Filming and snorkelling as visual techniques to survey fauna in difficult to access tropical rainforest streams

Abstract

Dense tropical rainforest, waterfalls and shallow riffle-run-pool sequences pose challenges for researcher access to remote reaches of streams for surveying aquatic fauna, particularly when using capture-based collecting techniques (e.g. trapping, backpack and boat electrofishing). We compared the detection of aquatic species (vertebrates and invertebrates >1cm in body length) within pool habitats of a rainforest stream obtained by two visual techniques during both the wet and dry season: active visual survey by snorkelling and baited remote underwater video stations (BRUVSs). Snorkelling detected more species than a single BRUVS at each site, both within and among seasons. Snorkelling was most effective for recording the presence and abundance of diurnally active small-bodied species (adult size <150mm total length), although both techniques were comparable in detecting large-bodied taxa (turtles, fish and eels). On the current evidence, snorkelling provides the most sensitive and rapid visual technique for detecting rainforest stream fauna. However, in stream sections dangerous to human observers (e.g. inhabited by crocodiles, entanglement, extreme flows), we recommend a stratified deployment of multiple BRUVSs across a range of stream microhabitats within each site.