Escherichia coli and Vibrio cholerae strains were inoculated separately, and together, to aquatic microcosms containing water of 7–25‰ salinities. V. cholerae could be recovered for up to 56 days if sediment was stirred before sampling, but for only 14 days from the unstirred water column. E. coli could be recovered for no more than 7 days, and lost its metallic sheen characteristic on EMB or Endo agar after 24 h, and the characteristic blue colony color on M-FC agar was lost by fecal strains after exposure to salinity for 48–72 h. Results reported indicate that the coliform criteria for harvest of shellfish in estuarine waters needs critical re-evaluation.