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Hydrocynus Forskahlii
''Hydrocynus forskahlii'', the elongate tigerfish, is a species of predatory characin from the family Alestidae which is found in northern and western Africa. Description ''Hydrocynus forskahlii'' has pronounced stripes along the length of the body. There are two scales between the pelvic fin insertion and the lateral line, less than for other species of tigerfish such as ''Hydrocynus brevis'' which has 23-5 scales in the same position. The lateral line scale count is between 46 and 53 scales and the anal fin ray count is 3 soft, unbranched rays with 11-14 branched rays. It is a slenderer species than other Hydrocynus and the depth of the body averages 22.6 per cent of its length and the head averages around 20 per cent of the body length. It has 9 to 14 teeth in the upper jaw and 8 to 12 in the lower jaw and the jaws are frequently short and upturned. They are similar in colour and pattern to ''Hydrocynus vittatus'' being bright, silvery white in color, but with a grayish tail tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Georges Cuvier
Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuvier was a major figure in natural sciences research in the early 19th century and was instrumental in establishing the fields of comparative anatomy and paleontology through his work in comparing living animals with fossils. Cuvier's work is considered the foundation of vertebrate paleontology, and he expanded Linnaean taxonomy by grouping classes into phylum, phyla and incorporating both fossils and living species into the classification. Cuvier is also known for establishing extinction as a fact—at the time, extinction was considered by many of Cuvier's contemporaries to be merely controversial speculation. In his ''Essay on the Theory of the Earth'' (1813) Cuvier proposed that now-extinct species had been wiped out by periodic catastrophi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Gambia
The Gambia River (formerly known as the River Gambra) is a major river in West Africa, running from the Fouta Djallon plateau in north Guinea westward through Senegal and The Gambia to the Atlantic Ocean at the city of Banjul. It is navigable for about half that length. The river is strongly associated with The Gambia, the smallest country in mainland Africa, which occupies the downstream half of the river and its two banks. Geography The Gambia River runs a total length of . From the Fouta Djallon, it runs northwest into the Tambacounda Region of Senegal, where it flows through the Parc National du Niokolo Koba, then is joined by the Nieri Ko and and passing through the Barrakunda Falls before entering the Gambia at Koina. At this point, the river runs generally west, but in a meandering course with a number of oxbows, and about from its mouth it gradually widens, to over wide where it meets the sea. Crossings There are several bridges crossing the river. The largest an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alestes Baremoze
''Alestes baremoze'', the pebbly fish or silversides, is a species of characin fish from the freshwater systems of northern and western Africa. It has some importance as a commercially exploited food fish. Description ''Alestes baremoze'' is a silver-coloured fish with a bluish-grey dorsum and a white belly, the fins are greyish with an orange coloured lower lobe of the caudal fin. The maximum published length is 43 cm and the maximum published weight is 500g, although sexual maturity is reached at about 20 cm. It belongs to order Characiformes, family Alestidae, and genus ''Alestes''. Histomorphological observations and stomach content analysis suggested that ''A. baremoze'' has morphological adaptations for omnivory Distribution In eastern Africa it is found within Lake Albert, the White Nile and Lake Turkana. In Northern Africa ''Alestes baremoze'' was formerly distributed along the whole of the River Nile in Egypt, including the Nile Delta lakes, Rosetta Branch and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Characin
Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationships of the Characidiinae and phylogeny of characiform fishes (Teleostei: Ostariophysi)", ''Phylogeny and Classification of Neotropical Fishes'', L.R. Malabarba, R.E. Reis, R.P. Vari, Z.M. Lucena, eds. (Porto Alegre: Edipucr) 1998:123-144. Taxonomy The Characiformes form part of a series called the Otophysi within the superorder Ostariophysi. The Otophysi contain three other orders, Cypriniformes, Siluriformes, and Gymnotiformes. The Characiformes form a group known as the Characiphysi with the Siluriformes and Gymnotiformes. The order Characiformes is the sister group to the orders Siluriformes and Gymnotiformes, though this has been debated in light of recent molecular evidence. Originally, the characins were all grouped within a single ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clupeidae
Clupeidae is a family of ray-finned fishes, comprising, for instance, the herrings, shads, sardines, hilsa, and menhadens. The clupeoids include many of the most important food fishes in the world, and are also commonly caught for production of fish oil and fish meal. Many members of the family have a body protected with shiny cycloid (very smooth and uniform) scales, a single dorsal fin, and a fusiform body for quick, evasive swimming and pursuit of prey composed of small planktonic animals. Due to their small size and position in the lower trophic level of many marine food webs, the levels of methylmercury they bioaccumulate are very low, reducing the risk of mercury poisoning when consumed. Description and biology Clupeids are mostly marine forage fish, although a few species are found in fresh water. No species has scales on the head, and some are entirely scaleless. The lateral line is short or absent, and the teeth are unusually small where they are present at all. Clupe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nigeria
Nigeria ( ), , ig, Naìjíríyà, yo, Nàìjíríà, pcm, Naijá , ff, Naajeeriya, kcg, Naijeriya officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea to the south in the Atlantic Ocean. It covers an area of , and with a population of over 225 million, it is the most populous country in Africa, and the world's sixth-most populous country. Nigeria borders Niger in the north, Chad in the northeast, Cameroon in the east, and Benin in the west. Nigeria is a federal republic comprising of 36 states and the Federal Capital Territory, where the capital, Abuja, is located. The largest city in Nigeria is Lagos, one of the largest metropolitan areas in the world and the second-largest in Africa. Nigeria has been home to several indigenous pre-colonial states and kingdoms since the second millennium BC, with the Nok civilization in the 15th century BC, marking the first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Kainji
Kainji Lake, in North Central Nigeria, is a reservoir on the Niger River, formed by the Kainji Dam. It was formed in 1968 and is a part of Niger State and Kebbi State. Kainji Lake National Park (KNLP), situated around the lake, is Nigeria's oldest National Park, established in 1976. Kanji Dam The Kainji Dam is situated in Northern Niger State and generates power for most towns in Nigeria. It was built from 1964 to 1968 and cost about 209 million dollars, a quarter of which was used to relocate the original population. Together with a smaller dam for a minor stream, it is long and high in the middle. It has a capacity of 12 turbines producing a total of 960 MW, but only 8 were installed, producing 760 MW. Part of the production is sold to the neighbouring country of Niger. National Park Kainji Lake National Park (KNLP) (headquarters Wawa) is situated north of Lagos, close to the border with the Republic of Benin. It comprises two sectors, Borgu Game Reserve and Zugurma Game ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepsetus Odoe
''Hepsetus odoe'', the African pike characin, is a predatory freshwater characin belonging to the family Hepsetidae. It was formerly considered that there was a single species of ''Hepsetus'' pike characin but recent studies have led to the species being split and ''Hepsetus odoe'' ''sensu stricto'' is the west African representative of the group. Description It is an elongated fish with a pike-like body, however this species is a characin and the pike resemblance is due to convergent evolution. This species can reach up to about in length. The back is normally dark brown or green while the belly is silver. The head is normally light green or brown with distinct dark brown or black stripes radiating out from the eye. The colour and pattern of adult fish is relatively stable but juveniles are more variable. Distribution ''Hepsetus odoe'' is found in western sub-Saharan Africa, from the Sassandra River in the Cote d'Ivoire in the west to the Shari River in the Central African Rep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Kariba
Lake Kariba is the world's largest artificial lake and reservoir (water), reservoir by List of lakes by volume, volume. It lies upstream from the Indian Ocean, along the border between Zambia and Zimbabwe. Lake Kariba was filled between 1958 and 1963 following the completion of the Kariba Dam at its northeastern end, flooding the Kariba Gorge on the Zambezi River. The Zimbabwean town of Kariba, Zimbabwe, Kariba was built for construction workers on the lake's dam, while some other settlements such as Binga village and Mlibizi in Zimbabwe and Siavonga and Sinazongwe in Zambia have grown up to house people displaced by the rising waters. Physical characteristics Lake Kariba is over long and up to in width. It covers an area of and its storage capacity is . The mean depth of the lake is ; the maximum depth is . It is the world's largest man-made reservoir by volume, four times as large as the Three Gorges Dam. The enormous mass of water (approximately 180,000,000,000,000 kilogra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potamodromous
Fish migration is animal migration, mass relocation by fish from one area or body of water to another. Many types of fish migrate on a regular basis, on time scales ranging from daily to annually or longer, and over distances ranging from a few metres to thousands of kilometres. Such migrations are usually done for better feeding or to reproduce, but in other cases the reasons are unclear. Fish migrations involve movements of school of fish, schools of fish on a scale and duration larger than those arising during normal daily activities. Some particular types of migration are ''anadromous'', in which adult fish live in the sea and migrate into fresh water to spawn (biology), spawn; and ''catadromous'', in which adult fish live in fresh water and migrate into salt water to spawn. Marine forage fish often make large migrations between their spawning, feeding and nursery grounds. Movements are associated with ocean currents and with the availability of food in different areas at di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelagic
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] |
Sympatry
In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sharing a common range exemplifies sympatric speciation. Such speciation may be a product of reproductive isolation – which prevents hybrid offspring from being viable or able to reproduce, thereby reducing gene flow – that results in genetic divergence. Sympatric speciation may, but need not, arise through secondary contact, which refers to speciation or divergence in allopatry followed by range expansions leading to an area of sympatry. Sympatric species or taxa in secondary contact may or may not interbreed. Types of populations Four main types of population pairs exist in nature. Sympatric populations (or species) contrast with parapatric populations, which contact one another in adjacent but not shared ranges and do not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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