There are few sub arctic areas all over the world that are biologically productive. The Bering Sea is one of them. It is one of the richest fishing grounds with inclement weather on our planet. Warm and calm seas are not very productive from the harvesting point of view and cannot support lucrative fisheries. On the contrary, the Bering, Barents, Greenland, Norwegian and Okhotsk seas are full of fish. They all are transitional regions, influenced by both the Arctic and either the North Pacific or Atlantic Oceans respectively; and to a greater or lesser extent, they share some properties with the arctic waters to the north.
The Bering Sea itself is under control of atmospheric and oceanic processes in the Arctic Ocean to the north, where they are linked by the Bering straits waters, and the North Pacific Ocean to the south. Properties and characteristics of both oceans merge in The Bering Sea and Bering Straits waters, creating a unique blend of polar and north temperate features. The Bering Sea is the world's third-largest semi-enclosed sea. Almost half of its total area is extremely shallow, in many places the deepness is less than sixty meters. Nevertheless, the rest of the basin is deep, exceeding three thousand meters.
The Bering Sea's biological regimes are often described as "teaming", the "richest", "most productive" and so on. Indeed, for years the sea proves its status of being extraordinarily productive, especially at the so-called higher tropic levels. It is inhabited by large populations of birds, mammals and fish. Since the early days human beings have continuously harvested the impressive biological wealth of the region. It includes Pacific cod, sea otters, fur seals, whales, crabs, salmon and, most recently, Pollock. Walrus and beluga whales are also important subsistence species in the northern Bering Sea. Today, the Bering Sea Pollock fishery is the largest single species fishery in the world, providing a substantial proportion of the annual fish catch of the United States.
There are several reasons for the Bering straits and Bering Sea waters to be so rich in numbers of species at multiple tropic levels. First of all, the biological wealth is influenced and to some extend a consequence of juxtaposition of the Bering Sea. What is more, there is a correlation of ocean conditions, which evidently experience the Bering Sea climate change, and the high marine biodiversity and productivity.
Nutrient-rich water enters the Bering Sea through the passes from the Gulf of Alaska onto the outer eastern continental shelf and Bering Straits waters. Its nitrogenous nutrient content is sufficiently high to preclude the exhaustion, as the water passes through the Bering Sea. Such nutrition from the northward movement leads to a high productivity of plant growth over the shelf of the sea. Another explanation of multiple species, existing in the sea, is an outcome of undersea canyons, which run up into the shelf from the deep basin. Such hydrographic regime makes up a belt of high productivity in summer along the outer edge of the shelf, the so-called "Green Belt".