Abstract

Aquaculture production has become increasingly important for ensuring food security, supported by the expanding variety of cultivated species. This study evaluated the effects of different water environment characteristics on the differential leukocyte counts of the Nile tilapia (Oreochromis niloticus), a key farmed fish species in Africa. Fish from four different water sources were compared with healthy individuals from the natural water of the Nile River. A total of 64 Nile tilapia, each weighing 80–100 grams, were evenly divided into four groups and maintained at temperatures ranging from 25.00± 2.5°C to 30.00 ± 2.5°C. The groups included fish from experimental tanks (ET), ponds managed by the General Administration of Fisheries Ponds (GAFP), the Fisheries Research Center Ponds (FRCP), and the White Nile River (WNR, control). Significant differences in water quality parameters, particularly NH₄, NH₃, NO₃, and NO₂ concentrations, were observed among the water sources. GAFP and ET waters showed higher concentrations of these compounds (NH₄, NH₃, NO₃, and NO₂) compared to FRCP and WNR. Differential leukocyte counts varied significantly across the groups. The ET group showed the highest eosinophil percentage (9.68 ± 0.44%), while the GAFP group exhibited the highest percentages of lymphocytes (46.40 ± 0.13%), monocytes (15.43 ± 0.14%), and neutrophils (18.31 ± 0.16%) compared to WNR. In contrast, the FRCP group recorded the highest platelet percentage (32.34 ± 0.49%), while the ET group had the lowest (13.65 ± 0.15%). Additionally, the ET group recorded the highest overall white blood cell count (191.46 ± 0.61 × 10³). A strong positive correlation was found between the blood profiles of Nile tilapia and the water environment parameters. This study highlighted significant differences in water quality among experimental groups, with FRCP and WNR showing lower parameters. In addition, examining white blood cells in fish is crucial for biological monitoring of surface water pollution.