Aspects of the ecology of Nigeria Fresh Waters: A case study on Physicochemical characteristics Plankton and Finfish from Lower Sombreiro River in Niger Delta

This paper is aimed at baseline information on the fisheries status of the fresh water reaches of somberiro river in the Niger Delta; while highlighting the challenges of obtaining fisheries data in the waters of the Niger Delta. Both physico-chemical and plankton were analyzed using standard methods Plankton and fish species were identified using monographs, descriptions, checklists and keys. The mean values temperature, pH, conductivity, turbidity, salinity, dissolved oxygen, total dissolved solids, dept, flow rate and rainfall were: 27.1 ± 0.09 (°C), 6.50 ±0.05, 4515.3±656.67 (μscm^-1), 1.8±.09 (ntu), 3.1±0.45(0/00), 7.10±0.06 (mg/l), 673.27±97.34(mg/l), 6.23±0.22(m), 0.19±0.39(m/s) and 184.1±19.89(mm) respectively. A total of 43 species from 5 taxonomic groups were recorded). The species with the highest number was Melosira granulata (357) with 5.2%, while the least number was for Stephanodiscus asroea (47) with 0.7%. Bacillariophyceae was the highest (50.3%), Chlorophyceae, 24.8%; Cyanophyceae, 15.4%; Xantophyceae, 7.2%; and Chrysophyceae, 2.5%. A total of 17 zooplankton species from 6 taxonomic groups were present. The species with the highest number (248) was Paracyclops fimbriatus, with 12.1%, while Mysis sp. had the lowest number (25) with 1.2%. The family Copepoda had the highest (45.5%), Cladocera, 23.4%; Euphaucea, 10.3%; Protozoa, 11.9%; Rotifera, 7.8%; and Decapod Crustaceae, 1.2% (the least). The family Copepoda had the highest (45.5%), Cladocera, 23.4%; Euphaucea, 10.3%; Protozoa, 11.9%; Rotifera, 7.8%; and Decapod Crustaceae, 1.2% (the least). A total of 72 finfish species from 38 families were present. Brienomyrus branchystius was the species with the highest number (412) accounting for 5.9% of total fish caught. No particular specie was dominant, Breinomyrus branchystius and B. longianalis were aboundant, Erpeptiochthys calabaricus and Chromidotilapia guentheri were common; while the rest were either rare or few. Analysis of variance (ANOVA) was carried out on finfish and plankton collected from the different stations and seasons. The Duncan’s Multiple Range Test was used to determine significance in mean catches and estimates. Correlation analysis of the water parameters and finfish catch was done. Phytoplankton collected had a negative correlation with dissolved oxygen and pH. However, it correlated positively with flow rate. The correlation between zooplankton collected and turbidity was negative. The percentage total catch increased with higher conductivity values, increased total dissolved solids, reduced turbidity and rainfall, and relatively faster flow rates. However, it declined with reduced conductivity, total dissolved solids, relatively slower flow rates, increased turbidity, and rainfall. Finfish catch correlated positively with conductivity and total dissolved solids. The physicochemical characteristics, plankton and finfish species of the lower Sombreiro River in the Niger Delta, correlates the relationship between the biotic and abiotic parameters for the management of similar water bodies for regional, national and international fisheries development.