There are thousands of barriers to fish passage in Australia’s north-eastern tropics. Together with habitat degradation and water quality issues, these barriers to migration are fragmenting aquatic habitats and constraining the productivity of fish populations. The impact of these waterway barriers on fish stocks is pronounced where barriers exist at the freshwater-saltwater interface, particularly in regions such as north-eastern tropical Australia where a high proportion of fish species migrate between fresh and saltwater. Fish barrier remediation has increased in recent years, however remediation work in tropical Australia is often completed due to capital works that trigger State government legislation, rather than any broad-scale commitment to improving fish migration. As such, many barriers that have been listed as high priority for remediation remain in place due to lack of funding. In some cases where fish passage remediation has been undertaken, functionality of these structures may be compromised, yet building new fishways is often prioritised over repairing existing structures.
Here, we present case studies from fish monitoring work undertaken in the wet and dry tropics of north-east Queensland. Monitoring was completed at fishways, tidal gates, bund walls and culverts in agricultural and urban environments. We discuss our findings in the context of contemporary habitat quality and condition, and of range contractions that many fish species experience. We discuss contemporary challenges to effective monitoring and the increasing role of environmental stewardship in fish passage science. We also discuss the need for long-term monitoring to inform fish passage remediation work, to identify where repair or maintenance of existing structures is needed and to inform the need for further habitat improvement actions.