|
Lake Sturgeon
The lake sturgeon (''Acipenser fulvescens''), also known as the rock sturgeon, is a North American temperate freshwater fish, one of about 25 species of sturgeon. Like other sturgeons, this species is a bottom feeder with evolutionarily basal traits among fish, reflecting its early divergence from the shark lineage. These traits include a partly cartilaginous skeleton, an overall streamlined shape, and skin bearing rows of bony plates on the sides and back. The lake sturgeon uses its elongated, spade-like snout to stir up the substrate and sediments on the beds of rivers and lakes to feed. Four sensory organs ( barbels) hang near its mouth to help the sturgeon locate bottom-dwelling prey. Lake sturgeons can grow to a large size for freshwater fish, topping 7.25 ft (2.2 m) long and 240 lb (108 kg). Description The lake sturgeon has taste buds on and around its barbels near its rubbery, prehensile lips. It extends its lips to vacuum up soft live food, which it sw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek grc, label=none, πλεῖστος, pleīstos, most and grc, label=none, καινός, kainós (latinized as ), 'new'. At the end of the preceding Pliocene, the previously isolated North and South American continents were joined by the Isthmus of Panama, causing Great American Interchang ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North Saskatchewan
The North Saskatchewan River is a glacier-fed river that flows from the Canadian Rockies continental divide east to central Saskatchewan, where it joins with the South Saskatchewan River to make up the Saskatchewan River. Its water flows eventually into the Hudson Bay. The Saskatchewan River system is the largest shared between the Canadian provinces of Alberta and Saskatchewan. Its watershed includes most of southern and central Alberta and Saskatchewan. Course The North Saskatchewan River has a length of , and a drainage area of . At its end point at Saskatchewan River Forks it has a mean discharge of . The yearly discharge at the Alberta–Saskatchewan border is more than . The river begins above at the toe of the Saskatchewan Glacier in the Columbia Icefield, and flows southeast through Banff National Park alongside the Icefields Parkway. At the junction of the David Thompson Highway (Highway 11), it initially turns northeast for before switching to a more direct easter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overfishing
Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in the species becoming increasingly underpopulated in that area. Overfishing can occur in water bodies of any sizes, such as ponds, wetlands, rivers, lakes or oceans, and can result in resource depletion, reduced biological growth rates and low biomass levels. Sustained overfishing can lead to critical depensation, where the fish population is no longer able to sustain itself. Some forms of overfishing, such as the overfishing of sharks, has led to the upset of entire marine ecosystems. Types of overfishing include: growth overfishing, recruitment overfishing, ecosystem overfishing. The ability of a fishery to recover from overfishing depends on whether its overall carrying capacity and the variety of ecological conditions are suitable f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steamboat
A steamboat is a boat that is marine propulsion, propelled primarily by marine steam engine, steam power, typically driving propellers or Paddle steamer, paddlewheels. Steamboats sometimes use the ship prefix, prefix designation SS, S.S. or S/S (for 'Screw Steamer') or PS (for 'Paddle Steamer'); however, these designations are most often used for steamships. The term ''steamboat'' is used to refer to smaller, insular, steam-powered boats working on lakes and rivers, particularly riverboats. As using steam became more reliable, steam power became applied to larger, ocean-going vessels. Background Limitations of the Newcomen steam engine Early steamboat designs used Newcomen atmospheric engine, Newcomen steam engines. These engines were large, heavy, and produced little power, which resulted in an unfavorable power-to-weight ratio. The Newcomen engine also produced a reciprocating or rocking motion because it was designed for pumping. The piston stroke was caused by a water jet i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isinglass
Isinglass () is a substance obtained from the dried swim bladders of fish. It is a form of collagen used mainly for the clarification or fining of some beer and wine. It can also be cooked into a paste for specialised gluing purposes. The English word origin is from the obsolete Dutch ''huizenblaas'' – ''huizen'' is a kind of sturgeon, and ''blaas'' is a bladder, or German ''Hausenblase'', meaning essentially the same. Although originally made exclusively from sturgeon, especially beluga, in 1795 an invention by William Murdoch facilitated a cheap substitute using cod. This was extensively used in Britain in place of Russian isinglass, and in the US hake was important. In modern British brewing all commercial isinglass products are blends of material from a limited range of tropical fish. The bladders, once removed from the fish, processed, and dried, are formed into various shapes for use. Foods and drinks Before the inexpensive production of gelatin and oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caviar
Caviar (also known as caviare; from fa, خاویار, khâvyâr, egg-bearing) is a food consisting of salt-cured roe of the family Acipenseridae. Caviar is considered a delicacy and is eaten as a garnish or a spread. Traditionally, the term caviar refers only to roe from wild sturgeon in the Caspian Sea and Black Sea ( Beluga, Ossetra and Sevruga caviars). The term caviar can also describe the roe of other species of sturgeon or other fish such as paddlefish, salmon, steelhead, trout, lumpfish, whitefish, or carp. The roe can be "fresh" (non-pasteurized) or pasteurized, with pasteurization reducing its culinary and economic value. Terminology According to the United Nations' Food and Agriculture Organization, roe from any fish not belonging to the Acipenseriformes order (including Acipenseridae, or sturgeon ''sensu stricto'', and Polyodontidae or paddlefish) are not caviar, but "substitutes of caviar." This position is also adopted by the Convention on Internation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NatureServe
NatureServe, Inc. is a non-profit organization based in Arlington County, Virginia, US, that provides proprietary wildlife conservation-related data, tools, and services to private and government clients, partner organizations, and the public. NatureServe reports being "headquartered in Arlington, Virginia, with regional offices in four U.S. locations and in Canada." In calendar year 2011 they reported having 86 employees, 6 volunteers, and 15 independent officers. History The Nature Conservancy reports that in 2000 it spun off its 85-center Natural Heritage Network "into a new independent organization, the Association for Biodiversity Information (later renamed NatureServe)." NatureServe reports that it was established in 1994 as the Association for Biodiversity Information. In 2001 the IRS approved a name change to NatureServe that was requested in 1999, while maintaining the organization's 501(c)(3) tax-exempt status granted in July 1995. NatureServe's website declares that it i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benthic Zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "the depths." Organisms living in this zone are called benthos and include microorganisms (e.g., bacteria and fungi) as well as larger invertebrates, such as crustaceans and polychaetes. Organisms here generally live in close relationship with the substrate and many are permanently attached to the bottom. The benthic boundary layer, which includes the bottom layer of water and the uppermost layer of sediment directly influenced by the overlying water, is an integral part of the benthic zone, as it greatly influences the biological activity that takes place there. Examples of contact soil layers include sand bottoms, rocky outcrops, coral, and bay mud. Description Oceans The benthic region of the ocean begins at the shore line ( intert ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phototactic
Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis. Phototaxis is called positive if the movement is in the direction of increasing light intensity and negative if the direction is opposite. Two types of positive phototaxis are observed in prokaryotes. The first is called scotophobotaxis (from the word "scotophobia"), which is observed only under a microscope. This occurs when a bacterium swims by chance out of the area illuminated by the microscope. Entering darkness signals the cell to reverse flagella rotation direction and reenter the light. The second type of phototaxis is true phototaxis, which is a directed movement up a gradient to an increasing amount of light. This is analogous to positive chemotaxis except that the attractant is light rather than a chemic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelagic Zone
The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth (as illustrated on the right). The word ''pelagic'' is derived . The pelagic zone can be thought of as an imaginary cylinder or water column between the surface of the sea and the bottom. Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients (such as iron, magnesium and calcium) all change. Marine life is affected by bathymetry (underwater topography) such as the seafloor, shoreline, or a submarine seamount, as well as by proximity to the boundary between the ocean and the atmosphere at the ocean surface, which brings light for photosynthesis, predation from above, and wind stirring up waves and setting currents in motion. The pelagic zone refers to the open, free waters away from the shore, where marine life can swim freely in any direction unhindered by topographical constraints. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glacial Lake Iroquois
Glacial Lake Iroquois was a prehistoric proglacial lake that existed at the end of the last ice age approximately 13,000 years ago. The lake was essentially an enlargement of the present Lake Ontario that formed because the St. Lawrence River downstream from the lake was blocked by the ice sheet near the present Thousand Islands. The level of the lake was approximately 30 m (~100 ft) above the present level of Lake Ontario. The work of Anderson and Lewis (1985) is the basis for these authors' views on the history of the postglacial water levels. The lake drained to the southeast, through a channel passing near present day Rome, New York. The Rome Sand Plains has several sand ridges that geologists think were formed at this time. The channel then followed the valley of the Mohawk River to the Hudson River. The lake was fed by Early Lake Erie, as well as Glacial Lake Algonquin, an early partial manifestation of Lake Huron, that drained directly to Lake Iroquois across southe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Agassiz
Lake Agassiz was a large glacial lake in central North America. Fed by glacial meltwater at the end of the last glacial period, its area was larger than all of the modern Great Lakes combined. First postulated in 1823 by William H. Keating, it was named by Warren Upham in 1879 after Louis Agassiz, when Upham recognized that the lake was formed by glacial action. Geological progression During the last ice age, northern North America was covered by an ice sheet, which alternately advanced and retreated with variations in the climate. This continental ice sheet formed during the period now known as the Wisconsin glaciation, and covered much of central North America between 30,000 and 10,000 years ago. As the ice sheet disintegrated, its meltwaters created an immense proglacial lake. Around 13,000 years ago, this lake came to cover much of what are now southeastern Manitoba, northwestern Ontario, northern Minnesota, eastern North Dakota, and Saskatchewan. At its greatest exten ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
