Fish spawn on a variety of substratesMost marine fish eggs are just spawned into the water column (horse mackerel, anchovy, sprat, Red mullet, tuna and many others) and pay no attention on their offsprings. these eggs are positively buoyant and develop in the upper layer of the sea. Many marine and freshwater fish species lay eggs on aquatic vegetation (herring, needlefish, carp) or on the bottom of the reservoir (sturgeon). Salmon leave the sea to spawn in the river, dig the eggs in the pebbled bottom, lay their eggs in them, and then bury its eggs by pebbles by the powerful movements of the tail. Little Jumping Characin lays eggs on the leaves of plants, hanging over the water. To do this, males and females have both repeatedly jump out of the water.Read more

Scientists assume that the life on our planet originated from water. All ancestors of the fishes were aquatic organisms, and they never went ashore in the process of evolution. Read more

Evolution of fishes occurred over a long period of time. According the oldest known fossil remains, the fishes already lived in the early Cambrian, that is about 530 million years ago. Ancient fish slightly resembled the modern one. The shell-skinned Ostracoderms that lived in the Ordovic period had neither air bladder, nor skeleton, as scientists suggest, and were very clumsy while swimming. In the Silurian there were already a lot of Armoured fishes, from them descended Placoderms, from them - the ancestors of Acanthodii, sometimes called spiny sharks, Lat. Acanthodii) and Cartilaginous fishes ( Lat. Chondrichthyes). In the Silurian fish first appeared jaws and teeth.Read more

Each species of living organisms evolutionarily was adapted to specific habitats, and has its own type of water-salt metabolism - a set of processes of absorption, distribution, consumption and allocation of water and salts in the body.

Deep seas are inhabited by very small number of fishes. At present only 7 species of fish: three species of cusk eels (Ophidiidae) and four species of snailfishes (Liparidae) were found in the deep trenches. The deepest caught fishes were Abyssobrotula caught in the Puerto Rico Trench at the depth 8370 m and Hadal snailfish Pseudoliparis amblystomopsis caught at 7800 meters depth. Startling is the appearance of the deep-sea fishes: most of them have slim, jelly-like body, which are luminous bodies.Read more