Pespiration and Some Features of Nutrition of the Oysters Crassostrea rhizophorae Guilding

The natural distribution of oysters was investigated on mangroves in the bay of Ortigoza. Hydrobiological characteristics of the investigated region are given. The altitude of the horizon inhabited by oysters is 30 cm, the number of oysters is 44—371 per m², the biomass is 0.3—2.1 kg/m², the maximum oyster size is 7—8 cm when the bogy weight is 3.6 g, the calorific value is 4.35—5.24 kcal per g of dry matter. Equations are obtained for the dependence of oyster body dry weight (y) on the wet weight (x) — у = 0.1736x — 0.0008, and for the dependence of the wet weight on the total weight with the valves (z) — x = 0.1355z — 0.0010. It is shown that oysters adapt well to sudden exchanges of environmental factors (salinity, existence of mollusks outside water) and that the metabolism of oysters is very stable. The dependence of respiration Q (ml O₂ per a representative in one hour) on the animal body dry weight (W) at 25° С is expressed by the equation Q = 3.03W⁰·⁹⁸. Respiration intensity is calculated per body Wet weight and total weight. The value of the consumption and assimilation of the algae Ankistrodesmus braunii and Sceletonema costatum by oysters is determined, when the alga concentration varies in the medium. The average daily diet value when feeding on A. braunii was 3% of body weight and on S. costatum 75%. When the oyster size increases the daily diet value per unit weigth decreases. The quantity of assimilated food per unit weight does was practically independent of the body weight. Assimilation of A. braunii was 8—70% and that of S. costatum was 6—35% depending on the animal age. The energetic requirements of oysters and the degree of their provision are determined when oysters feed on the indicated algae. The daily energy balance is given. The industrial output of oysters on calculation (about 35 kg/m2) and the quantity of matter and energy necessary for providing their physiological processes are calculated