In June 2019, the fish passage at the Clews Road causeway in upper Murray Creek, Mackay, was rehabilitated through the construction of a 10-ridge rock-ramp fishway.
Mackay Regional Council undertook a full refurbishment of the entire causeway and as part of these works, incorporated and funded the fish ladder at the site which was constructed by Catchment Solutions. The former causeway presented a surface headloss of approximately 700mm between the upstream and downstream reaches of the creek. This barrier was preventing access to a significant portion of the upper catchment to a range of important diadromous species including Jungle perch and barramundi.
Figure 1. The Clews Road causeway fish barrier, showing 700mm drop between upstream reaches (left) and downstream reaches (right) in Murray Creek, Mackay.
The fishway is comprised of 10 ridges and pools, with 75mm drops between each pool, and fishway pools spaced 2m apart. The fishway functions through fish approaching from downstream and using their burst speed to ascend the fishway ridge slots, before utilising slack water resting zones in the pools to regain their energy before ascending the next ridge. Importantly, the rock-ramp fishway design maintains consistent flow through each ridge slot, and deep pools which dissipate this flow energy. These features are critical in ensuring the young-of-year recruits of diadromous species such as mangrove jack, sea mullet, long-finned eel elvers, jungle perch and barramundi which are poor swimmers, are able to negotiate the fishway and reach upstream habitats.
Importantly, this catchment is one of the few systems in the area recognised as supporting a small jungle perch population. Relatively few isolated populations of the species persist in Mackay, primarily due to;
• barriers fragmenting their habitat and impacting their catadromous, migratory life-cycle,
• habitat loss; especially in-stream woody debris and riparian vegetation which supplies their predominantly terrestrial diet, and
• poor water quality and sedimentation.
The remediation of the Clews Road barrier through the construction of a rock-ramp fishway is a significant step in facilitating the recovery of the species, allowing juvenile recruits to reach upper catchment headwater streams where they grow to maturity. It is hoped continued remediation works addressing fish passage barriers, along with habitat and water quality improvement works, can facilitate the re-establishment of jungle perch populations throughout Mackay.
Figure 2. Left; Commencement of fishway construction, with first wall and ridge rocks in place and right; side-view showing fishway walls nearing completion.
Figure 3. Left; Fishway completed and being prepared for concreting and right; concrete pump securing fishway in place through the use of fibre-reinforced concrete.
Figure 4. Left; Completed fishway after being opened following concreting and right; standing on upstream bank showing fishway and causeway scour protection secured in place.
Figure 5. Causeway and fishway at the completion of project.