As part of an assessment of fishway efficiencies, Mackau Regional Council commissioned Catchment Solutions to undertake fish sampling in two drainage systems.
The objective of the Forbes Road fishway sampling was to validate the performance of an established fishway, while the Blackrock Creek survey was to form a baseline fish community record to establish preliminary data prior to the installation of a fishway on the Old Bowen Road causeway. In addition, comparisons in species composition and population structure at the Old Bowen Road provided an indication of the current impacts caused by the road crossing.
Fishway performance sampling was conducted at the Forbes Road causeway on the O’Connell River, above and below the causeway, by utilising cone traps. Sampling results confirmed the fishway was successful at passing both juvenile and adult fish, including bottom and surface dwelling species.
Fish community sampling was also conducted at four sites within Blackrock Creek using electrofishing techniques.. In total 1103 individual fish (16 species) were recorded.
In the Mackay region, the impact of barriers such as causeways, road crossings, weirs, and dams on fish passage has been identified as a major cause of the reduction of native fish populations and community assemblages .
Most native fish species do not have the ability to move over large barriers or vertical inclines. Remediating large barriers to enhance fish passage through the construction of fishways is a vitally important rehabilitation strategy essential for maintaining not only healthy fish communities, but the entire aquatic ecosystem.
The installation of fishways is one remediation option that can improve connectivity between fragmented sites. Fishways are designed to reduce the surface drop and water velocities caused by the barrier, creating conditions that fish are able to negotiate.
The trapping operations demonstrated that the fishway at Forbes Road was successful at passing small fish (<150 mm) during low flow conditions. It is anticipated the fishway will also be successful at passing both small and large fish in moderate flow conditions.
Many of the potadroumous species recorded in Blackrock Creek were also recorded during fishway sampling at Forbes Road on the O’Connell River. This suggests that a fishway on the Old Bowen Road would facilitate increased fish passage during similar flow conditions and that improved fish passage would also be likely during moderate flow conditions as well.