Integration Of Scales, Indices And Environmental Gradients In The Evaluation Of The Conservation Of Rivers Of The Eastern Coast Of Lake Maracaibo, Venezuela

The drainages of the eastern coast of Lake Maracaibo of Venezuela are subjected to strong disturbances, especially the loss of riparian forests and transformation of riverbeds, with detrimental effect on river ecosystems, but their conservation status is unknown, limiting appropriate management of regional hydrobiological resources. In the tributary rivers Machango and Misoa, 16 drainage sites were evaluated by characterizing the channel dimensions, the substrate composition and the water physicochemical variables. Aquatic insects were also collected using standardized sampling. The conservation status of the sites was estimated using environmental indices (IHF: fluvial habitat index; QBR-And: index of quality of Andean riparian forest; HIP habitat integrity index). Relationships between habitat gradient and the indices were explored by multivariate classification and ordination analysis. The synthetic variables generated were related environmental indices and biotas. The aquatic habitat showed a heterogeneity gradient directly and significantly associated with the variables that determine the structure of the channel and riparian zones. All indices scored higher where there was more vegetation cover in riparian zones and heterogeneous substrates; also, the indices had significant correlations with the gradient of fluvial habitat and number of insect families. A gradient in the conservation status was detected, where a class of low conservation was associated with homogeneous and impacted habitats and the lowest richness of insect families. The indices used are suitable to estimate conservation classes of rivers and their biotas, and may be employed for monitoring drainages.