Shellfish as a foodstuff must meet sanitary quality objectives for the protection of consumers and this quality is closely linked to the water. The oyster industry considered this challenge related to contaminations and currently, the major risk of disease is due to the presence of norovirus (NoV) since all oyster-consuming countries report outbreaks of gastroenteritis linked to the presence of this microorganism. Ultrafiltration has already demonstrated to be efficient for viral protection of oyster farms in previous studies. In this work, retention by ultrafiltration of Tulane virus, a NoV surrogate, was evaluated. The effect of virus concentration in the feed on the ultrafiltration efficiency has been assessed. Low retentions of about 1 log were observed at the lowest viral concentrations. At higher concentrations, an increase of retention up to 5 log was obtained. These results highlight the potential overestimation of UF efficiency during laboratory experiments realized at high concentrations, compared to low concentrations found in environmental resources. In agreement with other studies, higher retentions at high concentrations could be explained by formation of viral aggregates, which could facilitate the steric exclusion but also modify the electrostatic and hydrophobic interactions between isolated viruses/aggregates and membrane. Virus retentions with a fresh mineral water (Evian water) and seawater were compared. Seawater achieved higher retention rates for Tulane virus due to the membrane fouling.