Growth and production of Hiatella arctica (Bivalvia) in a high-Arctic fjord (Young Sound, Northeast Greenland)

Abundance and biomass of the bivalve Hiatella arctica (L.) was investigated at depths from 10 to 80 m along 6 transects in the high-Arctic fjord Young Sound, NE Greenland (74degrees 18.58'N, 20degrees 15.04'W). The highest abundance was found at a depth of 20 m, and the mean intertransect density at this depth was found to be 57 ind. m(-2) with a biomass of 6.2 g shell-free dry weight (SFDW) m(-2). Age was estimated by counting annual growth rings in acetate peels made by cutting through the umbo region. The age of the oldest individual was estimated to be 126 yr. The Von Bertalanffy growth function fitted to length-at-age data showed that a maximum shell length (L-infinity) of 37 mm was attained in approximately 35 yr. The mean annual growth rate was 0.14 yr(-1) corresponding to a mean annual production of 0.30 g SFDW m(-2) (depth 10 to 60 m), The annual somatic production-to-biomass ratio was 0.095. The size distribution of clams was bimodal with a group of very small (shell length 6 to 8 mm) individuals and another group of individuals around the maximum shell length. Large individuals are relatively abundant as a result of their long life span and the absence of significant mortality agents in this area. Based on production estimates, the carbon demand of the H. arctica population accounts for 3.6 % of pelagic production in outer Young Sound.