Growth, reproduction and production of Lissarca notorcadensis (Bivalvia. Philobryidae) in the Weddel Sea, Antarctica

Abstract

Growth, reproduction and production of the epizoic bivalve Lissarca notorcadensjs were compared between 2 regions of the Weddell Sea, the South Orkney and South Shetland shelves (north of 63" S) and the southeastern continental shelf (south of 70' S). Growth lines on the shell surface were interpreted as annual growth marks. Von Bertalanffy growth functions were fitted to length-at-age data for the northern region (L, = 12.140 mm. K = 0.085 yr-', t o = -1.477 yr) and for the southern region (L, = 9.802 mm, K = 0.112 yr-l, t o = -1.247 yr). Female gonad production was estimated from the number of embryos brooded per female, embryo mass at release and the fraction of females in the population. Somatic production was calculated from weight specific growth rates. Annual somatic and gonad production/biomass (P/B) ratios were 0.316 and 0.151 (north), and 0.305 and 0.132 (south), respectively. These values are lower than P/B ratios of boreal mollusc populations of comparable mean body mass.