Growth of the Barents Sea capelin (Mallotus villosus) in relation to climate

The history of capelin assessment in the Barents Sea has shown that the growth of individual capelin has varied between years and different parts of the capelin distribution area. As the number of individuals in this stock is very high, even small changes in individual growth will affect the surplus production and the catches which may be taken from it. If this growth could be estimated in advance, the assessment could be made more precise. Temperature variation has been suggested as a factor which could be partly responsible for the variation in growth. To study this possibility, we compared corresponding values of temperature and length increment of the capelin in different parts of the Barents Sea from 1976 to 1985. The mean temperature in subareas was calculated by averaging the temperatures for the depth interval 10-200 m at all of the hydrographical stations taken each September in each statistical square which the sea is devided, and then combining the squares to form subareas. The estimates of growth were calculated by substracting the backcalculated length corresponding to the outermost winter ring in the otolith from the length at sampling. A positive covariance between water temperature and growth was indicated when all the material was considered, but no clear correspondance was found between temperature and growth within subareas

Physical oceanographic investigations in central parts of the Barents Sea, July 1979

A limited area of the marginal sea ice zone in the Barents Sea was investigated in the period 9-19 July 1979 with the intention of describing the biological production system in the vicinity of an ice edge. This paper describes the physical oceanographic conditions in the observation period. Two main sections, I and II, and three auxiliary sections, A, B and C, were worked out (Fig. 1). Section II was covered twice with 6 days interval between each coverage. All sections were characterized by a homogeneous surface layer of about l0 m. Below this there was a transition layer, which in both sections was most pronounced in the northern part. In section II a tongue of cold Arctic water was penetrating southwards below the transition layer. This tongue was also observed in the sections A, B and C. The second coverage of section II showed that the southern part of the tongue was in process of being mixed with surrounding water masses. During this coverage the surface temperature was 2-4°C higher than during the first coverage. This was due to heating by short wave radiation from the sun and was calculated to be 3.2°C in the upper 10 m. Two anchor stations of duration 30 hours were made at two locations in section II, one in the southern part and one in the northern part. There was insignificant variations in the hydrographical conditions during these 30 hours at both stations. At both anchor stations current measurements were carried out with Gytre current meters. In addition, at the southern anchor station, current was measured for 8 days with 4 Aanderaa current meters suspended from a subsurface buoy. All current measurements showed small velocities, and both speed and direction changed very little with depth

A review of the sea ice conditions of the Barents Sea and the area west of Spitsbergen

The purpose of the present paper is to review our knowledge of the sea ice conditions of the Barents Sea and the area west of Spitsbergen and is mainly based on available literature. The variations of the sea ice conditions may be regarded to be of three different types. Short-term variations take place within periods from a few hours to about one month. On some occasions the position of the ice border during one week can vary more than 100 km. The seasonal variation of the sea ice extension is, in its broad features, similar from one year to another. Nevertheless, great interannual variation in the position of the ice border may occur. In some months these variations exceed 500 km. There seems to be no connection between freezing in winter and melting in summer. Cyclic variations in the ice conditions of periods between 3-5 years have been proposed. Also a period of 11 years, which coincides with the solar activity cycle, has been put forward. However, the verification of these periods is not convincing. In addition long-term trends are observed. The main characteristic feature of the sea ice distribution is caused by permanent warm and cold currents in the area. There also seems to be a connection between the heat content of the Atlantic water which enters the Barents Sea, and the extension of the ice in winter. How far the ice withdraws in summer depends on local meteorological conditions only. On the west coast of Spitsbergen, however, there appears to be a connection between extreme hydrographic situations and extremes in distribution of ice also in the summer. Considering the meteorological conditions, most attention has been focussed on the effects of air temperature, air pressure and prevailing winds. Some authors have found corresponding variations in air temperature and ice conditions, while others have dealt with the relationship between air pressure differences and ice extension. These studies indicate a correspondance between the sea ice conditions and the atmospheric circulation. However, variations in the atmospheric circulation also affect the intensity of ocean currents and vice versa. This intercorrelation complicates the task of identifying the most significant factors influencing the variations of the sea ice

The climate in the Barents Sea in 1983

The present paper describes the temperature and salinity conditions in the Atlantic inflow to the Barents Sea in three hydrographic sections in 1983. Both temperature and salinity show increasing values in 1983 compared to 1982, especially in the eastern Barents Sea. Compared to the mean temperature for the period 1977-83, the temperature in 1983 was about 0.8° higher in all three sections. The ice conditions are also briefly discussed. There was considerably less ice in 1983 than in the six previous years

On the northerly distribution of capelin and temperature conditions in the Barents Sea in autumn

Except for 1972, investigations on the Barents Sea capelin stock have been carried out within the period 10 September - 15 October since 1971 by the Institute of Marine Research. These investigations have revealed variations in the geographical distribution of capelin during the period 1971-80. The present paper concentrates on the influence of temperature on the capelin distribution. The influence of ice is also briefly discussed. The distribution area of capelin, north of 76°N and between the meridians 27°E and 55°E, is compared with the temperature at 100 m and ice conditions in the same area. The relation between temperatures and northerly distribution of capelin is fairly good, while there is no relation between ice conditions and capelin distribution. The results also indicate that 3 and 4 years old capelin prefer water colder than 2°C