Investigations have been carried out with a view to see the effects of the introduction of petroleum microorganisms in the diet of cultivated marine fishes. Sea bream, Chrysophrys major, was used as the experimental fish. Studies were made by comparing the growth rates and blood properties of fish under two types of feeding i.e. one when fed on a diet containing petroleum microorganisms and the other when fed on a diet of fish meal alone. Results can be summarized as follows:
i) The mortality rate remains almost the same.
ii) The body size and growth rate do not differ significantly.
iii) Anatomical observations do not reveal any change in the morphological structure of the visceral organs.
iv) Hemoglobin concentration, hematocrit values, and plasma glucose concentration remain almost the same.
v) Cholesterol concentration and alkaline phosphatase activity in plasma are lowered by the introduction of petroleum microorganisms in the diet. This lowering is significant especially in the latter case.
Physiological mechanisms causing such differences in the blood properties, yet remain to be understood.