The present study was aimed to investigate the disease problems in some marine fishes were represented as Dicentrarchus labrax, D punctatus and Argyrosomus regius and collected from the fish farms of western region of Port Said. The parasites encountered were carefully removed, isolated and identified. The present study investigated the occurrence of Ergasilus sp. in Dicentrachus labrax, Lernanthropussp. in D punctatus and Argyrosomus regius The Ergasilus species parasitized (20%) of D labrax, Lernanthrropus, Parachamallanus, Rhabdochona parasitized (80%) of D punctatus and Anisakis simplex parasitized (4.9%) of A regius. The total prevalence was (6.7%).The main sites of parasitic infestation were the gill filaments, gut and ovaries. Besides, both phyto and zoo planktons in water ponds were analyzed and estimated. The relation between such plankton and fish parasites was discussed.