A study on the macroinvertebrate fauna of lower Ogun River at Ishasi, Ogun state, south-west Nigeria
The composition, distribution and abundance of macroinvertebrate fauna of Lower Ogun River were studied at Ishasi from January 2006 to December 2007. Bank-root macroinvertebrates were sampled using kick sampling and scooping gear while Ekman grab were used to sample the mid-channel from three stations with 200m intervals on monthly basis. Physico-chemical parameters were also measured and found to be within the ranges suitable for normal aquatic life. A total of 27,005 macroinvertebrate individuals from forty-five taxa were collected from the entire study area (pooled data of the three stations). Three Macrobrachium species dominated the macroinvertebrate fauna. Class Insecta had the highest number of representations with thirty-three taxa cutting across eight orders including the pollution sensitive/clean water ones (Odonata, Trichoptera, Plecoptera and Ephemenoptera). Margalef species richness and Shanon-Wiener diversity indices levels of 4.41 and 1.18 respectively were recorded from the study area. The three sampling stations had insignificantly different physico-chemical parameters, macroinvertebrate abundance and diversity levels (p>0.05), which indicate uniform ecological conditions within the study area. The findings indicate a relatively stress free environmental condition within the study area.
Key words: Macroinvertebrates, Physico-chemical parameters, Species composition, Diversity, Abundance.