Temporal dynamics of Chaoborus larvae (Diptera : Chaoboridae) in the tropical ecosystem (lake Ayamé I ; Côte d’Ivoire).

Abstract

Chaoborus larvae are voracious predators of zooplankton able to change their specific composition and size structure. Thus they appear as competitors of fish. They also represent food for planktophage fish. The temporal dynamics of Chaoborus larvae was studied (from january to october 1997) in the fishery of Bakro (5°33’N and 3°15’W) situated in lake Ayamé I (Côte d’Ivoire). Two peaks of density were observed : the most pronouced in March (end of the major dry season) with 747 ind./m2, and another, less pronouced in June (end of the major rainy season), with 280 ind./m2. Differences between densities may well be explained by the advent of the rainy season which leads to a decline in trophic resources (zooplankton) and exposes Chaoborus larvae to predation by fish.

Key-words : Chaoborus larvae, Dynamics, lake Ayamé I, Côte d’Ivoire,West Africa.