Effect of temperature and body size on food utilization in the marine pearl oyster Pinctada fucata (Bivalvia: Pteridae)

Physiological parameters such as clearance rates, absorption efficiency, oxygen consumption and ammonia excretion were estimated for four size groups ranging from 16 to 60 mm in Dorso Ventral Measurements (DVM) of the marine pearl oyster Pinctada fucata at different water temperatures and the results were integrated by means of two physiological indices, namely Scope For Growth (SFG) and Net Growth Efficiency (K2). The rates of clearance, oxygen consumption and ammonia excretion were found strongly correlated (p ≤ 0.01) with size groups (as tissue dry weight) at water temperature from 18o to 31ºC. Absorption efficiency ranged from 43.2 to 56.9 % and was not related to body size in the tested temperature range. Oxygen consumption and ammonia excretion increased with temperature within the same size group from 18º to 31ºC. Clearance rate increased with temperature from 18º to 28ºC, but declined with further increase of temperature to 31ºC. Excreted energy contributed 2.4 to 4.0% to the total absorbed energy for different size groups and water temperatures. The SFG and K2 were higher at 26º and 28ºC and were minimum at 18ºC for all the size groups. The result showed that the optimum physiological conditions for survival and growth of P. fucata were in the temperature range of 26º to 28ºC