Fish (lat. Pisces) - a group (in accordance with modern principles of cladistics - a paraphyletic group) of aquatic vertebrates. An extensive group of jawed mouths, which are characterized by gill breathing at all stages of the postembryonic development of the organism. Fish live in both salt and fresh water, from deep ocean trenches to mountain streams. Fish play an important role in most aquatic ecosystems as part of the food chain. They are of great economic importance to humans due to their consumption.
The size of modern fish varies from 7.9 mm (Paedocypris progenetica) to 20 m (whale shark).
There are (as of August 5, 2013) 32,834 species of fish known in the world. Every year, about 300-500 species new to science are described. About 3,000 species live in Russia, including more than 280 species found in fresh waters.
Origin and evolution of fish
It was believed that the most ancient jawless animals, resembling fish, are known from the early Ordovician (about 450-470 million years ago). However, in 1999, in the Chinese province of Yunnan, fossils of the fish-like creature Haikouichthys from the jawless group about 530 million years old (Early Cambrian) were found. Perhaps similar forms were the ancestors of all vertebrates.
Fossils of the lobe-finned fish Osteolepis macrolepidotus from the middle Devonian period (Great Britain)
The difference between the first fish and the jawless ones was the jaw, a derivative of one of the gill arches. In addition to jaws, fish have paired fins, an inner ear with three semicircular canals, and gill arches. Despite the appearance of the first jawed fish as early as the Ordovician, they occupied a subordinate position until the Devonian. Thus, fish and agnathans existed for more than 100 million years under the predominance of agnathans, in contrast to the present. Cartilaginous fish appeared at the turn of the Silurian and Devonian, about 420 million years ago, and reached their peak in the Carboniferous. Lobe-finned fish have lived in the world's oceans since at least the Devonian; it is possible that they already existed in the Silurian. Guiyu oneiros is the earliest known lobe-finned fish.
White shark off the coast of the island of Guadelupe (Mexico)
More than half of all living vertebrate species, namely, according to the FishBase database, about 31 thousand species, belong to fish. The number of recognized species continues to change due to the discovery of new species, as well as taxonomic revisions of individual groups. Living fish are represented by three classes: cartilaginous fish (Chondrichthyes), lobe-finned fish (Sarcopterygii) and ray-finned fish (Actinopterygii). The last two classes make up the bony fish group.
Modern cartilaginous fish are divided into two subclasses - Holocephali (whole-headed) and Elasmobranchii (plate-branched, which includes sharks and rays). Now there are 900-1000 species of cartilaginous fish.
What is the healthiest fish for humans? This question is difficult to answer unequivocally, since many fish have all the necessary saturated and unsaturated fatty acids, trace elements, minerals and vitamins. The difference lies in the fact that some representatives contain less nutrients in themselves, while others contain more. From more than 20 thousand species of inhabitants of the water expanses, we have selected the most useful types of fish for human health.
Pike
Pike discovers the ten most useful fish species for humans. This is the only non-marine representative that was able to get into our rating. According to the content of vitamins, microelements, minerals and fatty acids, pike is in no way inferior to marine life. The fish is completely absent of carbohydrates and contains easily digestible proteins. Eating pike several times a week contributes to longevity, increased intelligence and the prevention of cardiovascular disease.
Tuna
Tuna is one of the most useful fish for humans. The marine product has a whole range of useful and nutritious substances: retinol acetate (A), thiamine (B), riboflavin (B2), niacin (B3), choline (B4), B12, E, folic acid, copper, iron, potassium - this is just a small list of all the useful substances in tuna. Useful microelements and substances of this fish take part in the metabolic processes of the body, have an anti-inflammatory effect, and with regular use increase endurance, physical and mental abilities. Regular intake of tuna, like any other fish, contributes to longevity.
Herring
Herring is not only one of the cheapest types of fish, but also very useful. Atlantic Ocean Dweller is rich in DHA and EPA acids, which boost the immune system, detoxify and improve eyesight. In addition, herring contains substances that have anti-inflammatory and regenerating effects. The product is useful for hypertensive patients, as it is able to normalize blood pressure, but it should be consumed only in lightly salted form. In addition, herring is recommended for diabetics and people with high cholesterol. Fish is considered an indispensable source of easily digestible protein.
Sardine
The sardine has also been awarded the status of the healthiest fish for human health. It is a source of trace elements, minerals and contains all the necessary vitamins: PP, B2, B12, D and others. Cod has anti-inflammatory properties and is helpful in treating arthritis and other joint related conditions. Regular intake of this type of food allows you to lower cholesterol and maintain it in normal range. Sardine reduces the risk of malignant tumors, strengthens the nervous system, memory, improves metabolism. In addition, fish is considered a natural antidepressant.
Rainbow trout
Rainbow trout is very healthy for humans due to its high content of easily digestible protein and low calorie content. The animal product is replete with both fat-soluble and water-soluble vitamins. Among the trace elements present in fish, potassium, magnesium, iron, selenium, zinc, and phosphorus should be distinguished. Eating trout at least once a week reduces the risk of high cholesterol and the formation of cholesterol plaques on the vessels, and helps strengthen the nervous system and memory.
Halibut
The list of the most useful fish for humans includes halibut. The species of the flounder family is not only a source of fatty amino acids, but also a storehouse of trace elements and minerals. Potassium, phosphorus, sodium, selenium, magnesium, iron - this is just a small list of what the product is rich in. Fans of this fish who eat it regularly are less likely to have vision problems, are less susceptible to cardiovascular diseases, and do not have problems with the gastrointestinal tract. The use of halibut cod is especially beneficial for health, which is several times superior to cod liver in terms of nutritional and beneficial properties.
Cod
Cod takes fourth place in the list of the most useful fish. The inhabitant of sea waters can also boast of useful substances and trace elements, as it is almost a whole vitamin complex. There is a lot of iodine in cod, which is vital for the normal functioning of the whole organism: it increases physical endurance and mental abilities. Vitamin PP normalizes the activity of the gastrointestinal tract, making the body work like a clock, and also helps to strengthen the nervous system. Sulfur, which is part of cod, has an antibacterial effect and improves the condition of hair, skin and nails. This species is very rich in omega acids.
Notothenia
The status of the most useful fish for a person deserves notation. The nutritional properties of notothenia are in no way inferior to meat, in addition, fish protein is absorbed better by the body than meat. Like all fish, it contains essential amino acids, which are contained in it in the required amount. In notothenia, all the necessary vitamins and minerals are present in abundance. Chromium allows you to better withstand stressful situations and fatigue. People who use notothenia up to 2-3 times a week are less prone to depression and chronic fatigue. Also, this fish is recommended for people with low hemoglobin: it contains cobalt, which stimulates the production of blood cells.
Mackerel
Mackerel or mackerel is one of the healthiest fish for human health. In 100 gr. The marine product contains half of the daily norm of the protein necessary for the body, which, moreover, is also easily digested. Regular consumption of mackerel helps to normalize blood cholesterol levels. Vitamin A, which is part of the fish, is responsible for tissue regeneration, phosphorus makes the skeletal system stronger. In addition, mackerel contains sulfur, which allows the body to fight harmful bacteria. Sodium maintains the water-salt balance in the cells of the body. Nicotinic acid is responsible for strengthening the nervous system.
1 Salmon
Salmon and all fish of the salmon family are the most beneficial for humans. Salmon include such species as salmon, pink salmon, chum salmon, trout, kizhich and others. The meat of these species is not only very tasty, but also the most useful. The protein contained in the marine product is easily absorbed by the body. Salmon more than other species are enriched with saturated and unsaturated fats, omega-3 and omega-6 fatty acids. In addition, they contain such important substances for the health of each person as vitamins of groups B and D. Vitamin D is responsible for the absorption of calcium in the body, and group B is responsible for the health of the skin, hair, proper functioning of the gastrointestinal tract, and also strengthens the nervous system. Salmon must be present in the diet of the elderly and athletes. It slows down the aging process in the body, accelerates regeneration processes and is an excellent preventive product against cardiovascular diseases.
