Effects of particle concentration and season on the filtration rates of the freshwater clam, Sphaerium striatinum Lamarck (Bivalvia : Pisidiidae)

The effects of particle concentration and season on the filtration rates of the freshwater clam S. striatinum Lamarck were assessed by measuring clearance rates of small (2.02 mu m) latex beads from dilute suspensions. Filtration rates decreased as particle concentration increased over a range of 2-64 mg l super(-1), with rates decreasing in similar proportion for clams of all sizes. For a 1-mg clam, rates decreased from approximately 8.4 to 0.57 ml clam super(-1) h super(-1). Seasonal filtration rates for adult clams peaked during periods of greatest reproduction. The patterns for smaller clams are similar, though proportional changes in filtration rates differ for various sizes of clams.