Occurrence of Orthetrum abbotti Calvert (1892) (Odonata, Libellulidae) and intraguild predation on Clarias gareipinus Burchell, 1822 (Suliformes, Clariidae) and Oreochromis niloticus L., 1758 (Perciformes, Cichlidae) fry in Lagos fish farms

Intraguild predation occurs when species competing for the same resource prey upon or parasitize one another. This may result in economic losses under commercial circumstances. A survey of the insect species of fish farms in Badagry and Ojo Areas of Lagos State, Nigeria was carried out followed by an evaluation of the predatory ability of Orthetrum abbotti nymphs on fish fry. Nymph predation was evaluated in the laboratory against fry of Clarias gariepinus and Oreochromis niloticus. Samples of insects were randomly collected from 10 earthen ponds, 10 concrete ponds and the vegetation surrounding the ponds and identified over a period of 12 weeks from three study fish farms. Six species of insects belonging to four orders namely Notonecta unifasciata, Gerris remigis, O. abbotti, Aedes aegypti, Dysticus marginalis and Acentria ephemerella syn. niveus were collected from the ponds. Studies on feeding preference of 5th nymphal instar of O. abbotti on fry of C. gariepinus and O.  niloticus over other food types revealed  that the dragonfly preferred to feed more on C. gariepinus fry than on O. niloticus although there was no significant difference in the number of O. niloticus and C. gariepinus fry preyed upon by O. abbotti nymphs.