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In order to test the ability to produce antibacterial substances within marine bacteria, prior to select potential probiotics for use in shellfish farming, we targeted a large collection of bacterial isolates (132 strains), brought from the clamRuditapes decussatus and 37 reference strains. First, we proceeded to their biochemical identification and the screening of antibiotic resistance profiles. Else, we investigated their inhibitory activityin vitro against several fish and shellfish pathogens, using two methods: the double-layer agar and the direct simultaneous antagonism methods. The results showed high frequencies of inhibitory producing bacteria (IPB) within the isolates. These bacteria (25%) were aerobic mesophylic bacteria belonging to various bacterial groups: 33.7% oxidase-positive Gram-negative bacteria, 7.4%Enterobacteriaceae and 28% lactic acid bacteria. Besides this group, nine strains produced strong inhibition effect. These bacteria belonged to:Aeromonas hydrophila, Aeromonas sobria, Pseudomonas cepacia, Vibrio sp,Serratia liquefaciens andLactobacillus rhamnosus. They were active against pathogenic bacteria belonging to the genera:Aeromonas, Pseudomonas andVibrio. These potential probiotics were submitted to further investigations prior to their introduction in larval shellfish farming.