The distribution and feeding ecology of the characid Brycinus sadleri in Lake Nabugabo, Uganda: implications for persistence with Nile perch (Lates niloticus)

Abstract

Coincident with a rapid increase in
numbers of introduced predatory Nile perch (Lates niloticus) in lakes
Victoria, Kyoga, and Nabugabo of ast Africa was a dramatic decline in
populations of many native fishes. However, a few species, including the
characid Brycinus sadleri, have shown remarkable resilience. This study
examined how the distribution and foraging behaviour of B. sadleri in
Lake Nabugabo may facilitate their persistence with Nile perch. Both B.
sadleri and Nile perch were most abundant in exposed areas offshore (20m)
as opposed to wetland areas. However, we found evidence for a strong diel shift
in activity and modest changes in the habitat use of B. sadleri that may
contribute to persistence with Nile perch. In general, B. sadleri
actively foraged during the daylight hours and remained quiet during the night.
Nile perch began foraging during the early evening and were more active during
the night than during the day. By early morning the proportion of full stomachs
in Nile perch was low, though there was evidence of a low level of feeding
activity during the day. Stomach contents of Brycinus sadleri indicated
a shift from surface to benthic feeding as light levels increased, which
appears to decrease their susceptibility to predation by Nile perch during the
daylight hours.



African Journal of Aquatic Science
2004, 29(1): 13–23