Population dynamics, growth, and production of the Asiatic clam,Corbicula fluminea, in a blackwater river

Abstract

In a sixth-order blackwater river (Lower Coastal Plain of Georgia, USA), the average life span of Corbicula fluminea (Müller) was 3–4 years, with shell length reaching only 18–20 mm by the third year. Mean density was usually < 200/m2over a 43-month period, but > 1000/m2in population centers. Mean biomass (dry mass of soft tissue) was consistently 1–5 g/m2, but averaged 11 g/m2in population centers. Biomass growth rates of clams reared in situ were highest in late spring and were inversely related to clam mass. Production ranged from 0.18 g∙m−2∙year−1at a main-channel site to 3.2 in a backwater and averaged 1.2–1.7 for 2 consecutive years. In population centers, production reached 9–23 g∙m−2∙year−1. Production was highest in spring and fell to zero in winter when growth ceased. Annual production/biomass values were about 4–8 for first-year individuals, but ranged from 0.51 to 1.78 overall. Individual size, growth rates, and production all indicated that this blackwater river was a stressful environment for Corbicula, probably due to low alkalinity (< 30 mg/L as CaCO3). Unlike its effect in many other systems, the clam appears to play a minor role in the trophic dynamics of this river.