The remediation of Hilliards Creek weir with a rock-ramp fishway was undertaken in partnership between Redland City Council and Catchment Solutions. The relic weir on Hilliards Creek was ranked the 36th highest priority fish barrier in Greater Brisbane region. A fish passage options assessment determined that a full width rock- ramp fishway was the best fish passage remediation option for this barrier type in assisting fish to ascend pass the barrier.
|Barrier Ranking||36th in Greater Brisbane region|
|Barrier Type(s)||Surface drop barrier|
|Total Surface Drop||0.75 m|
|Best Remediation Method||Full width rock- ramp fishway|
|Length of Fishway||18 m|
|Number of Ridges||9|
|Drops Between Pools||80 mm|
|Total Construction Time||4 days|
|Total Rock Used||205 t|
|Total Overall Cost||$ 42 000|
Post Remediation Works
Following the construction of the rock- ramp fishway, monitoring was carried out in December 2016 to assess the capabilities of the fishway at passing the full suite of fish species and size classes expected to occur in Hilliards Creek. The fishway trap was set at the exit of the fishway on the upstream side of the crossing, to show the numbers and species of fish that were able to ascend the rock- ramp fishway. Across five days of monitoring, a total of 9 species were surveyed ascending the fishway, at an overall catch rate of 177.66 fish per day. The small size of fish (≥15 mm) that were successful at ascending the fishway indicates the fishway is operating as intended (small size fish are generally weaker swimmers than adults, as they don’t possess the same muscle to propel them through the water). However, the numbers of fish migrating through this fishway were lower than other fishways constructed as part of this project. The lower numbers are due to a low passability fish barrier located downstream in Fellmonger Park (Figure 34).
The Fellmonger Park barrier consists of a raised pedestrian causeway with two small partially blocked pipe culverts buried underneath. This causeway is a major barrier to fish passage during all base, low and medium flow events. Only during very in-frequent ‘drown out’ events is fish passage potentially available past this barrier, but only if migrating fish are located below the weir at the time of ‘drown out’ and possess swimming abilities in-excess of the velocities experienced at the barrier site.
Boat electrofishing surveys were undertaken upstream and downstream of this barrier to detect any differences in fish community condition. The survey results demonstrated the barrier was significantly impacting upstream fish communities, with the catch rate (56.97 fish/min) of diadromous fish species downstream of the barrier more than four times higher than upstream of the barrier (12.37 fish/min) (Moore, 2017).
Table 1a. Showing fish species, size range and catch per unit effort of fish (fish/day) successful at ascending the fishway
|Migration Classification||Common Name||Species Name||Size Range
|Diadromous||Empire gudgeon||Hypseleotris compressa||19- 81||18.22|
|Long-finned eel||Anguilla reinhardtii||60- 800||1.08|
|Sea mullet||Mugil cephalus||38- 51||15.62|
|Striped gudgeon||Gobiomorphus australis||38- 51||1.3|
|Potamodromous||Hypseleotris species||Hypseleotris sp.||20- 43||77.44|
|Unspecked hardyhead||Craterocephalus fulvus||20- 71||54.66|
|Pest Fish||Mosquito fish||Gambusia holbrooki||15- 35||8.68|
|Total Species and Overall CPUE||9||177.66|