There are thousands of barriers to fish passage in Australia’s north-eastern tropics. Together with habitat degradation, these barriers to migration are fragmenting aquatic habitats and constraining the productivity of fish populations. The overall decline in ecosystem services in highly impacted tropical waterways is difficult to quantify, however the abundance and diversity of many fish populations are likely far below pre-European levels. Fish barrier remediation has increased in recent years, however the impetus to undertake remediation work in tropical Australia is often due to capital works that trigger State government legislation, rather than any broad-scale commitment to improving fish migration. There are also challenges to assessing the efficacy of fishways in tropical river systems, including swift, turbid water and the presence of estuarine crocodiles.
Here, we present results from five seasons of fishway monitoring work 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. We discuss contemporary challenges to effective monitoring and the increasing role of environmental stewardship in fish passage science.