aquatic insect larvae, plant materials and algae. The Blue Sucker has a spawning time from around March until June; this varies on the location of the fish and the water temperature. Fifty-three degrees is the average water temperature in which males and females find their spawning area; this area is in fast moving water around two feet deep. Rocks in the area will be larger than gravel, but they will be smaller than boulders; the peak water temperature is sixty-two degrees and the actual spawning time will last around two weeks. Male suckers will continue to come to the area until spawning is over. Females will go to the area, lay her eggs, leave once she is finished and they have been fertilized.
The Blue Sucker is sensitive to water pollution, is only able to live in water, well irrigated or pollution-less. This is; the species is listed as least concern. The Blue Sucker goes by the name blackhorse, the bluefish, the muskellunge, the razor back, the sockerel, the gourd seed sucker, the Missouri Sucker, the slenderhead sucker, the sweet sucker. "Cycleptus" is a Greek word meaning slender. "Elongatus" is a Latin word meaning elongated. Froese and Pauly, eds.. "Cycleptus elongatus" in FishBase. November 2005 version. NatureServe - Cycleptus elongatus Fishes of Minnesota - Blue sucker roughfish.com - Blue sucker Rines, George Edwin, ed.. "Blackhorse". Encyclopedia Americana
Common carp
The common carp or European carp is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia. The native wild populations are considered vulnerable to extinction by the International Union for Conservation of Nature, but the species has been domesticated and introduced into environments worldwide, is considered a destructive invasive species, being included in the list of the world's 100 worst invasive species, it gives its name to the carp family Cyprinidae. The two subspecies are: C. c. carpio is native to much of Europe. C. c. yilmaz is from Anatolian Turkey. A third subspecies, C. c. haematopterus native to eastern Asia, was recognized in the past, but recent authorities treat it as a separate species under the name C. rubrofuscus. The common carp and various Asian relatives in the pure forms can be separated by meristics and differ in genetics, but they are able to interbreed. Common carp can interbreed with the common goldfish; the common carp is native to Europe and Asia, has been introduced to every part of the world except the poles.
They are the third most introduced species worldwide, their history as a farmed fish dates back to Roman times. Carp are used as food in many areas, but are regarded as a pest in several regions due to their ability to out-compete native fish stocks; the original common carp was found in the inland delta of the Danube River about 2000 years ago, was torpedo-shaped and golden-yellow in colour. It had two pairs of a mesh-like scale pattern. Although this fish was kept as an exploited captive, it was maintained in large, specially built ponds by the Romans in south-central Europe; as aquaculture became a profitable branch of agriculture, efforts were made to farm the animals, the culture systems soon included spawning and growing ponds. The common carp's native range extends to the Black Sea, Caspian Sea and Aral Sea. Both European and Asian subspecies have been domesticated. In Europe, domestication of carp as food fish was spread by monks between the 13th and 16th centuries; the wild forms of carp had reached the delta of the Rhine in the 12th century with some human help.
Variants that have arisen with domestication include the mirror carp, with large, mirror-like scales, the leather carp, the scaled carp. Koi carp is a domesticated ornamental variety that originated in the Niigata region of Japan in the 1820s, but its parent species are the East Asian carp C. rubrofuscus. Wild common carp are slimmer than domesticated forms, with body length about four times body height, red flesh, a forward-protruding mouth. Common carp can grow to large sizes if given adequate space and nutrients, their average growth rate by weight is about half the growth rate of domesticated carp They do not reach the lengths and weights of domesticated carp, which can grow to a maximum length of 120 centimetres, a maximum weight of over 40 kilograms, an oldest recorded age of 38 years. The largest recorded carp, caught by an angler in January 2010 at Lac de curtons near Bordeaux, weighed 42.6 kilograms. The largest recorded carp, caught by British angler, Colin Smith, in 2013 at Etang La Saussaie Fishery, weighed 45.59 kilograms.
The average size of the common carp is around 40 -- 2 -- 14 kg. Although tolerant of most conditions, common carp prefer large bodies of slow or standing water and soft, vegetative sediments; as schooling fish, they prefer to be in groups of five or more. They live in temperate climates in fresh or brackish water with a pH of 6.5–9.0 and salinity up to about 0.5%, temperatures of 3 to 35 °C. The ideal temperature is 23 to 30 °C, with spawning beginning at 17 to 18 °C. Carp are able to tolerate water with low oxygen levels, by gulping air at the surface. Common carp are omnivorous, they can eat a herbivorous diet of aquatic plants, but prefer to scavenge the bottom for insects, crustaceans and benthic worms. An egg-layer, a typical adult female can lay 300,000 eggs in a single spawn. Although carp spawn in the spring, in response to rising water temperatures and rainfall, carp can spawn multiple times in a season. In commercial operations, spawning is stimulated using a process called hypophysation, where lyophilized pituitary extract is injected into the fish.
The pituitary extract contains gonadotropic hormones which stimulate gonad maturation and sex steroid production promoting reproduction. A single carp can lay over a million eggs in a year, yet their population remains the same, so the eggs and young perish in vast numbers. Eggs and fry fall victim to bacteria and the vast array of tiny predators in the pond environment. Carp which survive to juvenile are preyed upon by other fish such as the northern pike and largemouth bass, a number of birds and mammals. Common carp have been introduced to some 59 countries. In abs
United States
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Paddlefish
Paddlefish are basal Chondrostean ray-finned fish. They have been referred to as "primitive fish" because they have evolved with few morphological changes since the earliest fossil records of the Late Cretaceous, seventy to seventy-five million years ago. Polyodontids are North American and Chinese. There are six known species: four extinct species known only from fossil remains, two extant species, including the American paddlefish, native to the Mississippi River basin in the U. S. and the critically endangered Chinese paddlefish, endemic to the Yangtze River Basin in China. Chinese paddlefish are commonly referred to as "Chinese swordfish", or "elephant fish". Paddlefish populations have declined throughout their historic range as a result of overfishing and the encroachment of human development, including the construction of dams that have blocked their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed natural flows resulting in the loss of spawning habitat and nursery areas.
Chinese paddlefish have not been seen since 2007, may now be extinct for many of the same reasons that have plagued the American species. During the initial stages of development from embryo to fry, paddlefish have no rostrum, it begins to form shortly after hatching. The rostrum of a Chinese paddlefish is narrow and sword-like while the rostrum of the American paddlefish is broad and paddle-like; some common morphological characteristics of paddlefish include a spindle-shaped, smooth skinned scaleless body, heterocercal tail, small poorly developed eyes. Unlike the filter-feeding American paddlefish, Chinese paddlefish are piscivores, predaceous, their jaws are more forward pointing which suggest they forage on small fishes in the water column, on shrimp, benthic fishes, crabs. The jaws of the American paddlefish are distinctly adapted for filter feeding only, they are ram suspension filter feeders with a diet that consists of zooplankton, small insects, insect larvae, small fish. The largest Chinese paddlefish on record measured 23 ft in length, was estimated to weigh a few thousand pounds.
They reach 9.8 ft and 1,100 lb. Although the American paddlefish is one of the largest freshwater fishes in North America, their recorded lengths and weights fall short in comparison to the larger Chinese paddlefish. American paddlefish reach 5 ft or more in length and can weigh more than 60 lb; the largest American paddlefish on record was caught in 1916 in Iowa. The fish was taken with a spear, measured 7 ft 1 in long and 45.5 in in the girth. A report published by J. R. Harlan and E. B. Speaker in Iowa Fish and Fishing said; the world record paddlefish caught on rod and reel was 54.25 in long. The fish was caught by Clinton Boldridge in a 5-acre pond in Kansas. Scientists once believed paddlefish used their rostrums to excavate bottom substrate, but have since determined with the aid of electron microscopy that paddlefish have electroreceptors on their rostrum's ampulla which are similar in structure to other Lorenzini; the electroreceptors can detect weak electrical fields which not only signal the presence of prey items in the water column, such as zooplankton, the primary diet of the American paddlefish, but they can detect the individual feeding and swimming movements of zooplankton's appendages.
Paddlefish have poorly developed eyes, rely on their electroreceptors for foraging. However, the rostrum is not the paddlefish's sole means of food detection; some reports incorrectly suggest that a damaged rostrum would render paddlefish less capable of foraging efficiently to maintain good health. Laboratory experiments, field research indicate otherwise. In addition to electroreceptors on the rostrum, paddlefish have sensory pores covering nearly half of the skin surface extending from the rostrum to the top of the head down to the tips of the operculum. Therefore, paddlefish with damaged or abbreviated rostrums are still able to forage and maintain good health. Over the past half century, paddlefish populations have been on the decline. Attributable causes are overfishing and the encroachment of human development, including the construction of dams which block their seasonal upward migration to ancestral spawning grounds. Other detrimental effects include alterations of rivers which have changed the natural flow, resulted in the loss of spawning habitat and nursery areas.
American paddlefish have been extirpated from much of their Northern peripheral range, including the Great Lakes and Canada, New York and Pennsylvania. There is growing concern about their populations in other states; the Chinese paddlefish is considered anadromous with upstream migration, however little is known about their migration habits and population structure. They are endemic to the Yangtze River Basin in China where they lived in the broad surfaced main stem rivers and shoal zones along the East China Sea. Research suggests they preferred to navigate the middle and lower layers of the water column, swam into large lakes. Chinese paddlefish are now believed to be extinct as there have been no sightings of specimens in the wild since 2003, past attempts of artificial propagation for restoration purposes have failed because of difficulties encountered in keeping captive fish alive. American
