Trophic Ecology of Sardinella gibbosa (Pisces: Clupeidae) and Atherinomorous lacunosus (Pisces: Atherinidae) in Mtwapa Creek and Wasini Channel, Kenya

Abstract

The food habits of two schooling planktivorous fishes, Sardinella gibbosa and Atherinomorous lacunosus, were investigated in Mtwapa creek and Wasini Channel of the Kenya coast. Spatial and temporal variations in their food and feeding habits were assessed using the percentage numerical abundance method, percentage frequency of occurrence, stomach fullness indices and the Tokeshi graphical method. This study established a clear spatial separation of Mtwapa creek from Wasini Channel in terms of the abiotic and biotic data. Highly significant differences (t-test, p < 0.05) were observed between the two study areas in temperature, salinity, transparency, conductivity, chlorophyll a and in zooplankton abundance and diversity. The diet of the two fish species showed clear spatial and temporal differences, which were dependent on habitat variability. The two species belong to the omnivorous trophic category. Sardinella gibbosa from both sites fed mostly on copepods during the two seasons. Atherinomorous lacunosus fed mostly on phytoplankton, copepods and nematodes during the NE Monsoon. However, its diet was dominated by nematodes during the SE Monsoon. Overall, both fish species exhibited generalised and opportunistic feeding habits. Their diet was influenced by changes in the quality and quantity of food in the environment and the fishes migratory patterns.