Seasonal Survey on Common Parasitic Diseases in Dicentrarchus labrax, Dicentrarchus punctatus and Sparus aurata Collected From Lake Timsah, Egypt

This study aimed to identify parasitic species infesting marine fish collected from Lake Timsah across different seasons. A total of 480 marine fish of varying species, weights, and lengths (160 Dicentrarchus labrax, 160 Dicentrarchus punctatus, and 160 Sparus aurata) were randomly collected seasonally from September 2020 to August 2021. Most examined fish showed no pathognomonic clinical abnormalities and appeared normal. However, some D. labrax exhibited hemorrhages on the mouth, operculum, around the eyes, and at the bases of their fins, along with abdominal distension and emaciation. Infested D. punctatus showed excessive mucus and a mosaic appearance of the gills. Infested S. aurata displayed no external clinical abnormalities, except for some hemorrhagic lesions and slight abdominal distension. The total prevalence of parasitic infestation among the examined fish was 57.91%. The highest infestation rate was observed in D. punctatus (74.38%), followed by D. labrax (71.25%) and S. aurata (28.13%). The isolated parasites included nematodes (Hysterothylacium aduncum, Anisakis simplex larvae, and Contracaecum spp. larvae), digeneans (Erilepturus hamate and Tangiopsis chinensis), crustacean parasites (Lernanathropus kroyeri, Caligus minimus), and isopods (Livoneca redmanii). The total parasitic infestation rate varied significantly across different seasons (P<0.001), with the highest rate in winter (81.6%), followed by spring (70.8%), autumn (55%), and summer (24%). Several factors, such as season, fish species, and differences in body weight and length, affect the infestation rates.