Distribution and growth of bivalve molluscs Macoma calcarea (Gmelin, 1791) in the Kara Sea

This study is devoted to the analysis of distribution and linear growth of Macoma calcarea in the southwestern part of the Kara Sea based on the results of observations (119 stations at depths from 4 to 415 m) in August-September 2012–2013. It appeared that for at least the last 100 years M. calc area has been a characteristic component of coastal bottom communities in the southwestern part of the Kara Sea and sometimes dominated by biomass. The densest beds of M. calcarea were confined to the silty biotopes at depths less than 50 m. Within this depth range, it was possible to associate the distribution of molluscs only with the characteristics of bottom sediments. The highest values of Macoma biomass and density (up to 90 g m − 2 and 120 ind. m − 2 , respectively) differed in habitats with a rather high content of silt in the bottom sediments (more than 80%), which quite logically corresponded to the trophic characteristics of this species. The influence of interspecific relationships on the distribution of Macoma was not revealed. The maximum size and age of M. calcarea (37 mm and 21 years, respectively) in the southwestern part of the Kara Sea, the average annual growth rate (about 2 mm/year) turned out to be close to those of this species in other areas of distribution. It was shown that the results of the age determination of specimens by the external morphology and inner marks (shell cross-sections) were quite comparable. Individual and group growth of Macoma were characterized by weak heterogeneity within the studied water area. The individual growth of molluscs, apparently, is mostly determined by the characteristics of the initial period of molluscan growth.