Arctica (Cyprina) islandica in Kiel Bay (Western Baltic): growth, production and ecological significance

Abstract

The growth of the ocean quahog Arctica islandica L. was investigated with data from two sites of Kiel Bay, Western Baltic. At the experimental site “Benthosgarten” (BG), length-increment data were obtained from a colonization experiment and from implanted and resampled clams. At the “Millionenviertel” site (MV), clams were caught by dredging. Length-increment data were obtained from annual growth bands formed at the surface of the shell. A Von Bertalanffy growth function was fitted to both data sets. Growth at the BG site ( K = 0.35, L ∞ = 60.6 mm) was different from that at the MV site ( K = 0.07, L ∞ = 93.6 mm). The BG site growth parameters are assumed to be strongly biased due to the experimental set-up. Growth of the MV site population is similar to Atlantic populations of A. islandica but maximum age and length are much smaller in Kiel Bay. The annual P B ̄ ratio of the MV site population was estimated to be 0.34, which results in an annual production of 15 g AFDW · m −2 in this particular area. Total annual production in Kiel Bay is estimated at ≈ 11000 t AFDW, ≈40% of the estimated annual benthic community production. A. islandica is eaten mainly by cod Gadus morhua. During 1970–1985, ≈40% of the annual production of cod in Kiel Bay is estimated to have depended on this clam.