Project Catalyst was invited to speak at the Australian Water Association’s Queensland state conference on the Sunshine Coast in November 2020.
Ross Neivandt from Catchment Solutions presented a 20 minute overview and conference paper that outlined the achievements and activities of Project Catalyst. The project received many compliments for the outstanding work it does in improving farming and environmental outcomes.”
Catchment Solutions has successfully completed on-ground works at the Collinsdale erosion remediation project site. The primary erosion remediation site is located at the Collinsdale Station, which is situated on the southern side of the Fitzroy River, in Garnant, approximately 30km from Rockhampton. The 450ha cattle property is situated within the Louisa Creek catchment and has been identified through Paddock to Reef modelling as contributing the 10th highest load of sediment to the Great Barrier Reef Marine Park from the Fitzroy basin area.
The Reef Trust IV Erosion Remediation project area included the rehabilitation of large-scale gully erosion, using earthworks to reshape and fill the erosion scar, with the project, including;
Figure 1. Before and after images taken from a drone of the primary project site, showing significant gully erosion in pre-construction image and cut, fill and reshaping earthworks in post-construction image.
With the completion of earthworks in late 2019, the site has been irrigated, seeded, mulched and revegetated to reduce rainfall impacts on the rehabilitated gully area.
Over eight kilometres of fencing has been installed along Louisa Creek to allow natural regeneration of the riparian vegetation and over 8 additional watering points (troughs and piping) have been installed to allow alternative water supply and reduce grazing pressure on the lower catchment of Louisa Creek. An additional 4 kilometres of fencing has also been installed to protect the rehabilitated sites and to improve rotational grazing practices.
Following an excellent wet season in early 2020, the site has revegetated with pasture grass and seedlings are now well established. Monitoring of the site in May 2020, demonstrated successful rehabilitation following the first wet season. Further tube stock plantings and weed management is planned for the next 12 months.
Figure 2 Rehabilitated Avulsion Gully (April 2020)
Before and after construction and following revegetation images taken from around the primary project site, showing significant erosion issues in pre-construction images and fill, reshaping earthworks in post-construction images and commencement of effective revegetation by May 2020.
Before and after images taken from a drone of the large farm dam excavations, around the primary project site, with spillway formalisation works still being completed in the image in the middle. The final image is after construction following a good wet season.
Structurally complex fish habitats and coral reefs are in a state of steady decline, with much of the damage to high-quality habitat caused by human activity. Along the east coast of Australia, hard, vertical relief habitats such as oyster reefs, sub-tidal coral reefs and rocky outcrop reefs have been severely impacted by intensive land use practices, to the detriment of both fisheries resources and coral reef habitats.
In order to address the declining quality of hard, vertical fish habitat and to provide opportunities for coral reef growth, Fisheries Ecologists at Catchment Solutions set about designing artificial fish habitat structures, which also specifically incorporate features to promote and facilitate coral growth. Through consultation with recreational fishing experts, spearfisherman, divers, coral reef experts and fisheries biologists with experience in tropical Queensland waters, two key fish habitat designs were devised. Importantly, the fish habitat structures were designed specifically to;
The first design, termed the ‘Ledge and Cave’ habitat reef module, is constructed from pre-fabricated concrete components. This reef unit features a large central cave, with two smaller cave-like habitats attached along the outside walls providing additional surface area contact with the substrate to increase stability and reduce subsidence. Two large, round ‘table top’ plates are located above the central cave, providing overhanging shade and refuge over a large surface area. They also provide vertical habitat designed to manipulate tidal currents, creating eddies which attract bait fish and schooling pelagic fish species such as trevally and queenfish.
The second design termed the ‘Pyramid’ habitat reef module, is constructed from concrete cast into a large, steel mold of the reef module. The ‘Pyramid’ reef module features a central cave located within the bottom of the unit and an enclosed chamber in the top of the unit, only accessible through a series of small holes. It is anticipated that larger predatory species will utilise the lower cave, while juveniles and smaller species such as bream, mangrove jack, and baitfish will seek refuge within the enclosed chamber.
The habitat reef modules also incorporate design features critical to promoting coral colonisation, including high surface area, roughened external surfaces, small grooves throughout the roughened surfaces, and vertical and horizontal complexity in the form of underhangs and ledges. The calcium bicarbonate used in the concrete is also biologically suited to promoting and facilitating coral settlement and growth.
It is anticipated that the greatest benefit can be achieved by arranging four ‘Pyramid’ modules around a single ‘Ledge and Cave’ module as a ‘set’, and by placing a number of sets within close proximity to achieve maximum utilisation by fish, and coral recruitment. The habitat reef modules are suitable for a range of projects, including fish habitat improvement works at land-based recreational fishing access points, coral reef restoration activities, eco-tourism ventures for snorkeling and diving sites, and also through utilisation as fish-friendly mooring systems.
Catchment Solutions Senior Fisheries Ecologist, Matt Moore, who was recently interviewed by Greg Vinall of the Australian Lure Fishing Podcast, shared his knowledge on the importance of catchment connectivity and habitat availability to the sustainability of native fish populations.
The interview highlights a number of connectivity issues impacting the life-cycles of key commercial and recreational fisheries species throughout Queensland, and also strategies and remediation methods for addressing these impacts.
In February 2020, Catchment Solutions conducted fishway monitoring at a cone-ramp fishway which provides fish passage between upper-tidal estuarine habitats and a significant wetlands complex, at Koumala in the Rocky Dam catchment south of Mackay. The wetlands are surrounded by an extensive earthen bund wall, which features two fishways allowing fish to enter the wetlands. Importantly, the extensive wetlands provide an abundance of food and refuge habitat for fish and bird species and also provide habitat for saltwater crocodiles.
Figure 1. Image of the large wetlands which provide an abundance of habitat and refuge for native fish communities.
The cone-ramp fishway was constructed at the site in November 2015, along with a formal causeway and spillway allowing water to exit the wetlands during wet-season flows. Fish utilise the fishway through firstly being instinctively attracted to the freshwater flowing out of the wetlands. They then enter the fishway and use their burst speed to ascend through the ridges of the fishway, whilst also being able to rest in the large pools between the ridges as they make their way upstream. In central Queensland, it is generally the juvenile young-of-year recruits which migrate from upper estuarine habitats into freshwater wetlands, meaning that providing sufficient resting areas and suitable conditions throughout the fishway is critical to ensure small fish are able to ascend.
Figure 2. Left; cone-ramp fishway following dry-season construction in late 2015 and right; during fishway monitoring, with the fish trap visible at the top of the fishway.
The monitoring was strategically timed to coincide with wet-season flows during the warmer months, in the anticipation that these conditions would result in a high number of juvenile fish migrating up the fishway to enter the wetlands. Overall, an average of 1410 fish/day were captured migrating up the fishway, which was made up of ten species. This includes an average of 86 barramundi captured per day, which is among the highest numbers of barramundi ever recorded migrating up a fishway per day. Perhaps more importantly, the size range of these barramundi ranged from as small as 25mm through to 108mm, showing these fish are likely only weeks old, and utilising the fishway for life-cycle dependent migrations into the wetlands to utilise the abundance of food and refuge to grow rapidly. The results obtained show the value of providing aquatic connectivity at sites such as this, between fresh and saltwater habitats. This is not only of critical importance for general fish community health, but also for ensuring sustainable populations of species of socioeconomic value to commercial and recreational fisheries.
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.
Catchment Solutions have recently (August 2019) commenced on-ground works at the Collinsdale erosion remediation project site. The primary erosion remediation site is located at the Collinsdale Station, which is situated on the southern side of the Fitzroy River, in Garnant, approximately 30km from Rockhampton. The 450ha cattle property is situated within the Louisa Creek catchment and has been identified through Paddock to Reef modelling as contributing the 10th highest load of sediment to the Great Barrier Reef Marine Park from the Fitzroy basin area.
The Reef Trust IV Erosion Remediation project area includes the rehabilitation of large-scale gully erosion, using earthworks to reshape and fill the erosion scar, with the project, including;
Figure 1. Before (left) and after (right) images taken from a drone of the primary project site, showing significant gully erosion in pre-construction image and cut, fill and reshaping earthworks in post-construction image.
Following the completion of earthworks, which is anticipated to be late 2019, the site will have irrigation installed and be seeded, mulched and revegetated to reduce rainfall impacts on the rehabilitated gully area. The adjacent property located directly upstream, the Bindaree station, will also include an additional 4km of streambank and gully fencing.
Figure 2. Before (left) and after (right) images taken from around the primary project site, showing significant erosion issues in pre-construction images and fill and reshaping earthworks in post-construction images.
Figure 3. Before (left) and after (right) image taken from a drone of the large farm dam excavations, around the primary project site, with spillway formalisation works still being completed in the image on the right.
In early 2019, Catchment Solutions commenced a project aimed at addressing severe erosion in the Ogmore area of the Styx River catchment, funded through Reef Trust IV. Due to the sodic nature of the soil found within the Styx River Catchment, even with restricted grazing, active gully erosion is occurring at a significant rate. Paddock to Reef modelling has demonstrated that the Ogmore area contributes 26,880t of fine sediment to the Great Barrier Marine Park per year.
Figure 1. Severe erosion representative of the catchment land issues throughout the Ogmore region.
To minimise ongoing erosion, six demonstration trial plots are to be set up at the Oakdean Station, to assess and demonstrate various erosion remediation methods intended for future adoption of these methods throughout the broader Ogmore area. Erosion treatment methods to be trialled include combinations of gully reshaping, ripping (shallow <200mm), gypsum treatment (10t/ha), lime treatment and (2t/ha) and rhodes grass seed application (10kg/ha). Additionally, following any earthworks, mulching by Conservation Volunteers Australia will be undertaken to reduce rainfall impacts on the rehabilitated gully areas.
On completion of the project, the demonstration site will be used to hold remediation workshops to local landholders within the Ogmore area, providing for expansion of the treatments to other similar sites owned by neighbouring landholders within the catchment.
On-ground trial works of the project are anticipated to commence in October/ November 2019.
Figure 2. Additional gully erosion images from throughout Ogmore, where remediation trials will commence in late 2019.
In June 2019, fish passage from the Bakers Creek estuary into the Bakers Creek treatment train wetlands was rehabilitated through the installation of a rock-ramp fishway. The treatment train wetlands located south of Mackay were constructed in 2014, to serve as a series of sediment and nutrient retention basins, treating sugar cane runoff and improving water quality before entering the estuary. The spillway at the downstream limit of the treatment train wetlands unfortunately washed away and became a significant scour hole during extreme flow turbulence caused by tropical cyclone Debbie in 2017.
Figure 1. Left; the Bakers Creek treatment train wetlands, and right; large scour hole resulting from significant stream flows during tropical cyclone Debbie in the 2017 wet season.
Whilst primarily functioning as a water quality treatment train the extensive wetlands also provide abundant habitat for commercially and recreationally important fish species such as juvenile barramundi and a multitude of other native fish community species. Unfortunately, the extensive damage to the spillway following the cyclone resulted in effectively no fish passage for fish to enter the wetlands from the estuary. In order to provide aquatic connectivity between the wetland and estuarine habitats, Reef Catchments NRM group provided funding for Catchment Solutions to construct a rock-ramp fishway at the site.
Due to the significant height of the barrier (3.8m surface headloss) and the working space available at the site, the rock-ramp fishway was required to incorporate innovative design features to ensure sufficient flow dissipation and resting zones for fish. The fishway was constructed with 38 ridges and pools, with 100mm drops between each pool and 1m spacing between ridge rocks. Due to the relatively short spacing between ridge rocks, all ridge slots along the entire left side (facing upstream) were ‘blanked out’ with concrete, to create still water in every fishway pool along the entire left-hand side. This provides sufficient resting zones throughout the fish ladder for migrating juvenile fish ascending the structure to reach the nursery wetlands upstream. This fishway is now the highest rock-ramp fishway in Queensland, and possibly in Australia.
Monitoring of the structure during flow events of the 2019/2020 wet season are anticipated to yield extremely positive results in terms of utilisation by a range of species and size classes. The monitoring results obtained will be critical in validating the innovative design utilised at this barrier site. Monitoring results will likely lead to the uptake of this design at similar barriers throughout the state and across the country, where cost-effective rock-ramp fishways are often overlooked as a suitable fish passage rehabilitation option.
Figure 2. Top left; Scour hole at spillway before fishway construction, top right; commencement of lower ridge construction, mid left; construction near completion, showing upper ridges in place, mid right; completed fishway prior to concreting, lower left; concreting fishway in place, to precise ridge control heights, lower right; fishway during first flow event following construction and bottom; panoramic image of fishway during first flow following construction.
In June 2019, Catchment Solutions undertook a fish passage improvement project involving the repair of the Landings Road fishway which connects the upper estuarine reaches of Rocky Dam Creek (Rocky Dam catchment) to the Tedlands wetlands in Koumala, south of Mackay.
The rock-ramp fishway at the site was showing signs of significantly reduced functionality and was reaching the end of its anticipated design life. Recent advancements in fish passage construction developed through similar projects throughout the region were implemented in the repair of the fishway. Specifically, repairs to the existing fishway incorporated replacing some of the existing ridge and wall rock with larger rock, incorporating deeper resting pools and re-concreting the structure with fibre reinforced concrete for greater longevity, particularly with prolonged exposure to tropical conditions.
Figure 1. Left; Defective fishway (towards left of image) requiring repairs with the barrier height also visible showing 1.2m difference between upstream and downstream water levels. Right; one of 14 juvenile barramundi salvaged during repair works from the pool immediately beneath the fishway. These fish were congregating beneath the fishway, however due to the defects were unable to use the fishway to reach the upstream wetlands. Also trapped below the fishway were giant herring, sea mullet and bullrout.
The barrier at the site is comprised of a 1.2m surface headloss between Tedlands wetland (upstream) and the upper tidal limits of Rocky Dam Creek (downstream), resulting from the Landings Road causeway bisecting and separating the water bodies. Spring tides in the region reach the causeway, delivering a high number of juvenile diadromous fish species of high socioeconomic importance to the site. These species such as barramundi, giant herring, tarpon and sea mullet are required to reach the upstream nursery habitats of the extensive 150ha Tedlands wetland to complete their life-cycle. The rock-ramp provided this access upon its initial construction, however, in recent years has become compromised and defective, hence the requirement for repair works. Fish passage improvement works remediated a number of issues with the fishway through establishing increased depth within the fishway pools. Deeper pools provide essential resting areas for migrating fish by reducing turbulence and velocity. This ensures fish that may become fatigued during their upstream migration have an oppurtunity to rest and recover before utilsing their burst speed to successfully ascend through to the next ridge and eventually reach their upstream nursery wetland habitat.
These fish passage improvement works were co-funded by Mackay Regional Council and Reef Catchments NRM group, and are anticipated to provide significant increases to the biodiversity of this regionally significant wetland complex. Amongst an abundance of birdlife, crocodiles and numerous other fish species, the wetlands provide substantial habitat for young-of-year barramundi recruits. Extremely high numbers of juvenile barramundi migrate into these lowland wetlands during wet-season flows, where they grow rapidly due to the abundance of food and refuge habitat. These fish then migrate back to estuarine habitats as sub-adults to complete their life-cycle. Barramundi are a valuable fisheries resource throughout the region and broader central Queensland, with aquatic connectivity improvements to freshwater and wetland habitats a key strategy in increasing populations of the species for the benefit of commercial, recreational and indigenous fisheries. Due to the high numbers of juvenile barramundi migrating through the fishway and into the wetlands, local residents have nicknamed the fishway the ‘barra ladder’.
Figure 2. Top row; causeway prior to fishway repair works and wall rock replacing smaller original rock. Middle; fishway upon completion of repairs before (left) and after (right) new concrete being poured to seal the pools and solidify the structure. Bottom; fishway during first flows upon opening up causeway after concrete had set.
Scientists have engineered 150 tonnes of salvaged hardwood into ‘log jam’ structures to halt heavy erosion in Clyde Creek, Gladstone.
It is the first time the novel environmental solution has been used in the area.
And while log jams have been used in freshwater rivers previously, this could be the first successful attempt to install them in a tidal estuary in Queensland.
Five of the structures – each made up of 17 hardwood logs and weighing 25 to 30 tonnes – were lowered into Clyde Creek 10 months ago.
Aquatic ecologist Matt Moore (environmental consultancy Catchment Solutions), said the Clyde Creek bank had been retreating at an alarming rate of 0.25 metres each year.
The log jams combat erosion, and are designed to deflect water away from the river bank back into the centre of the water course.
In a triple-barrelled win, they also provide habitat for key recreational fish species like barramundi and mangrove jack; and give marine plants such as mangroves a chance to rehabilitate.
“The log jams give the creek bank a break. Previously, when fast water hit the bank in Clyde Creek, it was eroding badly, dropping sediment into the creek and out to sea. This solution benefits both the local waterway and ultimately the wider marine system. It means less pollutants washed out.”
Mr Moore said installing the log jams had been a stick-by-stick engineering feat in a tidal zone.
“We were racing against the tide to get the log jams in, with cranes and excavators on site.
“On a tidal flat, we can’t use machinery that is too heavy. The process is called stick building – we had a crane putting the logs into position one-by-one before the tide came back and washed us out!”
The log jams are five-storey engineered structures, about 3 metres high, with the logs arranged in a criss-cross pattern.
“We sourced salvaged native hardwood, that would otherwise have been wood-chipped or burnt,” Mr Moore said.
The natural ‘root ball’ ends of the logs were also kept attached as habitat structures for key fish species.
“Juvenile and adult fish can use the structures for protection from predators and currents and in turn this will be a real bonus for keen local fishers in the future!” Mr Moore said.
“The root balls provide ideal fish habitat where species like barramundi and mangrove jack can live and breed.
“It meant a lot more work was involved when extracting the salvaged trees, but we know fish love to take refuge in tree roots, and are attracted to them.
The log jams will also give marine plants such as mangroves a chance to recruit and re-establish. The local mangrove population will be monitored for improvements ahead.
Mr Moore said he was now keen to see the habitat structures replicated in other tidal estuaries and rivers across the state.
This project has been funded by the Queensland Government through the Department of Agriculture and Fisheries as part of offsets funding. The Engineered Log Jams were constructed by Catchment Solutions.
Catchment Solutions is leading the remediation of large-scale erosion at the Collinsdale property located about 30 kilometres north of Rockhampton.
The Collinsdale property is situated in the Garnant locality. This project involves the rehabilitation of large scale gully erosion using earthworks to reshape and fill the erosion scar, with about 20,000m3 of material to be moved and reshaped. Following reshaping, the site will be seeded and mulched to protect the top soil. The site will then be planted by Conservation Volunteers Australia with a mixture of native trees and bushes to enhance re-vegetation of the site.
To protect the site following remediation, fencing of the site and surrounding catchment along Louisa Creek will be undertaken. This fencing will be combined with the installation of off-stream watering points.
On behalf on Catchment Solutions, Neilly Group Engineering has undertaken flood modelling and a detailed design to undertake the remediation of the large-scale gully erosion. The attached video outlines the site planning and monitoring undertaken to obtain relevant government support and approval.
This project has been endorsed by the Reef Trust Technical Working Group (Gully and Stream Bank Erosion Control Program) and approved by the Department of Environment and Energy.
The project will be tendered in May 2019, with the project earthworks expected to begin by August 2019.
This project is funded by the Australia Government through the Reef Trust Program.
As it was the highest tide of the year, the team was able to observe the Styx River tidal bore, which reached the monitoring site upstream on Deep Creek, just off the Styx River.
Globally, estuarine habitats rank in the most modified of all marine ecosystems, driven primarily by coastal development. The urbanisation and infrastructure associated with population growth concentrate impacts on ecological communities of coastal regions, with anthropogenic advancement constantly recognised in the deterioration of estuarine process zones. Despite this, Queensland’s estuaries provide habitat to a range of species of significant commercial and recreational fisheries value, with many of these species having been documented to utilise highly urbanised marine fish habitats.
In Queensland, urban marine habitats are generally maintained by landholders, local councils and infrastructure management departments. Maintenance works can be routine (e.g. trimming marine plants on access tracks) or as required (e.g. repair of stormwater outlets) and involve varying levels of disturbance. While most maintenance works are required, there are potential risks to fisheries resources and marine plants, particularly when works procedures do not comply with legislative guidelines.
Figure 1. Example of an urban estuarine site showing signs of marine plant vegetation clearing and degradation, with inset of juvenile sea mullet (M. cephalus), barramundi (L. calcarifer) and mangrove jack (L. argentimaculatus) surveyed from the site.
For the purpose of guiding improvements to the management of urban marine fish habitats, Catchment Solutions conducted a 2-year project investigating and comparing the habitat utilisation by fish and crustacean species of urban, peri-urban and non-urban estuarine sites throughout central Queensland. Particular attention was paid to habitat usage of these areas by species of value to commercial and recreational fisheries. The primary objective was to show the critical habitat role that areas thought primarily of as urban ‘drains’ play in providing refuge for juveniles of important species. Furthermore, densities of marine plant vegetation such as mangroves were also surveyed to evaluate the role marine plants play in providing habitat for these species.
These objectives were achieved by carrying out a range of fish community sampling techniques across a number of different urbanised coastal fish habitat sites including tidal creek habitats (lower, mid and upper tidal sites) and supralittoral wetland habitats in the Rockhampton and Gladstone regions. Sampling techniques included a combination of seine netting, fyke netting, cast netting and the use of baited box traps to sample for fish and crustacean species.
In total, 78 species were recorded from 13 sites over five rounds of monitoring, demonstrating the exceptional diversity that can be found at such sites. This comprised 27 species recognised to be of socioeconomic importance to commercial and recreational fisheries. Analyses comparing overall species presence/absence between urban versus non-urban sites showed no significant difference between assemblages, which provides evidence that the highly urbanised sites surveyed are being utilised by identical aquatic assemblages to non-urban sites. Results also showed that for the species of 27 species of socioeconomic importance to commercial and recreational fisheries, the majority of the catch comprised post-larval and juvenile life stages. This highlights the role that coastal estuarine habitats (urban and non-urban) play in providing important nursery grounds to a high number of valuable inshore species, including barramundi, mangrove jack, sea mullet, mud crabs and banana prawns. Peaks in urban habitat utilisation by post-larval and juvenile individuals of species of socioeconomic importance were found between April and September, and numbers were at their lowest between November and December.
Figure 2. Species surveyed during the monitoring (top to bottom, left to right); 1) yellowfin bream (A. australis), 2) giant herring (E. hawaiensis), 3) barramundi (L. calcarifer), 4) Moses perch (L. russelli), 5) endeavour prawns (M. endeavouri), 6) northern whiting (S. sihama), 7) mud crab (S. serrata) and 8) giant queenfish (S. commersonnianus).
Correlations were identified between tidal connection, marine plant composition and the composition of fish/crustacean communities. There was insufficient data to determine whether any of these links were causal, however it is a reasonable assumption that both tidal connection and plant species composition (i.e. mangroves) play a role in the diversity and abundance of fish that utilise urban marine habitats. Review of marine plants surveyed across all sites identified a period of reduced reproductive activity (i.e. flowering and fruiting) between September and October.
Key conclusions from this research suggest that any maintenance works of urban marine habitats in central Queensland should be undertaken late in the dry season. This is to avoid peak periods of utilisation of these habitats by post-larvae and juvenile fish of socioeconomic importance and to avoid peak reproductive periods of marine plants. Where possible, a minimum 2m vegetation strip should be provided along all urban marine habitats to provide refuge habitat for aquatic communities utilising these areas.
It is anticipated that the outcomes of this work will guide future best management practices of urban fish habitats, such as frequency and timings of routine maintenance works adopted by local governments and land holders of the region. The study also provides a framework for similar research into the field of urban marine habitat utilisation and could be replicated to guide appropriate management of urban marine habitats in other regions of Queensland. Building on the dataset would also provide the opportunity to perform more detailed analysis on the causal links between tidal connection, marine plant composition and fish/crustacean diversity and abundance. Knowledge gained through this study could also be built on by investigating the contribution of urban marine habitats to the commercial and recreational catches.
Peacock bass are a large, predatory freshwater fish species native to South America. The attractive markings, large size and fighting qualities make the species a highly prized sportfish and extremely popular aquarium fish for hobbyist fish-keepers around the world. Despite this, the voracious nature and diet which consists primarily of juvenile fish, make the species a significant threat to fish communities when released outside of their natural range of the greater Amazon basin in South America.
In January 2018, reports circulated of a Mackay angler who had captured a peacock bass below Dumbleton weir in the Pioneer River. The capture represented the first substantiated reports of peacock bass in Australian waters and generated significant public interest and concern. The potential incursion of this species presented a significant threat to fisheries resources in Mackay, with this large predator capable of severely impacting the abundances of native fish communities.
Following the capture, Catchment Solutions were engaged to undertake extensive electrofishing surveys of the capture location and further throughout the Pioneer River to investigate the extent of the incursion of the species. Following the surveys, no peacock bass were detected in the catchment, suggesting numbers of the species were extremely low, if present within the system.
In January 2019, a further two separate captures of peacock bass were reported from the Gooseponds wetlands in the centre of Mackay’s urban area. These captures were also supported by photographic evidence and suggested that higher numbers of the species were prevalent throughout the Pioneer catchment than initially anticipated. Catchment Solutions were again tasked with investigating the captures, and additional electrofishing surveys were undertaken, however this time, focussing efforts throughout the artificial wetland lagoons of the Gooseponds which were not previously surveyed.
Boat-based electrofishing surveys were undertaken throughout the entire Gooseponds wetlands with each of the major lagoons, including all of the channels connecting the lagoons, being extensively electrofished. Unfortunately, two mature male peacock bass measuring 420mm and 395mm were collected during the surveys. These individuals were removed from the Gooseponds for genetic and gut content analysis in order to establish the origin of these fish, and also the feeding behaviours of these fish when unlawfully introduced into tropical Australian waters. It is likely that continued monitoring into the future will be required to ensure any remaining individuals are removed from the system to ensure an outbreak of the species does not arise.
Throughout the surveys, the capture of all additional species was also recorded. A diverse range of native species were captured in high abundances, showing the vital role the Gooseponds play in providing habitat to a range of important species. In total, 77 barramundi were caught throughout the Gooseponds, measuring from 220mm young-of-year recruits right through to large, 920mm mature adult fish. A rock-ramp fishway constructed at the downstream limit of the lowest lagoon provides fantastic access for juvenile barramundi to enter the Gooseponds from the Pioneer River estuary, where the juveniles can utilise the wetlands for refuge, feeding and growth. Many other diadromous, migratory species also utilise the rock-ramp fishway to access the Gooseponds including mangrove jack, sea mullet, giant herring, tarpon, banded scats and snakehead gudgeons.
Unfortunately, relatively high numbers of introduced tilapia were also caught during the monitoring, which have now become well-established in the Gooseponds since being first identified in the system only several years ago. This species is now one of the most prevalent species in the Gooseponds and highlights the speed with which pest fish can establish themselves when allowed to do so. This species is a declared noxious species in Australian waters and as with all pest fish, including peacock bass, if captured must not be released or distributed and must be immediately disposed of upon capture.
Above the introduced pest fish, tilapia, which were caught in the Gooseponds during the monitoring.
Background and Objectives
In July 2018, Catchment Solutions conducted a marine fish habitat rehabilitation project in Clyde Creek, Gladstone. The project aimed to achieve a range of outcomes by undertaking a holistic suite of system repair works through utilising large, engineered log-jam structures to stabilise a section of actively eroding streambank, while improving fish habitat for economically important species.
Specifically, the objectives of the project were to;
• Restore fish habitat function on a severely eroded estuarine creek bank by reconnecting fragmented marine plant communities,
• Prevent further erosion processes from degrading marine plant and fish habitats,
• Incorporate innovative structures to increase the availability of structurally complex fish habitat,
• Increase fisheries productivity by providing habitat for economically important fish species, such as mangrove jack and barramundi, and
• Reduce sediment export to downstream receiving environments i.e. Calliope River and Great Barrier Reef Marine Park.
Engineered log-jam structures were identified as the best remediation option to achieve the objectives at this site, with five structures, each containing 17 logs, constructed along the streambank. Log jams are permeable structures that extend into the stream for a short distance to deflect erosive stream flows away from the streambank into the main channel, thus preventing further erosion. This promotes the deposition of sediment on the downstream side of the structure, thus providing adequate substrate for growth of marine plants. It is the re-colonisation of marine plants at the site that will repair the streambank into perpetuity, and it is the role of the log jams to provide the correct hydraulic conditions (reduced bank velocity) and deposition areas for marine plants to colonise. Importantly, the log-jam structures have the advantage of providing critical, structurally-complex instream habitat for a range of socioeconomically important fish species.
Figure 1. Site images before remediation works, showing extent of erosion and degradation of the streambank and the lack of instream fish habitat and marine plant colonisation.
Log Jam Construction
A slew crane was utilised to lower each log, one at a time, into voids created in the streambank (Figure 2). Once all 17 logs of the structure had been positioned in place, 12 mm fibre core wire rope was used to secure all logs of the structure together. A lever block was utilised to provide maximum tension on the fibre core wire rope, ensuring no slip or movement of logs within the structures. 7 m pin logs were then driven into the substrate outside of the structures to provide further stabilisation (Figure 3 and Figure 4).
Figure 2. Slew crane lowering logs into position.
Figure 3. Structure near completion, showing first fibre core rope secured around the structure.
Figure 4. Structure with fibre core wire rope secured and 7 m pin logs driven into substrate for further stabilisation.
The final step in securing the structures in place was to back fill the voids structures were built within using rock. An excavator was used to fill the voids and compact the rock around the structures, to firmly lock the structure into position within the streambank (Figure 5 and Figure 6).
Figure 5. Side profile of completed structure with rock fill and armouring in place.
Figure 6. Image of completed structure, with rock fill and armouring in place.
Following completed construction of all five structures, when all construction machinery had vacated the site, a single excavator was used to batter the top section of slumping streambank back to a 1V: 3H gradient (Figure 7). This will minimise future erosion and provide suitable conditions for the re-colonisation of mangroves and other marine plants. Once established, the marine plant communities will further consolidate the reformed streambank and provide additional fish habitat into the future.
Figure 7. All five log-jam structures and the battering of the top metre of streambank to reduce future slumping and facilitate marine plant colonisation.
Figure 8. Structure 4 and structure 5 at downstream extent of site (left) and close up of rootballs of structure 4 (right).
Project Outcomes
The engineered log-jam structures will rehabilitate the actively eroding streambank by dissipating and deflecting stream flows away from the impacted streambank and back into the centre of the waterway. The structures also encourage the deposition of sediment transported from the upper catchment. This deposition will occur in areas of low velocity, on the downstream side of the structures. Future marine plant communities established due to the remediation works will eventually reconnect with remnant communities upstream and downstream of the works, stabilising and protecting the streambank from continued erosion. Additionally, the large rootballs present within the structures will provide critical habitat for a range of socioeconomically important fish species (Figure 9).
Figure 9. Before and after photos of remediation works (top; facing downstream and bottom; facing upstream)
Benefits to Fisheries Resources
The primary benefit of the project to fisheries resources, is through the provision of critical, structurally complex habitat, specifically, during low tide periods. Due to the previous years of active erosion at the site, available habitat is virtually non-existent at low tide. The structures now provide a number of locations where important commercial, recreational and indigenous fishery species such as barramundi, mangrove jack, threadfin salmon and bream, can seek refuge (Figure 10). These structures will also provide crucial refugia habitat on high tides for juvenile fish and baitfish species such as mullet, herring and glassfish for predator avoidance.
Figure 10. Image of structurally complex rootballs (left), three-dimensional habitat within the log-jams (right).
Future Monitoring
Future monitoring will continue to assist in determining project success and help convey results to stakeholders. Monitoring activities will include monitoring marine plant establishment to describe species composition, community structure and size class densities, sediment erosion/deposition on the streambank and fish community monitoring will also occur via underwater video analysis utilising baited and unbaited cameras (Figure 11).
Figure 11. Baited remote underwater video (BRUV) system utilised for monitoring at the site