Rivers and wetlands of Australia’s eastern tropics have been heavily impacted by decades of land-use change. Many fish species migrate within freshwater environments, or between fresh and saltwater systems to feed and spawn, yet their capacity to migrate has been diminished through changes to habitat, water quality and physical barriers to fish passage. There are thousands of constructed barriers to fish passage in Australia’s north-eastern tropics and these include pipes and culverts, urban drains, earthen bunds, causeways, weirs and irrigation infrastructure. The net effect of these changes on the productivity of fish stocks is largely unquantified for many catchments but is likely to be substantial.
Fishways are increasingly being constructed in the Australian tropics to improve the capacity for fish migration and to increase the extent of available habitat, yet there is limited data on their efficacy in tropical river systems. Here, we present results from two seasons of fish monitoring in the wet and dry tropics of north-east Queensland. We discuss our findings in the context of contemporary habitat quality and condition, and factors contributing to differences observed within and between catchments.