Influence of size, habitat and food concentration on the feeding ecology of the bivalve, Meretrix meretrix Linnaeus

Abstract

Meretrix meretrix Linnaeus was held in a simulated natural culture system to measure particular physiological parameters. Results showed that both clearance rate (CR) and ingestion rate (IR) were related exponentially to body size (dry flesh weight; W), as defined by the formulae CR=0.47 W 0.63, IR=0.95 W 0.60. Body size had no effect on absorption efficiency (AE) at temperatures of 10, 16 and 22 °C, but, within this temperature range, AE increased significantly with increasing temperature. Feeding of M. meretrix was greatly improved when the clams were held in a substrate compared to holding them on the bare bottom of the tank. When held in a sand substrate, the CR and IR were four times higher and, in a silt substrate, three and two times higher than in clams held on the bare tank bottom. AE also improved in clams held in sand (21% increase) or silt (11% increase) compared to clams not held in a substrate. Results show that within the range of the food concentration [defined as particulate organic matter (POM)] used, 2.30±0.21 to 6.15±0.13 mg POM l −1, the relationships between POM and CR and IR were exponential with relatively poor significance and are described by the formulae CR=0.27 [POM] 0.91, IR=0.32 [POM] 1.33. It was found that the saturated food concentration level for CR and IR for this clam species at the optimal feeding temperature of 22 °C was about 8 and 6.33 mg POM l −1, respectively. The food concentration threshold for pseudofaeces excretion was found to be 2.06 mg POM l −1. There was no marked influence of food concentration on absorption efficiency, which was consistently about 55%.