Muscular system is a set of muscles capable of contracting and performing mechanical work. Depending on the structure of muscle cells, there are transverse striated muscles, which form the entire skeletal musculature, and smooth muscles, which form the musculature of internal organs. The exception is the heart muscle, formed by transverse striated muscle tissue of a special structure. Muscles of the body of fish are divided into muscles of the trunk, tail, head and fins. Each species of fish has its own muscle color. Thus, pikeperch has a white muscle color, sturgeon - yellowish, trout - pink, nerka - red. However, muscle color is to some extent influenced by the composition of food and water.