O.V. Titov, Yu.M. Lepesevich, N.A. Tarasov, A.P. Pedchenko
Polar Research Institute of Marine Fisheries and Oceanography (PINRO),
Murmansk, Russia

The ecosystem of the Barents Sea is at the border between warm Atlantic and cold Arctic waters, i.e. in the area of interaction of two oceanic systems.

Such a geographical location of sea is extensively determined by the climatic peculiarities of the basin, the area of the ice coverage and its boundaries, as well as the presence extended frontal zones. To opinion of some scientists (Knipovich, 1938; Zenkevich, 1963 et al.), just because of the interaction of Arctic and boreal waters the Barents Sea ecosystem has a high level of biological productivity and is rich in commercial bioresources (about 5 % of the whole world yield of the sea and oceanic fishes).

The last decade is in general characterized by the stable increase of the air temperature over the area of the Barents Sea and adjacent seas. The similar processes were observed in the hydrosphere that is proved by the anomaly high water temperatures of the Barents Sea registered in the Kola section in 2000-2006.

The global warming up in the system "ocean-atmosphere" caused the decrease of the ice cover area in the sea.

However, the similar climatic situation has been registered before. The previous period of warming up of the Arctic was observed since the end of the XIXth century to the 1960's and affected the most of areas of the North Atlantic from the shores of Greenland to the Kara Sea. This process entailed the penetration into the Arctic waters of many heat-loving species not observed there before, as well as escapement of the typical inhabitants of the cold seas, changing of qualitative and quantitative composition of complexes, and shift of fishing grounds into the northern and eastern direction (Zenkevich, 1963). Nearby the western coast of the Spitsbergen archipelago the activation of the fishing for cod and haddock was observed; off the Novaya Zemlya shores the herring, mackerel, haddock and saithe species began to appear. The suppositions have arisen on the possible spawning of cod and saithe off the Novaya Zemlya coast. The species observed in the White Sea were haddock, saithe and red-fishes, whereas in the Kara Sea - Atlantic herring and cod (Zenkevich, 1963).

It should be mentioned that the duration of the present warm period is less than the previous one, and the values of the climate index in the early of the XXIst are lower than its extreme values in 1930-1950. Long-term predictions carried out by PINRO do not give the basis to speak on the retention of a tendency to warming up in the nearest future. Nevertheless, even today there is a unique possibility to explore the happening changes in the Barents Sea ecosystem and in the adjacent areas and to prepare the probable scenarios of the climatic changes influence on the fishery.

The present-day changes of climate have already an impact on the biological resources of the Barents Sea and adjacent areas. The most noticeable changes take place in the geographical re-distribution of the fishing objects over the sea and in revealing of new fish species traditionally dwelling in warm Atlantic waters (Rusyaev and Shatsky, 2001; Smirnov et al., 2000; Pedchenko et al., 2006; Dolgov, 2004; Lepesevich, 1999; Anon., 2004). The acclimatization and widening of the red king crab habitat are more active against the background of the climate warming up.

Increase of the warm waters transference into the Barents Sea and decrease of the Barents Sea ice coverage are the reasons of the growth of the total biological productivity (by our estimates, the increase of production of phytoplankton in the Barents Sea in 2006 could constitute about 20 % of the long-term mean). This is a favorable prerequisite for higher survival of young boreal fishes, increase in the future of their stocks and areas and, finally, for a tendency to increase of the fisheries productivity of the Barents Sea.

The process of the sea warming up can have far-reaching implications not only for heat-loving species.lt is known that Sebastes mentella and Greenland halibut larvae adapted themselves to spend a part of life under sever temperature conditions at high latitudes of the Arctic, where the influence of predators is insufficient, and they have an advantage in survival over typically boreal species because of the low elimination (Anon., 2004). Since the middle of the 1990's the penetration of blue whiting into the Barents Sea has been registered. This fact, as well as shifting to the north of cod spawning grounds, can change the situation and influence both on the recruitment value of many commercial fish species and the abundance of traditional objects of feeding of the other predators: capelin and polar cod.

The recent years investigations of PINRO (Titov et al., 2006) show that the frontal zones of the Barents Sea have a great impact on both the distribution and abundance of commercial fishes. The consequence of changing of cycling of climatic processes in the last decade is the fact that at the background of climate warming up the contracts between the Arctic and Atlantic oceanic systems became weaker, and the frontal zones in the Barents Sea became correspondingly fuzzier. This was fixed with the use of calculated parameters based on observations of PINRO expeditions. In connection with that one can assume that the climate warming up could have a certain negative impact on the abundance of such important commercial species as cod and capelin, the habitats of which are densely connected with frontal zones.

Thus, even now it is necessary to switch the task of studying of implications of the climate change from theory to practice. To our opinion one of the first steps in investigations of implications of the global warming up for the fishing bioresources can be a program of studying of fishing bioresources in the Kara Sea. Stable climatic changes can lead to the reconstruction of ecosystems of the Barents, White and Kara Seas, to changes in migration and distribution of fishing objects or to the appearance in the nearest future of independent self-reproductive population. It is relevant also to explore the dependence and interrelation between components of stocks in the Barents and Kara Seas. The absence of these data can lead to stock underestimation of fishing objects in traditional areas of their distribution, where the standard surveys are carried out.

FISHERY IN NORTH ATLANTIC: REALITY AND PROSPECTS