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Sommen Charr
The Sommen charr ( sv, Sommenröding) is a population or subspecies of Arctic charr found in Lake Sommen. It is one of twenty-two species of fish found in the lake. This population and other Arctic charrs in southern Sweden are regarded as relict populations at the southern edge of the natural distribution of Arctic charrs. Survival of Arctic charrs at the southern edge of their natural range is explained by Lake Sommens having a great depth () with cold and oxygen-rich bottom waters. Sommen charr may also draw benefits from the lake's richness in fish species and the complex ecology it implies. Populations of Sommen charr declined over the 20th century, leading to the fish being declared endangered in 1970. The causes of the decline are likely to include overfishing, fishing of immature individuals, unnatural lake level changes (as the lake is regulated), and competition from introduced species. The largest known Sommen charr weighed almost , and was for a while the largest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salvelinus Alpinus - Lake Inari Population
''Salvelinus'' is a genus of Salmonidae, salmonid fish often called char or charr; some species are called "trout". ''Salvelinus'' is a member of the subfamily Salmoninae within the family Salmonidae. The genus has a northern circumpolar distribution, and most of its members are typically cold-water fish that primarily inhabit fresh waters. Many species also migrate to the sea. Most char may be identified by light-cream, pink, or red spots over a darker body. Scales tend to be small, with 115-200 along the lateral line. The pectoral, pelvic, anal, and the lower aspect of caudal fins are trimmed in snow white or cream leading edges. Many members of this genus are popular sport fish, and a few, such as lake trout (''S. namaycush'') and arctic char (''S. alpinus'') are objects of commercial fisheries and/or aquaculture. Occasionally, such fish escape and become invasive species. Deepwater char are small species of char living below 80 m in the deep areas of certain lakes. They are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northern Pike
The northern pike (''Esox lucius'') is a species of carnivorous fish of the genus '' Esox'' (the pikes). They are typical of brackish and fresh waters of the Northern Hemisphere (''i.e.'' holarctic in distribution). They are known simply as a pike in Britain, Ireland, and most of Eastern Europe, Canada and the United States. Pike can grow to a relatively large size: the average length is about , with maximum recorded lengths of up to and published weights of . The IGFA currently recognizes a pike caught by Lothar Louis on Greffern Lake, Germany, on 16 October 1986, as the all-tackle world-record northern pike. Northern pike grow to larger sizes in Eurasia than in North America, and typically grow to larger sizes in coastal than inland regions of Eurasia. Etymology The northern pike gets its common name from its resemblance to the pole-weapon known as the pike (from the Middle English for 'pointed'). Various other unofficial trivial names are common pike, Lakes pike, great n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural Selection
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Charles Darwin popularised the term "natural selection", contrasting it with selective breeding, artificial selection, which in his view is intentional, whereas natural selection is not. Genetic diversity, Variation exists within all populations of organisms. This occurs partly because random mutations arise in the genome of an individual organism, and their offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits. The environment of a genome includes the molecular biology in the Cell (biology), cell, other cells, other individuals, populations, species, as well as the abiotic environment. Because individuals with certain variants of the trait tend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Flow
In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish Biology
Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of living fish species are ray-finned fish, belonging to the class Actinopterygii, with around 99% of those being teleosts. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a vertebrate, true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed placodermi, external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Ladoga
Lake Ladoga (; rus, Ла́дожское о́зеро, r=Ladozhskoye ozero, p=ˈladəʂskəjə ˈozʲɪrə or rus, Ла́дога, r=Ladoga, p=ˈladəɡə, fi, Laatokka arlier in Finnish ''Nevajärvi'' ; vep, Ladog, Ladoganjärv) is a freshwater lake located in the Republic of Karelia and Leningrad Oblast in northwestern Russia, in the vicinity of Saint Petersburg. It is the largest lake located entirely in Europe, the second largest lake after Baikal in Russia, and the 14th largest freshwater lake by area in the world. ''Ladoga Lacus'', a methane lake on Saturn's moon Titan, is named after the lake. Etymology In one of Nestor's chronicles from the 12th century a lake called "the Great Nevo" is mentioned, a clear link to the Neva River and possibly further to Finnish ''nevo'' 'sea' or ''neva'' 'bog, quagmire'. Evgeny Pospelov: ''Geographical names of the world. Toponymic dictionary.'' Second edition. Astrel, Moscow 2001, pp. 106f. Ancient Norse sagas and Hanseatic tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA is only a small portion of the DNA in a eukaryotic cell; most of the DNA can be found in the cell nucleus and, in plants and algae, also in plastids such as chloroplasts. Human mitochondrial DNA was the first significant part of the human genome to be sequenced. This sequencing revealed that the human mtDNA includes 16,569 base pairs and encodes 13 proteins. Since animal mtDNA evolves faster than nuclear genetic markers, it represents a mainstay of phylogenetics and evolutionary biology. It also permits an examination of the relatedness of populations, and so has become important in anthropology and biogeography. Origin Nuclear and mitochondrial DNA are thought to be of separate evolutionary origin, with the mtDNA being derived ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deglaciation
Deglaciation is the transition from full glacial conditions during ice ages, to warm interglacials, characterized by global warming and sea level rise due to change in continental ice volume. Thus, it refers to the retreat of a glacier, an ice sheet or frozen surface layer, and the resulting exposure of the Earth's surface. The decline of the cryosphere due to ablation can occur on any scale from global to localized to a particular glacier. After the Last Glacial Maximum (ca. 21,000 years ago), the last deglaciation begun, which lasted until the early Holocene. Around much of Earth, deglaciation during the last 100 years has been accelerating as a result of climate change, partly brought on by anthropogenic changes to greenhouse gases. The previous deglaciation took place from approximately 22 ka until 11.5 ka. This occurred when there was an annual mean atmospheric temperature on the earth that increased by roughly 5 °C, which was also accompanied by regional hi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salvelinus Umbla
''Salvelinus umbla'', also known as lake char, is a species of char found in certain lakes of the region of the Alps in Europe. This char species usually inhabits the deeper waters of the lakes, feeding on crustaceans, insects and benthic fauna. Larger specimens can be piscivores. They look for areas with pebbly or stony bottom on steep slopes, at depths between 30 and 120 m during the spawning season. Distribution This char species lives in alpine and subalpine glacial valley lakes of central Europe, between France and Austria and between Germany and Northern Italy. It has been introduced in high altitude lakes as well. Although it is assessed as a least concern species by IUCN, the eutrophication of the lakes in the Subalpine region, which began in the 1950s and peaked in 1979, badly affected ''Salvelinus umbla'' populations, which crashed during that period. The lake char became locally extinct in lakes such as Mondsee and other char species, such as ''Salvelinus profund ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salvelinus Lepechini
''Salvelinus'' is a genus of Salmonidae, salmonid fish often called char or charr; some species are called "trout". ''Salvelinus'' is a member of the subfamily Salmoninae within the family Salmonidae. The genus has a northern circumpolar distribution, and most of its members are typically cold-water fish that primarily inhabit fresh waters. Many species also migrate to the sea. Most char may be identified by light-cream, pink, or red spots over a darker body. Scales tend to be small, with 115-200 along the lateral line. The pectoral, pelvic, anal, and the lower aspect of caudal fins are trimmed in snow white or cream leading edges. Many members of this genus are popular sport fish, and a few, such as lake trout (''S. namaycush'') and arctic char (''S. alpinus'') are objects of commercial fisheries and/or aquaculture. Occasionally, such fish escape and become invasive species. Deepwater char are small species of char living below 80 m in the deep areas of certain lakes. They are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Northwestern Russia
Northwest Russia, or the Russian North is the northern part of western Russia. It is bounded by Norway, Finland, the Arctic Ocean, the Ural Mountains and the east-flowing part of the Volga. The area is roughly coterminous with the Northwestern Federal District, which it is administered as part of. Historically, it was the area of the Novgorod and Pskov merchant republics. Although the Northwest was never a political unit there is some reason for treating it as a distinct region. The Volga marks the approximate northern limit of moderately dense settlement. The area to the north was valued mainly as a source of fur. The western side was the main source of squirrel, for which there was a large demand during the Middle Ages. Luxury fur, especially sable, came mostly from the northeast. Last glacial period The Weichselian glaciation that came to cover much of northwestern originated most likely from small ice fields and ice caps in the Scandinavian Mountains before the ice spread ea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Piscivory
A piscivore () is a carnivorous animal that eats primarily fish. The name ''piscivore'' is derived . Piscivore is equivalent to the Greek-derived word ichthyophage, both of which mean "fish eater". Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted reptiles and synapsids evolved herbivory. Almost all predatory fishes (most sharks, tuna, billfishes, pikes etc.) are obligated piscivores. Some non-piscine aquatic animals, such as whales, sea lion and crocodilians, are not completely piscivorous, often also preying on invertebrates, marine mammals, waterbirds and even wading land animals in addition to fish; while others, such as the bulldog bat and gharial, are strictly dependent on fish for food. Some creatures, including cnidarians, octopuses, squid, spiders, cetaceans, grizzly bears, jaguars, wolves, snakes, turtles and sea gulls, may have fish as significa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
