In order to study on feeding of O. ruber, sampling was carried out monthly from Nov. 96 to Aug. 97, stomach contents of 691 samples were examined of which, 67% were empty and 33% had feed residues. Index of being vacant was higher in males in comparisan with females, this index reaches at maximum from Feb. to May for males and in Aug. and Jan. for females. Fish was found in 58% Of the stomach, shirmp in 39% andfish and shrimp in 3% of them. During a year feeding intensity did not show a regular pattern and it was weak. Relative importance index for fish and shrimp was 63% and 37% respectively. The main food of immature fish was shrimp, which as they grow shrimp replaced by fish as the main food, so O. ruber is a carnivorous and hunter species.
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