Spatial and circadian variation of aquatic insect communities in three tropical fish ponds (Natiokobadara, Korhogo, Northern Côte d’Ivoire)

We analysed aquatic insect distribution and their circadian variation in tropical fish ponds in a piscicultural farm
used for Nile tilapia (Oreochromis niloticus) culture near Natiokobadara locality  in the Northern Côte d’Ivoire. Among  ponds  of  this  farm,  three  were  selected:  a  pond  (D4)  without  fish,  a  pond  (A3)  stocking  with  7500 fingerlings and pond (T12) of reproducers containing 680 parents.  In each pond, aquatic insect samplings were undertaken every 04 hours during 24 hours in the three selected fish ponds during two cycles. Besides, ordinary samplings were done during the sampling period (July-August 2001). Overall, 25 taxa belonging to 15 families and  seven  orders  were  recorded.  The  pond  without  fish  (D4)  contained  the  higher  aquatic  insect  richness. Heteropterans  and  dipterans  were  the  mostly  abundant  and  diverse  groups.  Their  predominance  was  due  to respectively Anisops sardea  and Chaoborus anomalus. According the circadian variation of these two main taxa, it  is  likely  that  assemblages  of  these  two  main  taxa  are  rather  shaped  by  biotic  factors  such  competition.  The circadian variation of all aquatic insects collected showed that the maximum of insects was registered in daytime in the pond without fish (D4) whereas in the two others ponds (A3, T12) containing fishes the highest abundance of  insects  was  obtained  during  night.  The  risk-of-predation  hypothesis  implies  aquatic  insects  in  ponds containing fish exhibit predominately during night