Population characteristics of the bivalve mollusk Macoma calcarea (Gmelin, 1791) in fjords with different hydrological regime (Svalbard)

The features of the distribution and biology of the bivalve mollusk Macoma calcarea in the fjords of Western Svalbard with different hydrological regimes in 2019 have been established. Two groups of settlements are distinguished, differing in terms of abundance, size and age structure, and growth rate. The most favorable conditions for the formation of colonies with high abundance, diverse size and age structure, and high lifespan of M. calcarea were noted in the Atlantic and transformed Atlantic water masses with a temperature of more than 2 oC in Grenfjord Inlet and Koles Bay, due to the influence of the warm Atlantic currents. The least favorable conditions are typical for fjords with negative water temperatures and high salinity in the layer of winter water masses (Sturfjord), where an unstable settlement with low abundance, high growth rate and shorter life expectancy has formed.