The Cichlid Fishes of Lake Malawi, Africa

Abstract of Doctoral Dissertation

Emidio Raul Andre
University of Waterloo, Ontario (Canada), 2000
Advisers: Hamish Duthie & Robert Hecky  

Benthic nutrient cycling: The role of fish in nitrogen and phosphorus regeneration in the rocky littoral zone of Lake Malawi/Nyasa/Niassa, Africa  

The interaction between the cichlid fishes of the nearshore rocky littoral zone of Lake Malawi with the epilithic periphyton community is addressed in this study, looking specifically at fish grazing rates and importance of the fish community in recycling of nitrogen and phosphorus through excretion, defecation and mortality.

To determine rates of nitrogen and phosphorus regeneration through excretion and defecation, a series of in situ fish incubations in 13L plexiglas chambers were performed at two islands of Lake Malawi. Fish grazing rates were assessed by determination of fish consumption rates using Kraft's (1992) bioenergetics model where defecation and excretion rates were derived from the in situ experiments and growth rates were determined in the lab by rearing 30 fish specimens for 22 days under controlled conditions. Mortality was assessed by the assumption that it is equal to growth as fishing is negligible and there is no long-term fish biomass change in the nearshore rocky littoral zone of Lake Malawi. [Abbreviated abstract]




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