Clearance rates and ingestion efficiency of the Japanese scallop Patinopecten yessoensis
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In coastal ecosystems, variations in food quantity may have significant effects on the clearance and ingestion rates of suspension-feeding bivalves. In this study, clearance rates and ingestion efficiencies were determined for Japanese scallop (Patinopecten yessoensis) juveniles (60.6±4.5 mm in shell height) under laboratory conditions. Scallops were kept individually in glass beakers at 15°C and fed with different cell numbers of Pavlova sp. (0.8 to 57.60×106 cells) to provide a wide range of food quantity as particulate organic carbon (POC). Clearance rates (CR) and ingestion efficiencies (IE) were estimated by monitoring POC concentration over a two-day period, and from 2 to 14 days of feeding, respectively. Both CR and IE were significantly influenced by POC concentration. CR ranged from 15.8 to 38.5 mL ind-1 h-1 (or 8.9 to 49.6 mg Ch-1 g dry weight-1) with maximum values at high POC concentrations. IE varied from 40 to 71% and differed significantly between the lowest (2,900 μg C L-1) and highest (8,000 μg C L-1) food rations. The feeding response of juvenile scallops to different POC concentrations was fitted to a power curve equation: IE (%)=0.9272×POC0.5105, r=0.98. Extrapolated field-based estimates of IE ranged from 7.8 to 12.7% in response to seasonal changes in POC concentration (64.5 to 168.6 μg C L-1). It is concluded that particle filtration rates by juvenile scallops are related to food quantity, as suggested by both field and laboratory-derived feeding rates.