Monogenean parasites are the most ubiquitous and abundant parasites in the aquatic environment. In confined and stressful rearing conditions, their population easily can overpass their usual balance, proliferate and induce serious and hard-to-eradicate diseases. During a 9-month period, seven facilities along the Adriatic coast were monitored for the presence, prevalence and abundance of these parasites. Only three monogenean species - Diplectanum aequans, Lamellodiscus elegans and Sparicotyle chrysophrii - were isolated from only three cage-reared hosts - Dicentrarchus labrax, Sparus aurata and Diplodus puntazzo - but without clinically visible symptoms. Parasite population dynamics showed a strong relationship with environmental factors such as salinity and temperature and marked host specificity.