Diet-shifts and food-dependent survival in Engraulicypris sardella (Cyprinidae) larvae from Lake Malawi, Africa

The diet of Engraulicypris sardella (Cyprinidae) larvae was determined from the open waters of Lake Malawi, Africa. The guts of first-feeding larvae of 2-3 mm total length (TL) usually contained many cells of 5-9 mu m diameter tentatively identified as a non-colonial green alga (Chlorophyta). The number of these cells in the guts of larvae declined as larvae increased in size, and were not found in larvae greater than 9 mm TL. Other types of phytoplankton were rarely seen in the guts of larvae. Copepod nauplii were eaten by larvae greater than 4 mm TL, and copepodite copepods and cladoceans by larvae greater than 5 mm TL. The biomass of open water crustacean zooplankton and E.sardella larvae were determined over a 2-year sampling programme. The mortality rate of E. sardella was negatively correlated with zooplankton biomass, but was not significantly correlated with the amount of zooplankton food in the guts of larvae.