Assessment of the water quality and Odonata assemblages in three waterbodies in Ilara-Mokin, south-western Nigeria

Abstract

This study investigated the biological water quality and Odonata assemblages in three waterbodies in Ilara-Mokin, with the aim of determining the ecological integrity of the ecosystems. Sampling of Odonata specimens was carried out over April–August, 2017 between 9.00am and 4.00pm under favourable conditions. Some physico-chemical parameters of the water such as dissolved oxygen, electrical conductivity, temperature, flow rate, pH, and water depth were also investigated. A total of 41 odonate species were recorded in this study and this was represented by 29 dragonfly and 12 damselfly species. These species are contained in seven families (Macromiidae, Gomphidae, Libellulidae, Calopterygidae, Coenagrionidae, Chlorocyphidae and Platycnemididae). The seven families were recorded at Aponmu River while Omifunfun River and Isokun River accounted for six and four families respectively. However, the highest number of individuals was collected at Isokun River. Libellulidae was the dominant family. Diversity indices revealed that Aponmu river was the richest in terms of species richness, diversity and taxa distribution (Shannon: 3.18, Simpson D: 0.95, Margalef: 7.38, evenness: 7.38, equitability: 0.93). Dragonfly Biotic Index (DBI) analysis indicated that Omifunfun River represented the best habitat condition in the study area while Isokun River was considered the most perturbed sampled site in the study area. Conservative efforts should be intensified to protect Omifunfun River in order to preserve all extant aquatic biota and other available resources therein.