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The inland water fishes of Africa

Didier Paugy
Christian Levêque
Olga Otero

Role of fish in ecosystem functioning

Christian Levêque


The functional relationships between the species in an ecosystem are still poorly understood, but represent one of the main concerns of modern ecology. The role of biological diversity in the functioning of ecological systems is of particular interest. Are all the species found in an ecosystem truly needed to ensure its proper functioning? Do some species have redundant functions, and are there species with more important roles than others (keystone species)? Scientists also wonder about the role of biological diversity in the stability of ecosystems and their capacity to resist or adapt to disturbances, and study the relationships between specific richness and biological productivity.
The answers to these questions are important for the management of aquatic environments and the preservation of biodiversity. But their complexity makes it difficult to propose satisfactory hypotheses. It is nevertheless possible to analyse available data and attempt to find partial answers to the questions raised (Lévêque, 1995b and 1997).

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Impact of fish predation on aquatic communities

Limnologists have long thought that the organization of ecological systems was essentially controlled by the nature and dynamics of the physico-chemical system in which the organisms live. In the standard view of bottom-up control, we look for example at the manner in which environmental factors or the availability of trophic resources influence fish biology and ecology, and the consequences in turn on the organization of fish communities. This deterministic approach regarding communities on the basis of abiotic characteristics remains relevant but needs to be refined. Indeed, several investigations have shown that fishes themselves can have a deciding influence on the ecological functioning of aquatic systems. The hypothesis of top-down control (Northcote, 1988) posits that the effects of predation by fishes cascade down the whole trophic chain and can control the state of the entire ecosystem. A number of studies on African fishes hel...


Research director at IRD. He has published numerous works on the systematics, distribution, and ecology of West African fresh water fishes, and expanded the collections of the MNHN in Paris.

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