Effects of selected heavy metals on morphology of Oreochromis niloticus and Clarias gariepinus along Ruiru River, Kenya

Abstract

Abstract. Ouma KO, Otieno SA, Sharma RR 2019. Effects of selected heavy metals on morphology of Oreochromis niloticus and Clarias gariepinus along Ruiru River, Kenya. Bonorowo Wetlands 9: 92-107. The objective of this study was to determine the levels of heavy metals in tilapia and catfish species along the Ruiru River. Sediments, water, and fish samples were collected using systematic random sampling techniques. Three sites were established downstream of the river, 1000 meters from Ruiru Town. The other three were established upstream of the river, 1000 meters from Ruiru Town. Fish samples were transported to the National Museums of Kenya laboratory for identification. An atomic absorption spectrophotometer was used to examine metals. Fish gills and livers were also examined for histopathological changes. Using one-way analysis of variance, researchers analyzed data on heavy metal levels in the water, sediments, fish gills, livers, and muscles. Correlation coefficients were also calculated to assess the relationship between fish length and weight and metal concentrations in fish liver, gills, and muscles and between levels of heavy metals in water and sediments. In April, 0.167±0.014 mg/L, August, 0.054±0.003 mg/L, and December, 0.222±0.101 mg/L (F = 2.10, p = 0.202), mean chromium levels in water were not statistically significant, but were statistically significant at the downstream sites 0.236±0.019 mg/L, 0.058±0.001 mg/L, and 0.222±0.101 mg/L during the three months (F = 125.63, p<0.001). Significant positive correlations between the levels of iron in sediments and water were found at both upstream and downstream sites, with r = 0.7319, p = 0.025, and r = 0.8506, p = 0.0037, respectively. The linkage between lead levels in sediments and water at upstream sites was not significant (r = 0.343, p = 0.366), while it was significant (r = 0.7523, p = 0.019) at downstream sites. Chromium levels in sediments and water at upstream sites indicated a positive but non-significant connection (r=0.5339, p=0.138). There was a substantial positive correlation between chromium levels in sediments and water (r = 0.9787, p<0.001). Metals accumulated in fish tissues in the following order: liver>gills>muscle, and Clarias gariepinus tissues from downstream sites exhibited higher amounts of metals than Oreochromis niloticus tissues from the same sites. Both kinds of fish exhibited higher iron levels than lead in all tissues, with chromium being the lowest. The liver and gills of fish from the upstream research sites had normal features on histology. Hepatocytes with larger nuclei were found in fish livers from downstream sites. The secondary lamellae of the gills had degenerated and fused. According to the study, metal levels in sediments were greater than in water. Fish from the downstream sites also showed morphological alterations in the liver and gills. The study's findings suggest that people who eat such fish may be exposed to metal poisoning. According to the report, the National Environment Management Authority should implement measures to reduce industrial trash flow into the Ruiru River.