Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Improving fish swimming performance through the provision of roughened channel beds: implications for culvert remediation efforts in Australian waterways (#40)

Rebecca L Cramp 1 , Caroline Thompson 1 , Harriet R Goodrich 1 , Micah Rayburn 1 , Essie Rodgers 1 , Brianna Heaslip 1 , Jabin R Watson 1 , Matthew A Gordos 2 , Craig E Franklin 1
  1. The University of Queensland, St Lucia, QUEENSLAND, Australia
  2. Department of Primary Industries – Fisheries, Wollongbar, NSW, Australia

Culverts act as hydrological barriers to fish movement by severely altering the hydrodynamic conditions within the channel environment. The widespread use of culverts has caused significant declines in freshwater fish populations worldwide. To address this issue, culvert remediation through the provision of naturalistic substrates to induce bed roughening, has proved effective at increasing the likelihood of fish passage in a variety of European and North American fish species. Whether culvert roughening is similarly efficacious for small bodied Australian fishes and the physiological basis for why roughening might be beneficial to fish, are largely unknown. Here, we found that in most cases, the provision of a roughened bed substrate generally improved swimming performance by reducing the metabolic cost of swimming in seven out of nine Australian fish species examined, however the relative impact of different bed roughness designs (i.e. relative size of rocks and their spacing), differed across species. However, one species was detrimentally affected and one gleaned no benefit from the provision of a roughened substrate environment, suggesting that not all species may benefit from this type of culvert remediation. Traversable culvert modelling suggests that substrate roughening would increase the likelihood of successful passage, with many species capable of swimming at higher bulk velocities in the presence of a roughened culvert bed. Our data show that culvert bed roughening can improve swimming performance in many small-bodied Australian fish, indicating that this is likely to be an effective remediation strategy to improve passage of native fish through culverts. But because not all species may benefit equally from bed roughening, we need to understand species-specific hydrodynamic requirements to inform tailored, context-specific, remediation approaches.