Energy budget for a stream population of the freshwater clam, Sphaerium striatinum Lamarck (Bivalvia: Pisidiidae)

An annual energy budget was constructed for a stream population of Sphaerium striatinum. The annual productivity (P) was 2.79 g C∙m−2∙year−1 and the average standing crop biomass (B) was 0.58 g C∙m−2; the resulting annual P:B ratio of 4.58 is below that expected for a bivoltine animal. The low value for reproductive effort (Re:P = 16.1%) may partially be attributed to the ovoviviparous, iteroparous nature of this population. A strategy of partitioning a large proportion of production to growth (G:P = 83.9%) may insure a high probability of attaining the minimum size necessary for reproduction. Production accounts for 44% of assimilation (A) with 56% of A lost through respiration. The net production efficiency (P:A = 44%) is high and indicates that this population is efficient in partitioning energy to growth and reproduction. The population must consume (C) 10.57 g C∙m−2∙year−1 to meet its energy needs. Only 35% of this could be accounted for by filter feeding; the remainder may have come from deposit feeding. Comparisons of P, P:B, Re:P and P:A with published values for corbiculacean clams indicates that this population of S. striatinum is one of the most productive and efficient in its energy partitioning of populations studied to date.