Water productivity is the amount of organic matter produced in a water body by its inhabitants per unit time (usually per year), per unit area of bed or per unit volume of water. Aquatic plants, which provide food for aquatic animals, form the basis of water productivity. In the coldest Arctic and Antarctic seas, water productivity is low and organisms develop slowly. In the temperate zone, the productivity of water bodies increases; in tropical seas, the speed of biological processes is greatest, but because the biomass of organisms is lower than in the temperate zone, the productivity of water bodies decreases somewhat.
The biological productivity of a water body is the ability of the water body to determine a particular character of substance development in living organisms and the rate of reproduction of that substance. A distinction is made between the general biological productivity and the commercial biological productivity of a water body. The commercial biological productivity of a water body is expressed as the number of fish caught per year in kilograms per hectare of water surface. Annual fish production of less than 30 kg ha is considered low, 30-60 kg ha is considered medium and more than 60 kg ha is considered high.