Monitoring

Introduction

Thu, 03 Dec 2009 11:13:50 +0000

To ensure the comparability of observation results and to estimate seasonal and year-to year variations in oceanographic variables, it was suggested in Stockholm as early as 1899 that measurements should be made at standard depths and on standard sections. At the beginning of the 20th 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).

Standard sections and fixed stations

admin@barentsportal.com (Administrator) — Wed, 09 Dec 2009 09:06:35 +0000

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.

Surveys

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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.

Surveys - Norwegian/Russian winter survey

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The survey is carried out during February-early March, and covers the main cod distribution area in the Barents Sea. The coverage is in some years limited by the ice distribution. Three vessels are normally applied, two Norwegian and one Russian. The main observations are made with bottom trawl, pelagic trawl, echo sounder and CTD. Plankton studies have been done in some years. Cod and haddock are the main targets for this survey.

Surveys - Lofoten survey

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The main spawning grounds of North East Arctic cod are in the Lofoten area. Echosounder equipment was first used in 1935 to detect concentrations of spawning cod, and the first attempt to map such concentrations was made in 1938 (Sund, 1938). Later investigations have provided valuable information on the migratory patterns, the geographical distribution and the age composition and abundance of the stock.

Surveys - Norwegian coastal survey

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In 1985-2002 a Norwegian acoustic survey specially designed for saithe was conducted annually in October-November (Nedreaas 1998). The survey covered the near coastal banks from the Varangerfjord close to the Russian border and southwards to 62° N. The whole area has been covered since 1992, and the major parts since 1988. The aim of conducting an acoustic survey targeting Northeast Arctic saithe was to support the stock assessment with fishery-independent data on the abundance of young saithe.

Surveys - Joint ecosystem autumn survey

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The survey is carried out from early August to early October, and covers the whole Barents Sea. This survey encompasses various surveys that previously have been carried out jointly or at national basis. Joint investigations include the 0-group survey, the acoustic survey for pelagic fish (previously known as the capelin survey), and the investigations on young Greenland Halibut north and east of Svalbard. The predecessor of the survey dates back to 1972 and has been carried out every fall since.

Surveys - Russian autumn-winter trawl-acoustic survey

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The survey is carried out in October-December, and covers most of the Barents Sea. Two Russian vessels are usually used. The survey has developed from a young cod and haddock trawl survey, started in 1946. The current trawl-acoustic time series of survey data starts in 1982, targeting both young and adult stages of bottom fish.

Surveys - Survey on estimation of abundance of young herring in the Barents Sea

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This survey is conducted in May and takes 2-3 weeks. It also includes observations of physical oceanography and plankton.

Surveys - Norwegian Greenland halibut survey

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The survey is carried out in August, and cover the continental slope from 68 to 80ºN, in depths of 400–1500 m north of 70º30’N, and 400–1000 m south of this latitude.