DOI: 10.2478/cjf-2026-0003
Original scientific paper
SPATIAL VARIABILITY IN GROWTH AND CONDITION OF NILE TILAPIA (Oreochromis niloticus) LINKED TO POLLUTION GRADIENTS IN THE NILE RIVER, EGYPT
2026, 84 (1) p. 29-38
Fatma Ahmed, Mahmoud Farrag, Ezat Abdallah, Khaled AbouelFadl
Abstract
This study investigated the spatial variations in the growth, condition, age, and longevity of Oreochromis niloticus populations along a pollution gradient in the Nile River, Aswan, Egypt. We compared a reference site (Frial, Site I) with two polluted sites: the El-Sail Drain (Site II) and Kom Ombo (Site III). Water and fish samples were collected monthly from January to December 2021 to analyze the physicochemical parameters, heavy metals, age structure, growth, and condition factors. The results reveal significant spatial disparities. Fish from the Frial site exhibited the highest growth potential, with an asymptotic length (L∞) of 27.22 cm, growth coefficient (K) of 0.17 year⁻¹, and maximum age of 13.5 years. In contrast, populations from El-Sail Drain and Kom Ombo showed reduced growth (L∞ = 25.46 and 24.52 cm, respectively), higher K values (0.19 and 0.24 year-1, respectively), and shorter lifespans (11.9 and 9.2 years, respectively). Although the growth performance index (φ) was similar among sites, annual length increments and condition factors were significantly lower at polluted sites. These findings demonstrate that environmental degradation, primarily from industrial and domestic wastewater, adversely affects the somatic growth and physiological conditions of Oreochromis niloticus, highlighting the urgent need for enhanced pollution control and management strategies in the Nile River.
Keywords
Age structure, Fisheries, growth, pollution and River Nile
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