Effects of Canal Lining on Ichthyofaunal Diversity in Southern Punjab, Pakistan

Effects of Canal Lining on Ichthyofaunal

Abstract

Canal lining is extensively applied in order to enhance the efficiency of irrigation, but its ecological effects on aquatic organisms are not studied properly. Objectives: To evaluate how canal construction materials influence ichthyofaunal diversity and water quality in Southern Punjab, Pakistan. Methods: Lined and unlined canals were compared in terms of a comparative field study, which was carried out through ecological survey and physico-chemical studies. Standard tools and analysis methods were used to measure the water parameters, such as pH, dissolved oxygen (DO), temperature, turbidity, nitrate, phosphate, and ammonia. Gill nets were used to take fish samples that were identified morphologically and measured in terms of diversity using Shannon Wiener (H) and Simpson (1-D) indices. One-way ANOVA with a 95% level of confidence was considered to identify statistical differences between the types of canals. Results: Unlined canals exhibited slightly lower mean pH (7.2 ± 0.1; 95% CI: 7.18–7.22) and temperature (28.3 ± 0.2 °C; 95% CI: 28.28–28.32) but higher DO (6.4 ± 0.1 mg/L; 95% CI: 6.38–6.42), turbidity (11.4 ± 0.1 NTU; 95% CI: 11.38–11.42), and nutrient concentrations (nitrate = 7.0 ± 0.1 mg/L; phosphate = 8.1 ± 0.1 mg/L; ammonia = 5.0 ± 0.1 mg/L) than lined canals. ANOVA results indicated significant differences (e.g., pH: p=0.0003; DO: p=0.0167; turbidity: p=0.0077) in several water quality parameters and fish diversity between the canal types. Conclusions: Unlined canals harbored more ichthyofaunal diversity, probably because of the availability of natural substrates, vegetation, and more stable microhabitats.