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

Sequential fishways reconnect a coastal river (#54)

Meaghan L Duncan 1 , Wayne Robinson 2 , Jonathon Doyle 1 , Jason Thiem 1 , Lee Baumgartner 2
  1. NSW DPI Fisheries, Narrandera, ENGLISH, Australia
  2. Charles Sturt University, Albury, NSW, Australia

River regulation infrastructure has been implicated in worldwide aquatic biodiversity loss. Instream barriers such as weirs prevent fish migration and the impact can be particularly severe for diadromous species. Fishways are frequently installed on in-stream barriers to reconnect migratory pathways and rehabilitate diadromous populations. We monitored a coastal fish community’s response to fish passage restoration at ten predominantly low-level weirs in the lowland reaches of the Nepean River in south-eastern Australia. Pre-fishways, there was a gradient of reduced species diversity in an upstream direction including the absence of many diadromous species, despite the regular inundation frequency of most weirs. Post-fishways, species diversity was still greater in the downstream monitoring sites; however, there was evidence of a positive change in fish community structure from upstream sites. Most notably, three diadromous species rapidly expanded their distribution upstream and one amphidromous species expanded its downstream distribution. This study demonstrates appropriately designed successive fishways can successfully reconnect river systems for an entire fish community, encompassing species with a broad range of swimming abilities and diverse life histories.