Size-Age Structure of Navaga Eleginus nawaga in the White, Barents, and Kara Seas

Abstract

Based on long-term data (1959−2017), a comparative analysis of the size–age structure of eight navaga Eleginus nawaga populations in the White, Barents, and Kara seas was carried out. The relationship between the growth rate of the navaga and the duration of the period with the optimum water temperature for feeding (0−12°C) was revealed. Individuals of the same age groups have the largest sizes in the central part of the range (Mezen Bay and the White Sea Voronka, Cheshskaya Bay of the Barents Sea), and the smallest ones in Pechora Bay of the Barents Sea. The higher growth rate of navaga in the northern part of the range (Kara Bay of the Kara Sea) compared with the southern (Onega Bay of the White Sea) is explained by the absence of heating of coastal waters above the limit favorable for feeding. The increase in the average size of the navaga of the populations under consideration in 1991–2017 relative to those in 1960−1990 is due to the lengthening of the period with a temperature >0°C for almost 1 month. In Mezen Bay and the White Sea Voronka and in the Barents Sea bays, the average length and weight increased only in the younger age groups, and they hardly changed or even decreased in the older ones. This was the result of an increase in the number of fish of older age groups in these areas as a result of a reduction in catch.