Drastic parasitic infestations among cultured tilapias at El- Abbassa fish farms, Egypt, with respect to stressors of abiotic factors

The Egyptian expansion in fish aquaculture requests betterment in fish health management systems. This study was carried out to investigate the infestation prevalence of gill and skin parasites infecting the farmed tilapias at El-Abbassa fish farms with respect to abiotic factors. Water physicochemical parameters of culturing ponds were analyzed seasonally from March 2020 to February 2021. Results demonstrated that water quality measurements of fishponds were within normal values that cultured tilapia species can tolerate. Parasitological examinations of four different farmed tilapia species revealed critical parasitic infestations with Chilodonella hexasticha (Ciliate), Cichlidogyrus tilapiae (Monogenea)in addition to Lernaea elegans and Lamproglena monody (Copepoda). Detailed morphological characteristics and symptoms of infestations of the four parasites were mentioned. The highest prevalence of C. hexasticha (71.4%) infecting T. zillii was recorded during winter, while the highest percentage (100%) of C. tilapiae infesting O. niloticus, O. aureus and S. galilaeus was recorded during spring. Finally, the highest prevalence of the crustacean parasitic copepods (100%) infecting O. niloticus, T. zillii, and S. galilaeus was reported during autumn.  The total parasitic infestation rates were superior during summer while their minimal levels were recorded during winter, autumn, and spring, respectively. The intimate relationship between the intensity of infection with the monogenean gill parasite C. tilapiae and seasonal physicochemical parameters (temperature, dissolved oxygen, pH, nitrites, nitrates, visibility, total hardness, total alkalinity, salinity, total ammonia and unionized ammonia) were discussed briefly.