TEMPORAL PATTERNS OF RESOURCE PARTITIONING AMONG CICHLA SPECIES IN A VENEZUELAN BLACKWATER RIVER

In channel and floodplain habitats of the Cinaruco River, Venezuela, C ichla temensis was more abundant and larger than C. intermedia and C. orinocensis. Seasonal variation in hydrology influenced habitat use, s pawning, and predator-prey interactions. The three piscivores partitio ned habitat, with C. intermedia showing a strong affinity for structur ed habitats in the main channel during all water level fluctuations. C . orinocensis was most abundant in shallow areas with submerged struct ure in lagoons and, to a lesser extent, in low velocity regions of the channel, and C. temensis occupied a wide range of lotic and lentic ha bitats. During the low-water period, the feeding frequency and body co ndition of all three species declined, and this was related, in part, to preparation for spawning near the end of the low-water season. The diet of C. intermedia was least similar to its two congeners during fa lling and rising water. C. orinocensis and C. temensis had lowest diet overlap during the low-water conditions, the period when many individ uals of these two species move into lagoons for nesting. Prey in stoma chs were significantly larger during the falling-water than the rising -water period, and predation by Cichla and other large piscivores duri ng the falling-water period may have reduced the abundance of large pr ey, particularly Semaprochilodus kneri. These migratory detritivorous fish were important prey for C. temensis during the falling-water peri od and probably contributed a substantial fraction of the annual energ y intake for this species. Together, the three Cichla species consume a wide spectrum of prey from a diverse fish assemblage, but prey are s ubdivided based on habitat, prey type, and season. (C) 1997 The Fisher ies society of the British Isles.