Vital economic threat of predatory birds and parasites to cultivated fishes in Egypt

Abstract

Despite continuing worldwide expansion in production and demand, recent performance in the aquaculture sector in Egypt has been volatile, and yield has reduced. The most significant and visible problems arise from parasitic diseases and predation by birds. In this study, we examine the impact of local parasite fauna and bird predation in relation to economic loss in fish farms, with a focus on the importance of water quality. Water, fish, and bird samples were obtained from private fish farms at El-Abbasa in northern Egypt. Results showed significant (P < 0.05) production losses between 54.08 ± 1.88% and 62.11 ± 2.37%. Eleven predatory bird species were observed, with two species feeding in a variety of ways. The estimated total loss from fish eaten by predatory birds was ~1.59 tons over the six-month production cycle, valued at USD 1, 990. The studied fish had high rates of parasitic infestation: 63.89% in Oreochromis niloticus (Nile tilapia) and 75.85% in Clarias gariepinus (African sharptooth catfish). Zoonotic fish parasites that may constitute a health hazard for those consuming the farmed fish were recovered. Hemato-biochemical indices showed significant decreases in red blood cell count, hemoglobin, and total protein, and significant increases in white blood cell count, activities of alanine aminotransferase and aspartate aminotransferase, and levels of glucose and uric acid in parasitized fish. Water physicochemical factors deviated significantly from norms in the majority of metrics. This study's results could help us gain a better understanding of production losses at fish farms. Overall, the combined effects of predation by birds and parasite infection increased fish loss and resulted in significant negative economic effects at fish farms.