INFLUENCE OF FOOD CONCENTRATION ON THE PHYSIOLOGICAL ENERGETICS AND GROWTH OF OSTREA-EDULIS LARVAE

Feeding, respiration and growth rates of oyster (Ostrea edulis L.) lar vae reared at five food levels were measured throughout the entire lar val period. Energy budgets were derived as a function of algal (Isochr ysis galbana Parke) food concentration. Ingestion rate (IR, cells h(-1 )) and oxygen consumption rate (V-O2, nl h(-1)) were almost isometric functions of larval size [ash-free dry weight, (AFDW, mu g)], characte rized by the equations: IR = 803.9 AFDW(1.13) and V-O2 = 4.85 AFDW(1.0 9). Ingested ration was directly correlated to cell concentration up t o a maximum at 200 cells mu l(-1), with further increases failing to s upport higher ingestion rates. Likewise, growth rate linearly increase d with food ration up to 100 cells mu l(-1) (max. growth efficiency, K -1 = 25%) and reached a maximum at 200 cells mu l(-1) (growth rate = 5 .6 mu m d(-1)), with further increases in food not supporting signific antly 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 fe eding schedule of 50, 100 and 200 cells mu l(-1)from Days 0, 5 and 10, respectively, is recommended.