Some observations on fish-consumable insects of Ossiomo River, Nigeria

Abstract

The fish-consumable insect fauna and some physico-chemical conditions of the Ossiomo River at Ikpe in Edo State, southern Nigeria were investigated between January and June 2002. The mean water temperature was 26.0°C, while alkalinity, conductivity and dissolved oxygen had mean values of 41.3mg/l, 60.6µS/cm and 3.40 mg/l respectively. The Biochemical Oxygen Demand (BOD₅) was low (1.46mg/l) and the pH was slightly acidic (6.31). The mean nutrient values were low (0.36mg/l NO₃ and 0.44mg/l PO₄). Fifteen taxa represented by hundred and thirty eight individuals were recorded. Ephemeroptera (48.55%) represented mainly by Centroptilum (21.74%) and Diptera (44.93%) represented mainly by Pentaneura nilotica Kieffer (31.88%) were dominant. The subdominant taxa were Baetis tricaudatus Dodds (12.32%), Cloeon cylindroculum Kimmins (8.70%) and Pseudocloeon (5.80%). The indices of diversity, Margalef's taxa richness (D) and Shannon Diversity (H¹) were higher in the more vegetated and shaded station 1 (2.72 and 2.14 respectively) than in station 2 (1.74 and 1.67 respectively) in the station 2. The two stations were homogeneous as no significant differences (P>0.05) were observed in terms of faunal abundance and Shannon diversity.

Keywords: aquatic insects, fish food, water quality, southern Nigeria

Tropical Freshwater Biology 2003/2004 Vol. 12/13: 25-33