Drift and settlement of stream insects in a complex hydraulic environment

Abstract

The hydraulic and geomorphic characteristics of stream patches are often associated with distinctive assemblages or densities of stream invertebrates, and it is routinely presumed that these patterns reflect primarily species-specific habitat requirements. An alternative hypothesis is that such patterns may be influenced by constraints on movement, such as the results of departure and settlement processes. We describe a manipulative experiment that examined how the hydraulic environments created by topographic bedforms influenced the drift behaviour and potential settlement sites for two species of mayfly (Baetis rhodani and Ecdyonurus torrentis). These species are common in the drift and of..