Ichthyofaunal survey of rivers within Ewekoro cement manufacturing operational areas

Abstract

A total of 298 fish specimens belonging to seven families were caught during ichthyoplanktonic survey of three rivers within the Ewekoro cement facility catchment area located in southwestern Nigeria. The highest numbers of specimens were caught from Alaguntan (37.0%) and Elebute (36.6%) rivers while 28.9% of the fish samples were collected from Itori River. The fish population and species diversity recorded in the catchment rivers were significantly lower (p < 0.05) than comparative catches from Ewekoro River located about 30 km downstream of the factory operational area. The food items ingested by the specimens across the seasons in the catchment rivers revealed obvious differences in diet with some degree of overlap in the fish trophic preferences. However, the omnivorous species dominated the catches in each of the rivers, irrespective of season. Categorization of the fish specimens based on habitat-related adaptive physiology showed that a significant number of the fish from Alaguntan and Itori Rivers have accessory respiratory organs. The four species with accessory respiratory organs were Polypterus senegalus Curv., Clarias gariepinus C. & V., Ctenopoma kingslayae Gun. and Channa obscura Smith. Of the 12 fish species recorded in the Ewekoro cement facility catchment rivers, only P. senegalus, C. gariepinus, C. obscura and Oreochromis niloticus (Trew.) are valuable food fishes in southwestern Nigeria.

Potential Biological Control of Schistosomiasis by Fishes in the Lower Senegal River Basin

“…For example, African jewel cichlids ( H. bimaculatus ) were moderately common (7.9% relative abundance, Table 1) at our sampling sites but exhibit variable dietary composition and niche breadth depending on the population. This species was almost exclusively piscivorous 74 or insectivorous 67 in some areas but exhibited a more generalized diet largely dependent on algae in another area. 75 With the exception of S. schall , the remaining species with potential for indirect control all had relative abundances ≤ 3%, suggesting minimal snail or schistosome control across the contemporary landscape of the lower Senegal River basin.…”

Element Content of Surface and Underground Water Sources around a Cement Factory Site in Calabar, Nigeria

“…Higher levels of heavy metals have been reported around cement factories compared to unpolluted areas by several studies [2, 6-8, 23, 24]. Emitted dusts are naturally eliminated as deposits to the earth surface through dry or wet deposition in rainfall [25,26]. Cement dust spreads along large area through rain, wind etc., and are accumulated in and on plants, animals, soils and water sources.…”

Levels of selected heavy metals in Synodontis membranaceous Geoffr. in Forcados River, Niger Delta, Nigeria

“…Heavy metal bioaccumulation in the fish could also result from complex processes associated with uptake (Holcombe, Benoit & Leonard, 1979), excretion rates and homeostasis (Du Preez & Steyn, 1992). Variations observed in the levels of heavy metals between the wet and drier months could be attributable to the diluting effects of precipitations during the wet season (Olaleye, 2005). The gill accumulated Cu and other metallic ions probably because of the close proximity between it and external environment as the blood vessels on the gill filament present a large exposed surface area to the water environment (Rehnoldt, Karimian‐Teherani & Altmann, 1976).…”

“…Heavy metal components of crude oils enter into aquatic organisms through the body surface, gills and the gut linings after ingestion of heavy metal tainted materials (Sanders, 1997). Fishes, which have the capability to bioaccumulate heavy metals directly from surrounding water or through food ingestion (Kumara & Mathur, 1991), would therefore be at risk because of the deleterious nature of the surrounding aquatic environment (Olaleye, 2005). This study seeks to establish the level of heavy metal accumulation in Synodontis membranaceous dominant in Forcados River catches.…”