Oral Presentation Australian Society for Fish Biology Conference 2017

Assessing the impact of macrophyte density on underwater video camera monitoring of fishes in tropical wetlands (#132)

Bryan Baker 1 , Alison King 1 , David Crook 1 , Brett Murphy 1 , Lisa Chandler 2 , Mark Ellis 2
  1. Charles Darwin University, Casuarina, NT, Australia
  2. Department of the Environment and Energy, Supervising Scientist Branch, Darwin, NT

Underwater video cameras are being increasingly used in freshwater environments to sample and monitor aquatic biota. Northern Australia has vast areas of unmodified freshwater habitats containing a large diversity of freshwater fishes. However, fish surveys in the region have been limited, as sampling in many of these habitats is inherently difficult, with challenging environmental conditions, remoteness, complexity of habitat, and safety issues including large predators.

Pop-net surveys have been used to monitor freshwater fishes in shallow vegetated billabongs around the Ranger uranium mine in Kakadu National Park for many years. However, this survey technique presents a human safety risk due to crocodile attack, and additional safety measures (such as barrier netting and crocodile spotters) can disturb habitats, affect catch rates, and lead to higher field costs. Underwater video cameras have been proposed as a viable alternative, however, dense macrophytes can impede visibility.

This study investigated the impact of macrophyte density on video surveys. We deployed cameras in three shallow billabongs that contained varying densities of macrophytes, and sampled fish assemblages using both video cameras and pop nets. Macrophyte density was also measured in each sampling location. This study constitutes a component of a larger project investigating the utility of underwater video cameras for monitoring freshwater fishes in wetlands of northern Australia, and will assist in the future utilisation of underwater video cameras for monitoring and research in the region.