Influence of food concentration on the physiological energetics and growth of Ostrea edulis larvae

Abstract

Feeding, respiration and growth rates of oyster (Ostrea edulis L.) larvae reared at five food levels were measured throughout the entire larval period. Energy budgets were derived as a function of alga (Isochrysis galbana Parke) food concentration. Ingestion rate (IR, cells h-1) and oxygen consumption rate ( VO2 , nl h-1) were almost isometric functions of larval size [ash-free dry weight, (AFDW, μg)], characterized by the equations: IR=803.9 AFDW1.13 and VO2 =4.85 AFDW1.09. Ingested ration was directly correlated to cell concentration up to a maximum at 200 cells μl-1, with further increases failing to support higher ingestion rates. Likewise, growth rate linearly increased with food ration up to 100 cells μl-1 (max. growth efficiency,K 1=25%) and reached a maximum at 200 cells μl-1 (growth rate=5.6 μm d-1), with further increases in food not supporting significantly faster growth. Maintenance ration was 2 to 3% daily dry weight (DW); optimum ration increased during larval development from 5 to 20% DW; maximum ration was 20% DW. During larval rearing, an increasing feeding schedule of 50, 100 and 200 cells μl-1 from Days 0, 5 and 10, respectively, is recommended.