The main objective of the report is to give a comprehensive description of the Barents Sea ecosystem, including human activities and impact in the area, using relevant scientific and monitoring knowledge from Norwegian, Russian and other sources. ]]>
The surface sediments, i.e. the predominant sediment type of the upper ~ 50 cm of the seabed, form the uppermost part of a sediment sequence covering the rocks of the Barents Sea. This sediment sequence varying in thickness from a few to several hundred meters and was mainly deposited during the Quaternary (the last 2.6 million years), a time period where glaciations took place repeatedly.
Mud (clay and silt) – soft bottom sediments
During the last deglaciation (15 000-10 000 years ago), meltwater rivers carried large amounts of clay and silt to the ocean. Some of this was preserved in the deeper troughs on the continental shelf. However, subsequent lowering of sea level and strong bottom currents resulted in winnowing of finer grain-sizes (clay and silt) from the bank areas, and deposition of these sediments in the deeper parts. This characterizes much of the Bjørnøyrenna, Storfjordrenna and the deeper basins in the north and east of the Barents Sea.]]>
Climate variability affects fish in a variety of ways and throughout its life cycle. Sea temperature is the variable that has received the most attention from researchers in terms of its effects on both pelagic and demersal fish. Successful individual growth often occurs within a limited thermal range that differs among species and even between developmental stages within the same species. Generally, fish in colder waters tend to exhibit slower individual growth than those in warmer waters (Godø, 2003). ]]>
The demersal fisheries are highly mixed, usually with a clear target species dominating, and with low linkage to the pelagic fisheries (Table 2.5.2). Although the degree of mixing may be high, the effect of the fisheries varies among the species. More specifically, the coastal cod stock and the two redfish stocks are presently at very low levels. Therefore, the effect of the mixed fishery will be largest for these stocks. In order to rebuild these stocks, further restrictions in the regulations should be considered (e.g. closures, moratorium, and restrictions in gears).]]>
Area-surveys are conducted throughout the year. The number of vessels in each survey differs, not only between surveys but may also change from year to year for the same survey. However, most surveys are conducted with only one vessel. It is not possible to measure all ecosystem components during each survey. Also, an investigation should not take too long time in order to give a synoptic picture of the conditions. Therefore the surveys must focus on a specific set of quantities/species. ]]>
Standard sections contain some of our longest marine time series, reaching back more than 100 years.At the beginning of the 20-th century observations started on the Kola Section in the Barents Sea (Knipovich 1906), and by the 1930s, a network of such sections had been developed in the area (Figure 3.2.1). During the last decades, zooplankton has also been sampled at some of these sections. An overview of length, observation frequency and present measured variables for the standard sections in the Barents Sea is given in Table 3.2.1. Specific considerations for the most important sections are given in the following text.
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