Document Type : Original Article
Authors
1
Central Laboratory for Aquaculture Research, Agricultural Research Center, Abo-Hamad, Sharkia, Egypt
2
Fish Production Department, Faculty of Agriculture, Al-Azhar University, Nasr City, Cairo 11884, Egypt
3
Central Laboratory for Aquaculture Research, Agriculture Research Center, Sakha, Kafr Elshiekh, Egypt
10.21608/ejabf.2025.439975.6947
Abstract
Aquaculture is a vital pillar of global food security, particularly for Egypt, as it is the principal fish-producing sector. Heavy metal contamination in aquatic environments represents one of the most significant environmental hazards. A 90-day feeding experiment was conducted to evaluate the effects of sublethal concentrations of heavy metals: Cu (0.125 ppm), Hg (0.005 ppm), Pb (1.5 ppm), and Cd (1 ppm) on the Nile tilapia. The investigation focused on evaluating growth performance, somatic indices, metal accumulation in tissues, and key physiological parameters. 144 fish (initial weight, 17 ± 0.4 g) were divided at random in triplicate into 12 glass aquaria (90 L each), placed into four treatment groups for heavy metals and control. Fish received a commercial feed containing 30% crude protein, administered at 3% of their body weight per day. Heavy metal exposure resulted in dramatic decreases (P≤ 0.05) in the mean weight gain, specific growth rate, and percentage survival compared to control. Both feed conversion ratio and protein efficiency ratio were markedly reduced, indicating a decline in feed utilization efficiency. Residue analysis revealed the greatest accumulation of heavy metals in the kidney and liver, with lesser amounts detected in the gills and muscles, highlighting the liver's role in detoxification. Significant changes (P≤ 0.05) in hepato-, spleen-, and kidney-somatic indices are indicative of organ injury. Moreover, biochemical examination revealed a decrease in total protein and globulin concentration. In addition, increased serum activities of hepatic enzymes (ALT and AST) indicate hepatocellular damage. Hemogram profile examination established that hemoglobin concentration, packed cell volume, and counts of erythrocytes and leukocytes were significantly higher (P ≤ 0.05) in control fish compared to those exposed to heavy metals. Results indicate the acute physiological distress and hematobiochemical change resulting from metal exposure, and highlight their bioaccumulation and toxicological effects in freshwater habitats.
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