Sixteen isolates of Aeromonas hydrophila andone isolate each of Aeromonas sp. n., Aquaspirillum sp., Pseudomonas sp., and Streptococcus sp., isolated from normal, apparently normal and epizootic ulcerative syndrome (EUS)-affected fish were screened for siderophore production at 20, 25, 30, and 37^oC. results showed that siderophore production of A. hydrophila and Aeromonas sp. n. isolates decreased with increasing temperature. Among A. hydrophila isolates, 81.2% produced siderophore at 20^oC, 50% at 25 and 30^oC, and only 37.5 at 37^oC. In contrast, Aquaspirillum sp., Pseudomonas ep., and Streptococcus sp., showed higher production of siderophore at 30 and 37^oC.