Category Archives: Pest animal issues & solutions

Assessing the effectiveness of Integrated Pest Management in Queensland

Key words: Integrated Pest Management, pest fish control, Native Fish Strategy

Threats and Impacts: Carp (Cyprinus carpio) are believed to impact on native fish communities by increasing turbidity, up-rooting delicate shallow-rooted vegetation, competing with native fishes and other aquatic fauna for food and space, and indirectly promoting the development of toxic algal blooms.

All of the currently available methods for Carp control have limitations. Integrated Pest Management (IPM) involves the application of a range of technologies applied simultaneously, and focussing on achieving broader objectives (e.g. improved habitat) rather than simply reducing pest numbers.

Broad aim and specific objectives: The objectives of this project were to apply a range of Carp control techniques, as an integrated package, to:

  • intensively reduce Carp at a particular location, and measure the response;
  • achieve a significant reduction in damage caused by Carp using existing techniques; and,
  • demonstrate to the community the commitment to on-ground control.

The study was conducted at four lagoon sites, two in the Condamine River catchment, and two in the Macintyre river catchment.

Methods: One lagoon in each catchment was selected as an experimental site for intensive carp removal, and the other was used as a reference site which received no carp treatment.

Each site was sampled on eight occasions for the following response variables: water quality (temperature, pH, conductivity, turbidity, dissolved oxygen, light penetration, available forms of nitrogen and phosphorus); phytoplankton biovolume and diversity; zooplankton biomass and diversity; benthic macroinvertebrate abundance and diversity; native fish abundance, biomass and diversity; carp abundance, biomass and size distribution; and abundance of piscivorous birds and turtles.

One sampling event was conducted before the carp reduction treatment and a further seven samples were performed after Carp reduction. Carp removal employed a variety of methods based on boat electrofishing, gill nets, fyke nets, angling, commercial-scale netting and traps, and screens to prevent re-entry of Carp.

Figure 1: electrofishing during carp removal at rainbow lagoon. (Photo courtesy Peter Gehrke)

Figure 1: electrofishing during carp removal at rainbow lagoon. (Photo courtesy Peter Gehrke)

Figure 2: Researcher Sarah St Pierre live picking macroinvertebrates (Photo courtesy of Nissa Murphy)

Figure 2: Researcher Sarah St Pierre live picking macroinvertebrates (Photo courtesy of Nissa Murphy)

Findings: In Rainbow Lagoon (one of the experimental sites), Carp removal achieved an estimated 51% reduction in abundance and 43% biomass reduction, compared with 41% abundance and 33% biomass reductions in Warra Lagoon (the other experimental site). Reduction of Carp biomass by approximately 30 kg per ha allowed a threefold increase of more than 90 kg per ha in native fish that are eaten by larger fish species and fish-eating birds.

The size and weight of Carp removed differed markedly between Warra Lagoon and Rainbow Lagoon. Rainbow Lagoon had large numbers of small Carp, while Warra Lagoon had relatively large numbers of big Carp, with relatively few small individuals. The differences in Carp populations between lagoons are likely to result in different ecosystem responses over time.

Boat electrofishing was the most effective method of Carp removal used; fyke nets were the second most effective method, while the number of Carp removed by angling was far lower than other methods.

A succession of ‘transient’ responses to Carp reduction was observed in treatment lagoons. Whilst the exact nature of succession differed between lagoons, the generalised pattern following Carp reduction was evidenced as (i) an increase in biomass of large zooplankton; (ii) an increase in abundance of benthic macroinvertebrates; and (iii) increased biomass of gudgeons (Hypseleotris spp.) and Bony Herring (Nematalosa erebi).

These results suggest that of the full set of potential ecosystem responses to Carp reduction, only a subset may be demonstrated in individual locations because of the influence of local drivers and constraints. Due to a range of factors, the environmental responses of several variables, including water quality, macrophytes, zooplankton and macroinvertebrates, could not be linked to Carp control.

Lessons learned and future directions:Modest reductions in Carp biomass can provide significant benefits for native fish and, if continued, may be expected to translate into longer-term increases in native fish populations.

  • Carp in turbid wetlands interact strongly with native fish through pelagic food web pathways involving zooplankton, as well as benthic macroinvertebrate pathways.
  • Carp reduction has the potential to contribute significantly to restoring populations of native fish by increasing food availability.
  • Environmental outcomes of Carp reduction include direct conservation benefits to native fish, potential increases in popular recreational species and improved aquatic ecosystem health.
  • Piscivorous fish (e.g. Murray cod, Maccullochella peelii) are likely to have increased prey availability as a result of Carp reduction.
  • Improving native fish populations in key wetlands by reducing Carp biomass may strengthen the value of permanent lagoons as drought refuges for native fish.

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contact: Sarah St Pierre, SMEC. Tel: + 61 (07) 3029 6600.

Link: http://www.finterest.com.au/wp-content/uploads/2013/07/MD923%20Integrated%20pest%20management%20QLD.pdf

The potential for Mozambique Tilapia to invade the Murray–Darling Basin and the likely impacts: a review of existing information

Key words: Tilapia, pest fish, invasion risk, Native Fish Strategy

Threats and Impacts: Mozambique Tilapia (Oreochromis mossambicus) is a major pest fish species in Australia (Fig 1). A successful invader, it has managed to dominate natural waterways into which it has been introduced. It is not currently found in the Murray–Darling Basin; however, it has established thriving populations in catchments neighbouring the Basin. In some places, it is only a short distance from the northern headwaters. There is a high risk that this species will be introduced to the Basin.

Project aims and methods: Despite the high risk of introduction, prior to this project minimal work had been done to estimate the potential range Tilapia might occupy in the Basin, or to predict its possible impacts on natural, economic or social assets. This project set out to review available literature and assess likely impacts in an attempt to provide some information about these potential threats.

In order to estimate the potential range of Tilapia in the Murray–Darling Basin, this project set out to to:

  • predict the range in the Basin where Tilapia may survive through colder winter temperatures;
  • determine the length of the feasible breeding season (including the number of broods possible in that time) in different ranges; and,
  • determine the portion of the year in which Tilapia may feed and is therefore likely to have impacts on ecological processes through the food web.

This included:

  • estimating the lower temperature tolerance for Tilapia based on literature and survival rates of populations already infesting locations in Queensland;
  • identifying the minimum winter temperatures recorded at different locations throughout the Basin; and,
  • using the distribution of native fish with similar temperature tolerances to Tilapia as a surrogate.
Figure 1. Female Mozambique Tilapia carrying juveniles in her mouth (Photo courtesy of QLD DAFF)

Figure 1. Female Mozambique Tilapia carrying juveniles in her mouth (Photo courtesy of QLD DAFF)

Figure 2. male Mozambique Tilapia (Photo courtesy of QLD DAFF)

Figure 2. male Mozambique Tilapia (Photo courtesy of QLD DAFF)

Figure 3. Stunted Tilapia (male top, female bottom) mature at only a few centimetres in length, (Photo courtesy of QLD DAFF)

Figure 3. Stunted Tilapia (male top, female bottom) mature at only a few centimetres in length, (Photo courtesy of QLD DAFF)

Findings: Tilapia has a wide and varied diet and can occupy a diverse range of habitats, however, the one factor that appears to affect Tilapia is its vulnerability to cold temperatures. Based upon minimum temperature tolerated by Tilapia and the minimum water temperature data available, Tilapia have the potential to infest the northern Basin in Queensland and parts of New South Wales, through the western inland catchments of NSW and down to the Lower Lakes and lower Murray in South Australia. This equates to a distribution occupying approximately half of the MDB.

Tilapia is capable of sustaining reproducing populations under the conditions found in much of the MDB, as breeding and feeding can occur for significant portions of the year. In the northern parts of the Basin, and many southern parts, median water temperatures could see a breeding season of at least 3–6 months in duration with around 4–6 broods for each female in each breeding season.

Tilapia impacts have been recorded in a number of locations both in Australia and overseas. The key impacts recorded include major declines in commercial and traditional fisheries, fish extinctions, destruction of beds of aquatic plants) and declines in water quality. Some of the predicted direct impacts of Tilapia on the Murray–Darling Basin include:

  • direct predation by Tilapia;
  • competition for resources (food, habitat);
  • destruction of macrophytes and other aquatic plants used as breeding or nursery habitat by native species;
  • habitat disturbance;
  • transmission of diseases and parasites;
  • competitive exclusion of native fish from favourable habitat by tilapia’s aggressive behaviour;
  • increase of blue-green algal blooms (through resuspension of nutrients);
  • winter die-offs of tilapia (polluting waterways); and,
  • undermining river banks due to destruction of river plants and nesting behaviour.

Review of recent studies indicate that Tilapia consume juvenile native fish, including members of genera that occur in the Murray–Darling Basin, such as Rainbowfishes (Melanotaeniidae), Carp Gudgeons (Hypseleotris spp.), Hardyheads (Atherinidae), Bony Herring (Nematalosa erebi) and Glassfish (Ambassidae). It is possible that the potential preying of tilapia on native fish has been underestimated. 

Lessons learned and future directions: This project highlighted that invasion of the MDB by Tilapia could be disastrous for many (up to 18) native fish species of the MDB. Areas and species most at risk from Tilapia and the likely impacts if invasion occurred were identified. The study recommends a ‘prevention is better than cure’ approach with respect to Tilapia invasion and highlights education and awareness as a key factor. This review should be most pertinent in areas close to current distribution of wild tilapia populations (i.e. north-eastern MDB). 

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Dr Michael Hutchison, Queensland Department of Agriculture Fisheries and Forestry. Tel: + 61 7 3400 2037, Email: Michael.Hutchison@daff.qld.gov.au

Link http://www.mdba.gov.au/sites/default/files/pubs/Tilapia-report.pdf

Behavioural aggression in Gambusia holbrooki is conditional upon temperature and relative abundance.

Key words: Eastern Gambusia, aggression, pest fish, Native Fish Strategy.

Threats and Impacts: Introduced to Australia in 1925 as a potential mosquito control agent, the fish Gambusia (Gambusia holbrooki) (Figs 1 and 2) is now present in almost every major Australian drainage, including the Murray-Darling Basin. Gambusia are extremely aggressive, harassing, predating and attacking native fish; and are thought to also pose a significant threat to many amphibians and invertebrates.

Broad aim, specific objectives and methods: This project explored in aquaria how aggressiveness of Gambusia changed according to the relative abundance of two native fish species (western carp gudgeon Hypseleotris spp. and juvenile Golden Perch Macquaria ambigua). Five treatments were run involving  combination of Gambusia to native fish ratios and temperatures. The project was designed to improve understanding of how Gambusia might behave when it colonises new areas and how behavioural responses might be affected by efforts to control their numbers.

Figure 1: Female Gambusia. Note that all fish are in gravid condition. (Photo courtesy of Tarmo Raadik.)

Figure 1: Female Gambusia. Note that all fish are in gravid condition. (Photo courtesy of Tarmo Raadik.)

Figure 2: Mature female Eastern Gambusia (photo courtesy of Tarmo Raadik)

Figure 2: Mature female Eastern Gambusia (photo courtesy of Tarmo Raadik)

Findings: The study found that Gambusia were highly aggressive towards both species of native fish and that aggressiveness increased when Gambusia were outnumbered by native fish. The study also found that the type of aggressive behaviour by Gambusia (e.g. biting or chasing) was specific to the native species it was interacting with. Gambusia were shown to dominate the available habitat within the tank very shortly after introduction. The high aggression and dominance behaviour exhibited by Gambusia when outnumbered assist this species when invading new habitats and may also have implications for eradication efforts aimed at this invasive species.

Lessons learned and future directions: The increased aggression by Gambusia when outnumbered potentially means that control efforts that reduce the abundance of Gambusia but don’t fully eradicate them may not be beneficial to native fish in some cases. The research suggested that aggressive interactions from Gambusia may not decrease as a result of eradication efforts.

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Dr Andy Moore, Department of Agriculture Fisheries and Forestry. Tel: + 61 2 6272 3090, Email: anthony.moore@daff.gov.au.

Link: http://www.finterest.com.au/wp-content/uploads/2013/07/MD1224%20Gambusia%20Aggression.pdf

Preliminary investigation of an “Achilles Heel” for control of Redfin Perch in New South Wales

Key words: Perca fluviatilis, Redfin Perch, invasive species, physical removal, control strategy, Native Fish Strategy.

Threats and Impacts: Redfin Perch (Perca fluviatilis) is an alien fish species that has been established in Australia for more than 150 years. Although a popular recreational angling target in some regions, it has a range of deleterious impacts on native fish, through predation and competition for resources, and as a vector for a virus (epizootic haematopoietic necrosis virus). Despite the threat posed by this species, there are major deficiencies in current knowledge and policies in regards to controlling existing populations and responding to new infestations. In New Zealand and Australia the control of Redfin Perch has been found to be most effective in small lakes and ponds using physical removal techniques such as nets and traps, as well as mid-water trawling and electrofishing at night.

Project objectives and methods: The objectives of this project were to:

  1. undertake a detailed literature review of species biology to identify weaknesses that could be exploited in control programmes;
  2. conduct field trials of potential control techniques;
  3. complete an investigation of behaviour and movement using acoustic technologies; and,
  4. provide recommendations for a future control programme, including scoping of sterile feral technology.

This study included a detailed literature review of Redfin Perch biology to identify any potential weaknesses that could be exploited in control programs. Field trials were then performed in an impoundment (Suma Park Reservoir) on the central tablelands of New South Wales, known to contain an abundant population of Redfin Perch, and a riverine site in the Gwydir catchment. The trials were designed to investigate the effectiveness of physical removal of Redfin Perch using a combination of electrofishing, panel (gill) netting (with and without herding), fyke nets and clover-leaf traps with several attractants (laser lights, glow sticks, magnets and berley). The study also used underwater acoustic cameras (DIDSON) to examine Redfin Perch behaviour in response to each of the attractants. Separate trials were undertaken in winter and summer. Additional field trials were undertaken in a riverine site in the Gwydir catchment during summer.

Given the limited understanding of the species movement patterns and the importance of this information to targeting control techniques, an acoustic tagging study was undertaken in Suma Park Reservoir.

Figure 1 A cloverleaf trap such as those used during field trials (Photo courtesy of Dean Gilligan)

Figure 1 A cloverleaf trap such as those used during field trials (Photo courtesy of Dean Gilligan)

Figure 2 The focus species for this study, Redfin Perch (Photo courtesy of Dean Gilligan)

Figure 2 The focus species for this study, Redfin Perch (Photo courtesy of Dean Gilligan)

Findings: The review of Redfin Perch biology highlighted several key aspects that could be exploited in future control programmes:

  •  timing of reproduction – target removal prior to or during spawning events;
  • inducible sterility – sterile feral technology;
  • spawning behaviour – removal/reduce availability of spawning substrate;
  • self regulation of populations – bio-manipulation or sterile technology; and,
  • schooling behaviour – target control efforts.

In the removal trials, catch rates in fyke nets and cloverleaf traps were relatively low across all three trials (winter and summer in reservoir and summer in river) with standard panel nets and electrofishing being the most effective methods. The clover-leaf traps were not effective at catching Redfin Perch, either with or without attractants within the traps. Catch rates in cloverleaf traps and fyke nets were too low to draw any conclusions relating to improvements in catch efficiency resulting from the use of the attractants trialled. However, assessment of the response of Redfin to the various attractants using DIDSON imagery revealed that glow sticks and lasers do have the potential to be used as attractants, particularly at night.

The acoustic telemetry study indicated that most fish occupied the downstream end of the dam, with only up to two individuals spending extensive periods of time within the upstream reaches of the impoundment. Overall, fish spent 90% of the time within the top 10 m of the water column, possibly due to lower dissolved oxygen concentrations below this depth.

Lessons learned and future directions: Overall this project has resulted in the compilation of valuable information on Redfin Perch that can contribute to its future management. In particular:

  • passive fishing techniques/traps that rely on luring/attracting fish into a certain area (e.g. clover-leaf traps) are not very effective;
  • they appear to be much more susceptible to being caught in nets that target/intercept fish while moving (fyke and panel nets);
  • electrofishing is effective in the short-term and on a small scale, but may not be cost effective/practical in the long term as abundance of the target population declines;
  • glow sticks and laser lights were found to be effective attractants at night, but optimal deployment methods need to be established that minimise trap-avoidance of those fish attracted;
  • juveniles form large schools, whereas adults were more solitary; and,
  • movement data indicates the top 10 m of the water column and areas around the deeper downstream reaches of impoundments are occupied most frequently and may be appropriate areas to target removal efforts. 

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Dr Dean Gilligan, New South Wales Department of Primary Industries. Tel: + 61 2 4478 9111, Email: dean.gilligan@industry.nsw.gov.au

Design and installation of a novel wetland Carp harvesting set up at Lake Bonney, South Australia

Key words: Carp, pest fish control, Lake Bonney, Native Fish Strategy

During 2009–2010, Lake Bonney (near the township of Barmera in SA) received 26 gigalitres of environmental water from the Murray River. It was anticipated that Carp (Cyprinus carpio) would accumulate in large numbers at the lake inlet as water was delivered (Fig1), providing a unique opportunity to trial a wetland Carp separation cage (WCSC) for controlling the estimated 50–100 tonnes of this species in the lake, as well as a number of designs for screening fish. Although numerous types of screens have been used to restrict the movement of fish either into or out of wetlands, most do not achieve the best environmental outcome in terms of allowing the free passage of native fish and other fauna while restricting the movement of Carp and other unwanted species.

Project aim and methods: Fishing/tagging activities and monitoring in the lake proper were undertaken in association with delivery of an environmental watering to Lake Bonney, and installation of a prototype wetland carp separation cage, to evaluate:

  • The population of Carp and other large-bodied native fish (>250mm total length at maturity) in Lake Bonney including Murray Cod (Macculochella peelii), Golden Perch (Macquaria ambigua), Silver Perch (Bidyanus bidyanus), Freshwater Catfish (Tandanus tandanus) and Bony Herring (Nematalosa erebi).
  • The response of Carp and native fish during the provision of environmental water, and therefore the need to accommodate the passage of large-bodied native fishes during future water allocations; and
  • The species diversity, abundance and size structures of captured fish (Carp and large-bodied fishes)

Two new carp exclusion screens (jail bars with 31mm apertures between the bars and square grid-mesh with 44 x 44 mm internal dimensions) (Fig 2) were trialled in the culverts to evaluate:

  • their effect on flow velocity; and,
  • whether an angle-mount and the high flow-velocities in the culvert would combine to clear the screens by pushing debris towards the water’s surface (and potentially over the top of the screen).

Findings: Scientific sampling and commercial fishing activities within the lake and inflow point, combined with fish tagging, allowed estimation of the resident population of several large-bodied fish species (native and alien), and their response to inflow. The size of the resident adult Carp population was estimated via a Peterson mark-recapture tagging experiment at 44,606 individuals. A similarly large but unquantified biomass of Bony Herring was also detected. Otherwise, only three large Freshwater Catfish and two Golden Perch were recorded, suggesting the lake’s large-bodied native fish population is very low (with the exception of Bony Herring).

Carp were observed to aggregate in large numbers around the inflow point, and spawning activity was observed within 24 hrs. Their efforts to exit the lake via the culverts was blocked by the carp screen. In contrast, relatively few large Bony Herring and no other large-bodied native fish were captured near the inflow point, however thousands of juvenile Bony Herring were observed in January 2010 when Carp were absent.

Significant refinements to strengthen Carp screens; enable them to pivot; and, prevent public access were required to enable carp screens to operate without fouling with debris, and to prevent vandalism. When set to an angle of ~33° fouling and flow constriction was significantly reduced. Most entrained fish and turtles were also able to pass over the top of this design.

Figure 1 Carp in Lake Bonney (Photo courtesy of Leigh Thwaites)

Figure 1 Carp in Lake Bonney (Photo courtesy of Leigh Thwaites)

Figure 2 Carp cage installed at Lake Bonney (Photo courtesy of Leigh Thwaites)

Figure 2 Carp cage installed at Lake Bonney (Photo courtesy of Leigh Thwaites)

Lessons learned and future directions: Although the cage operated according to its intended design and function during the 2010 trial, some operational issues were observed, necessitating refinements that have resulted in a pragmatic, adaptable and safe device.

Fixed screens such as grid mesh and the ‘jail bar’ design should not be used at wetlands like Lake Bonney that have high flows and easy public access, because:

  • impeding Carp movement is inefficient and often obstructs native species
  • regular maintenance is required
  • they tend to deteriorate over time, and can be easily vandalised
  • they can compress Carp into wetlands (ie juvenile Carp pass through a screen and grow to a point where they cannot move out though the screen).

While commercial fishing can be a valuable tool for controlling Carp, it is of limited use as a ‘stand alone’ technique as netting a proportion of adult fish does not stop Carp from spawning.

The level of by-catch (356 Bony Herring, as well as a few Golden Perch, Goldfish (Carrassius auratus) and Birds) signals the need to survey the resident native fauna on a site-by-site basis prior to installing any Carp management infrastructure. Also, the motivation of Carp to migrate out of the lake decreased over time, suggesting that harvesting should occur in the early stages of the lake being filled.

 

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Dr Leigh Thwaites, South Australian Research and Development Institute. Tel: + 61 8 8207 5495, Email: leigh.thwaites@sa.gov.au.

Link: http://www.sardi.sa.gov.au/__data/assets/pdf_file/0019/153226/Proof_of_concept_of_a_novel_wetland_carp_separation_cage_at_Lake_Bonney,_South_Australia.pdf

Assessing the recovery of fish communities following removal of the introduced Eastern Gambusia

Key words:  Gambusia holbrooki, pest species control, native fish recovery, Native Fish Strategy.

Threats and Impacts: Alien fish species have been recognised as one of eight major threats to native fish in the Murray–Darling Basin (MDB), and the control of these species is one of the key drivers of the Native Fish Strategy. There is growing evidence of detrimental impacts of Eastern Gambusia (Gambusia holbrooki) on native fish fauna globally, and this species has been identified as potentially one of the key alien species contributing to the decline of a number of native fish within the MDB, where it is widespread (Figs 1 and 2). The ecological impacts of the Eastern Gambusia in the MDB remain uncertain and this project addressed these research needs by integrating surveys and experimental work in natural billabong systems throughout the MDB.

Broad aim and specific objectives: The specific objectives of the project were to:

1. Review current knowledge of the impacts of Eastern Gambusia on native fishes of the MDB.

2. Provide information on the response of native fish communities following the reduction of Eastern Gambusia populations.

3. Provide a framework to evaluate the feasibility and effectiveness of such control actions and form a template for evaluating control options for other alien fishes across the MDB.

Figure 1: Mature female Eastern Gambusia (photo courtesy of Tarmo Raadik)

Figure 1: Mature female Eastern Gambusia (photo courtesy of Tarmo Raadik)

Figure 2: High density of Eastern Gambusia in a shallow backwater environment (Photo courtesy of Tarmo Raadik)

Figure 2: High density of Eastern Gambusia in a shallow backwater environment (Photo courtesy of Tarmo Raadik)

 

Methods: The project was divided into four phases. The first phase involved a review of current knowledge of the impacts of Eastern Gambusia on native fishes of the MDB. The second phase involved a broad-scale, cross-sectional study of wetland fish communities to develop hypotheses about the effect of Eastern Gambusia on native fish communities in these enclosed systems. The third phase was a field trial of Eastern Gambusia control in small isolated billabongs, to test the hypotheses through density manipulation experiments and to provide information on control options and Eastern Gambusia population dynamics. The fourth phase identified strategies to maximise the level of improvement to the native fish community through Eastern Gambusia control given a fixed budget (benefit maximisation), and to minimise the cost of achieving a defined significant improvement in the native fish community (cost minimisation). Finally, the project provided a template for evaluating control options for other alien fishes across the MDB.

Findings: The review of literature exploring impacts of Eastern Gambusia on native fishes of the MDB identified that 16 of 37 native species have major habitat or diet (or both) overlaps with Eastern Gambusia. The most significant overlaps were with small-bodied species e.g. Glassfish (Ambassidae), Pygmy-perches (Nannopercidae), Rainbowfishes (Melanotaeniidae), Hardyheads (Atherinidae), Gudgeons (Eleotridae) and Smelt (Retropinnidae). The review therefore concluded that Eastern Gambusia is likely to have contributed to the decline (in distribution and/or abundance) of the Olive Perchlet (Ambassis agassizii), Southern Pygmy-perch (Nannoperca australis), Murray-Darling Rainbowfish (Melanotaenia fluviatilis) and Purple-spotted Gudgeon (Mogurnda adspersa).

An assessment of wetland communities throughout the mid-Murray region of the MDB found that Carp Gudgeon (Hypseleotris spp.) and Eastern Gambusia were the dominant species in both abundance and distribution. The results of the survey suggest that Eastern Gambusia do not have a negative influence on abundances of the more common native species (e.g. Carp Gudgeon and Flat-headed Gudgeon (Philypnodon grandiceps) most likely due to the generalist nature of such species enabling co-existence. Gambusia were found to impact on the abundance of juveniles of several native species, and on their general health by ‘fin nipping’

Several small isolated billabongs had Eastern Gambusia removed to observe how native fish would respond. During this trial, astonishingly, a few individual Eastern Gambusia were able to re-establish populations of thousands within three or four months. Most importantly, the results of the removal trial indicate that reductions of Eastern Gambusia abundances will result in some improvements to small-bodied native fish populations, and these effects may be enhanced within billabongs without complex habitat (making Gambusia easier to catch and remove), and containing native species with quite specific diets.

In examining the cost-effectiveness and logistics of Eastern Gambusia removal, this study presents a strategy to determine the feasibility of removal for different scenarios and concluded that the highest benefits per dollar invested were for habitats with low frequency of connection to other Eastern Gambusia populations, low structural complexity and of high ecological value.

Lessons learned and future directions: This project provides fundamental ecological information necessary for management of Eastern Gambusia. This project provides managers with a decision making tool to assess the cost benefit of Eastern Gambusia removal for a range of habitat scenarios. This will result in better targeted action of controlling this pest species and maximise benefits to native fish populations. This project will raise awareness of the impacts of Eastern Gambusia on native fish and what benefits may be obtained for native fish following Eastern Gambusia removal.

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Zeb Tonkin, South Australian Research and Development Institute. Tel: + 61 3 9450 8600, Email: zeb.tonkin@depi.vic.gov.au.

Evaluation of carp exclusion screens at wetland inlets

Key words: pest fish control, European Carp, exclusion screen, Native Fish Strategy

Threats and Impacts: Wetlands are sites of high primary and secondary production and contain diverse flora and fauna. Indeed, many riverine species are wholly or partially dependent on wetlands for food, shelter or habitat during some part of their life cycle. Carp (Cyprinus carpio) dominate the alien fish fauna of the Murray–Darling Basin, and are believed to impact on native fish communities by increasing turbidity, disturbing and redistributing benthic seeds and invertebrates, up-rooting delicate shallow-rooted vegetation, competing with native fishes and other aquatic fauna for food and space, and indirectly promoting the development of toxic algal blooms (Fig 1).

In the Murray-Darling Basin, up to 98% of Carp are produced in wetlands connected to the main rivers. Carp Exclusion Screens (CES), which are mesh barriers that are installed at inlets to wetlands to exclude large fish from enterin (Figs 2-3), provide a management tool that has been applied to protect ecologically important areas from the impacts of Carp. However, little work has been undertaken to validate the effectiveness of CES in managing Carp, and concerns about possible detrimental effects of CES on native aquatic fauna have been raised.  

Broad aim and specific objectives: The project had three broad aims:

  1. evaluate the effectiveness of CES at wetland inlets;
  2. assess possible impacts of existing screen configurations on native fish communities that would normally access wetlands; and,
  3. design (if possible) an optimised CES to allow small and medium sized native fish to pass in and out of wetlands whilst denying access to mature carp.

Methods: The aims of this project were achieved by undertaking six key research activities:

  1. a desktop literature review and a field reconnaissance to evaluate the existing diversity in the design and management of CES within the Murray–Darling Basin;
  2. analysis of available data from recent comprehensive wetlands surveys (the 2004–2007 South Australian River Murray Wetlands Baseline Surveys) to evaluate differences in the relative abundances of carp and native fishes in wetlands with and without CES;
  3. identification of the species composition and sizes of fishes and other aquatic fauna that make lateral migrations through wetland inlets and which might, therefore, be affected by the use of CES;
  4. modelling to establish the size range of large-bodied fish that could pass through different screen mesh dimensions;
  5. calculation of ‘optimised’ mesh designs that would prevent the passage of mature, breeding-size carp (>250 mm TL) whilst allowing the passage of a majority of small and medium sized native fishes that use wetlands; and,
  6. laboratory and field trials of the most common existing screen mesh designs versus the optimised designs.
Figure 1: Carp accumulating downstream of a Carp exclusion screen at Sweeneys wetland. (Photo courtesy SARDI)

Figure 1: Carp accumulating downstream of a Carp exclusion screen at Sweeneys wetland. (Photo courtesy SARDI)

Figure 2: Carp Screens installed on a channel at Riverglades SA.  (Photo courtesy Leigh Thwaites)

Figure 2: Carp Screens installed on a channel at Riverglades SA. (Photo courtesy Leigh Thwaites)

Figure 3: Pivoting carp screen adjustment at Ramco SA. (Photo courtesy of Leigh Thwaites

Figure 3: Pivoting carp screen adjustment at Ramco SA. (Photo courtesy of Leigh Thwaites

Findings: The current CES designs and management regimes were noted to have been ineffective in reducing the numbers and biomass of Carp in wetlands.

A diverse and abundant native fish community (14 species) was found to utilise wetlands and wetland inlets. Some existing exclusion screen designs are detrimental to native fish (by excluding most sizes and life history stages), including species of conservation significance. Other aquatic fauna, such as turtles, are also likely to be impacted.

Two types of screens that will optimise the exclusion of large, sexually mature carp were designed:

  • A square grid mesh with 44 mm gaps
  • A “jail-bar” design with 31.4 mm gaps.

The jail bar design was found to collect less debris, trap more Carp and less native fish, and had little effect on flow velocity.

Lessons learned and future directions:CES may be beneficial as part of an integrated Carp management regime in some wetlands. Presently, there is no benefit in using CES in permanently inundated wetlands, unless other Carp reduction measures are also employed.

  • The use of CES alone should be considered for use at seasonal/ ephemeral wetlands that dry every 1-2 years. They may also be suited to permanent shallow wetlands that remain filled for >2 years at a time, if it can be shown that all adult Carp migrate from wetlands to overwinter in deeper river water.
  • The jail bar CES with 31 mm apertures between bars screen passed more native fish, including the greatest proportion of Bony Herring (Nematalosa erebi) (>90%), which are the key large-bodied native fish found to use wetlands and wetland inlets.
  • All CES need to be regularly maintained to ensure that they are functioning as intended and are not altering channel hydrodynamics or impeding the passage of native fauna.

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.

Contacts: Dr Leigh Thwaites, South Australian Research and Development Institute. Tel: + 61 8 8207 5495, Email: leigh.thwaites@sa.gov.au.

Link: Not yet published.

Carp Separation Cages

Key words: Introduced fish, Pest fish, Carp, Carp Cage, Native Fish Strategy

Fishways facilitate movement of both native and non-native fish and thus provide species such as carp with a significant opportunity to migrate and disperse upstream. Common Carp (Cyprinus carpio, henceforth referred to as Carp) are highly migratory and often dominate the biomass utilising fishways. A carp separation cage (CSC) is a specially designed trap, usually installed on infrastructure such as a fishway, that takes advantage of the jumping behaviour of migrating Carp by drafting them into a holding cage for later removal, while allowing native fish to continue swimming upstream.

Broad aim: The aim of this project was to develop low cost technology to automatically separate adult carp from native fish, and to identify the season, time(s) of day, environmental cues and biomass of adult and juvenile Carp migrating in fishways to better target the use of the technology.

Methods: Two versions of the CSC were trialled within a straight section of a channel near a fishway at Torrumbarry Weir on the middle reaches of the Murray River about 1630 km from the Murray mouth. A design was first trialled requiring manual operation, with on-site weir keepers checking for fish every 24 h. Fish were removed daily. A second automated design was later trialed incorporating a mechanical counterweight system to automatically crowd and release non-jumping fish via a lifting false floor and native fish exit gate. A cage was placed at the exit of the fishway to trap, count, and measure all fish that exited the crowding system.

Carp being harvested from a Carp cage. (Photo by Ivor Stuart)

Figure 1. Carp being harvested from a Carp cage. (Photo by Ivor Stuart)

Findings: The prototype CSC demonstrated that large numbers of Carp can be removed with minimal catch of native fish. However, the need to manually release any trapped native fish limited the application of the technology, especially in remote areas. Subsequent versions of the initial design resulted in several improvements, including:

  • being able to operate on the exit of any fishway type (Denil, vertical-slot, lock);
  • an increase in the biomass of Carp and native fish that can be held;
  • trapped fish can be held in lower water velocity conditions;
  • native fish are exited into the weir pool rather than into the fishway;
  • the cage is now more transferable among exits or different fishways; and
  • access and removal of Carp is more efficient.

Lessons learned and future directions: This study highlighted the opportunity to utilise fishways to remove Carp. The CSC should be targeted to periods of strong carp movement. Spring is a critical time for native fish movement and utilising the technology outside the spring period will maximise catches of Carp but minimise disruption to native fish movements.

For both monitoring and Carp removal purposes it is essential that trap construction, fishway trapping and data collection are standardised across the many locks and weirs of the Murray River.

A commercial trial of the CSC in the fishway at Lock 1 (Blanchetown) has been underway for some years.  From 2007-2011, 300 tonnes of Carp have been harvested.

The CSC has also been modified to suit Carp separation at wetlands.

Carp cage installed at Turrumbarry. (Photo by Ivor Stuart)

Figure 2. Carp cage installed at Turrumbarry. (Photo by Ivor Stuart)

Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy and undertaken by Ivor Stuart, Alan Williams, John McKenzie & Terry Holt from the Arthur Rylah Institute  and Goulburn Murray Water.

Contact: Arthur Rylah Institute, 23 Brown St, Heidelberg, Victoria, Australia, +61 3 9450 8600.

Link:

http://www.finterest.com.au/wp-content/uploads/2013/07/MD218%20Carp%20separation%20cage%20MkIII%20&%20Mk%20IV.pdf

http://www.finterest.com.au/wp-content/uploads/2013/07/R2104%20Separation%20cages%20for%20for%20removal%20of%20carp.PDF

Examination of options for removal and disposal of Carp from fishways along the Murray River – including the Williams’ Carp Separation Cage

Key words: European carp, ethical disposal, pest fish, fishways, Native Fish Strategy.

The introduced fish species Common Carp (Cyprinus carpio) has been shown to impact on native fish in many ways, including through direct predation as well as competition for resources such as food, shelter and breeding sites. The “Sea to Hume” fishway program has seen the construction of fishways at sites along the Murray River from the tidal barrages to Hume Dam. While the primary aim has been to improve migration of native fishes, the fishways also facilitate the passage of Carp, potentially providing access to upstream habitats (including spawning habitats) for large numbers of this alien species (Fig 1). The Williams’ Carp Separation Cage is designed to offer a way of removing Carp from fishways without significantly impacting on migrating native fishes.

This research project set out to examine issues and options associated with harvesting Carp at fishways along the Murray River. The study looked at options for harvesting Carp at fishways along the Murray River with an emphasis on the use of the Williams’ Carp Separation Cage (Fig 2), together with the ethical and logistic issues associated with the disposal of Carp.

Carp can reach quite high abundance below barriers to migration such as dams and weirs.  (Photocourtesy of Leigh Thwaites, SARDI.)

Figure 1. Carp can reach quite high abundance below barriers to migration such as dams and weirs. (Photo courtesy of Leigh Thwaites, SARDI.)

How the options were examined: The project team reviewed available literature on methods for the collection and removal of Carp. Design constraints and factors affecting performance were considered, as were recommendations made to enhance functionality and effectiveness. Input from each jurisdiction was considered (to determine capacity and willingness to implement collection programs) as were markets for both human and industrial use (including processing requirements and logistics).

Results:

  • The Williams’ Carp Separation Cage was found in most instances to be the preferred method of harvesting Carp. Other methods such as trapping, netting or electrofishing below a weir were considered to have merit for further consideration where the high biomass of Carp may physically impact on migratory native fishes.
  • Harvesting should focus on the migration of pre-spawning adult Carp (about August to December).
  • Disposal methods should favour those that utilize Carp as a resource.
  • While the engagement of commercial fishers is desirable, the commercial Carp fishery is only marginally viable, especially in NSW. It is likely that the involvement of commercial fishers beyond high density sites will have to be subsidized or a coordinated program of collection and storage (e.g. freezers) will need to be implemented.
  • Other options need to be investigated including burial, cremation and composing.
  • Carp must be euthanased in an ethical manner. Currently accepted techniques include the use of anaethetics although with large numbers of fish an ice slurry may be the only practical method. The report also recommends trialling commercially available percussive stunning machines.

A report was produced at the end of the project (Jackson, P. (2009). Final report for River Murray Water, Murray-Darling Basin Authority). This recommends rolling out a coordinated program to harvest Carp along Murray River fishways by expanding first within SA, based on the Lock One experience, and then into NSW. Harvesting should focus on priority sites where high numbers of Carp are present and where fishways will allow access to preferred Carp habitat and potential breeding sites.

The Williams Carp Separator cage provides a potential means for harvesting of Carp at fishways along the Murray River. (Photo courtesy of Ivor Stuart.)

Figure 2. The Williams’ Carp Separation Cage provides a potential means for harvesting of Carp at fishways along the Murray River. (Photo courtesy of Ivor Stuart.)

Take home messages: There is significant potential to harvest Carp at Murray River fishways using the Williams’ Carp Separation Cage but it must be undertaken without any significant impact on native fish migration. A coordinated program with an appropriate level of monitoring is required. The monitoring should include assessments of the impacts of Carp harvesting on upstream Carp populations and recruitment.

Ethical euthanasia of Carp and cost effective disposal remain issues but there are potential solutions. Approval should be sought from relevant Commonwealth agencies for the use of practical destruction measures such as ice slurries and trials using percussive stunning devices should be undertaken. Trials should also be undertaken using commercially available composting bins at sites where commercial fishing is not viable.

Stakeholders and Funding bodies: This research project was funded through the Murray-Darling Basin Authority’s River Murray Assets Division and carried out by consultant Dr Peter Jackson.

Contact: Dr Peter Jackson, Consultant, +61  7  5429 2276+61  7  5429 2276,  Email Peter.Jackson@westnet.com.au

From Rainforest to Oil Palms and back again: a Daintree Rainforest Rescue in far north Queensland

Robert Kooyman, Joe Reichl, Edie Beitzel, Grant Binns, Jennifer Croes, Erryn Stephens, and Madeleine Faught

The establishment of Oil Palm (Elaeis guineensis) plantations is responsible for massive rainforest clearing and destruction throughout the tropics of Southeast Asia and beyond, and has captured the attention of conservation organisations around the world. One such organisation is Rainforest Rescue (RR), a not for profit Australian based conservation NGO. Through local and international projects (including in the Daintree region of Australia and Sumatra in Indonesia) RR has undertaken conservation actions that include removal of Oil Palm plantations to re-establish rainforest close to National Park areas.

The rainforest of the Daintree region provides an active window into the evolution, biogeography, and ecology of the southern (Gondwanan) rainforests, and their interaction with Indo-Malesian floristic elements. It has many (ca. 120) federal- and state- listed Threatened, Vulnerable, Of Concern, and Rare plant and animal species and a range of rainforest types.

To achieve restoration of a small (27.6 ha) but important piece of the global distribution of lowland tropical rainforest, RR purchased Lot 46 Cape Tribulation Road in the Daintree area of far north Queensland, Australia in 2010 and, in 2012, secured funding to set the property on its long journey back to rainforest.

The property was partly cleared in the 1960s, first for cattle grazing and later for Oil Palm cultivation. It has a mix of cleared (ca. 11 ha) and early stage natural regeneration (ca. 10ha) areas, bounded on two sides by more intact and mature rainforest (ca. 7 ha). Soils are mostly free-draining sandy clay loams on flat terrain

The on-ground works.  The property was divided into five working Zones as part of the restoration planning process (Fig. 1). Because of a nearby large seed source forest a key objective of the project is to maximise and protect natural regeneration, as well as planting larger openings. Up to 30,000 trees representing 100 species are expected to be planted during the 2-year life of the project, with around 10 ha of natural regeneration interspersed.

Figure 1. Map showing property, work zones (ZONE 1-5), permanent photographic points (Photo point 1-9), location of planting trials (Zones 1 and 2), and primary weed control area (2013) in orange. (Courtesy Google Earth)

Figure 1. Map showing property, work zones (ZONE 1-5), permanent photographic points (Photo point 1-9), location of planting trials (Zones 1 and 2), and primary weed control area (2013) in orange. (Courtesy Google Earth)

Trial tree plantings were undertaken in early 2011 and 2012, and selective weed management (herbicide based grass and soft weed control) began at the same time to optimise natural regeneration prior to identifying and preparing suitable planting sites.

Plantings.  The planting trials were each one hectare in area and designed to test the efficacy of two different high diversity (60-90 species) planting designs. In Zone 1 tree spacing was 2.5m, and in Zone 2 the spacing was 1.5m. Seedlings for rainforest plantings were propagated and grown in the RR nursery in the Daintree lowlands. Seed collection was undertaken north of the Daintree River and included seed collected from the property. A low number of vines were included in the species mix for subsequent plantings.

A total of 90 species have been planted to date. The species mix included some early stage (pioneer type) tree species from genera such as Polyscias (Araliaceae), Alphitonia (Rhamnaceae), Macaranga (Euphorbiaceae) and Commersonia (Malvaceae); and tall fast growing species such as Elaeocarpus grandis (Elaeocarpaceae) and Aleurites moluccana (Euphorbiaceae). The remaining species represented mostly moderately fast growing species, and some slower growing mature phase rainforest species.

Weed control. Where possible, large Oil Palms were removed mechanically, but to protect existing rainforest regeneration many required stem injection with herbicide. Several methods are currently being trialled to determine the most time and cost effective approach to controlling this large and difficult weed.

Late in 2012 and early in 2013 extensive mechanical and chemical weed control was undertaken in Zones 3, 4 and 5 (Fig. 1). This included mechanical clearing of large areas dominated by Giant Bramble (Rubus alceifolius) and other weeds, and some mechanical removal of Oil Palm seedlings on the southern side of the creek that traverses the property (Zones 3 and 4). Follow up chemical control (systematic backpack spraying of glyphosate) was conducted immediately (as required) to complete the site preparation for planting. This was targeted at grasses, broad-leaf weeds, and regrowth of woody weeds.

Monitoring design. Monitoring plots (7 / 50 x 20m plots, each with 10 / 10 x 10m subplots) and permanent photographic points (12 in total, 7 in association with monitoring plots) were established in the five working Zones. Cover, number of species and density will be recorded in these plots at each stratum at 12 month intervals. One monitoring plot was established in each of Zones 1 and 2, three in Zone 3 (including directly adjacent to Zone 4), and two in Zone 5 (in the north of the property; yet to be measured). Zone 4 will be monitored visually and by photo point as it is mostly natural regeneration enhanced by weed control.

Preliminary Results. The first round of project monitoring (year 1 establishment) provided base-line information for future development of the plantings and natural regeneration through assessing canopy cover, leaf litter cover, and a range of other factors that will change over time (Table 1). Informal observations have shown that site dominance was achieved by the trees planted 12 and 18 months ago in Zones 1 and 2.  Substantial numbers of wildling seedlings (of up to 11 species in a plot; and 15 in total) were found in the sites monitored prior to more recent planting.

Mechanical weed control was reported to be extremely effective and the operator was able to minimise damage to existing regrowth of species such as Melicope elleryana (Rutaceae), Glochidion harveyanum var. harveyanum (Phyllanthaceae), Macaranga involucrata var. mallotoides (Euphorbiaceae), Polyscias australiana (Araliaceae), Rhodamnia sessiliflora (Myrtaceae), Alphitonia incana (Rhamnaceae) and Aidia racemosa (Rubiaceae). In combination with the early implementation of broad and targeted spraying this maximised the retention of substantial existing saplings and seedlings.

Project funding will cease in 2014, and control of all weeds and rainforest establishment is expected to be completed in 2015; with only minor weed control required thereafter once canopy cover is established. Monitoring will continue at 12 month intervals and inform future publications.

Acknowledgements: The project is dependent on the generous support of RR donors and the on-going efforts of RR staff in FNQld. Funding for the project was provided by a Federal Government Biodiversity Fund Grant.

Contact:  Robert Kooyman, National Herbarium of NSW, Royal Botanic Gardens and Domain Trust, Mrs Macquaries Road, Sydney 2000 Australia.   Email: robert@ecodingo.com.au;

Figure 2 Mechanical weed control in Zone 3 (January 2013) prior to planting. Note remaining natural regeneration.

Figure 2 Mechanical weed control in Zone 3 (January 2013) prior to planting. Note remaining natural regeneration.

Figure 3. Newly planted trees in Zone 3 (March 2013). Note surrounding natural regeneration.

Figure 3. Newly planted trees in Zone 3 (March 2013). Note surrounding natural regeneration.

Figure 4. Zone 2 planting trial established in late 2011 at 18 months. Tree spacing at 2 - 2.5m.

Figure 4. Zone 2 planting trial established in late 2011 at 18 months. Tree spacing at 2 – 2.5m.

Table 1.  Synthesis of baseline data for natural regeneration, and progress (including planting) up to February 2013 measured on (50 x 20m) permanent monitoring plots (PP), in Zones (1,2,3), by Themes (1 – planting; 2 – natural regeneration). PD – total planted diversity on plot; PS(n) – number of seedling planted on plot; WS – wildling seedlings (0.5-1m in height); WD – wildling diversity; Av. CC(%) – Average Canopy Cover (%); Av. L(%) – Average Litter Cover (%); Av. LBC(%) – Average Log-Branch Cover (%); Av. PCHt – Average planted canopy height (m); dbh – diameter at breast height (1.3m); NR – Number of stems, natural regeneration >1cm DBH; NR-div – Diversity of natural regeneration >1cm DBH; Age (mths) – Age of planting in months. Zone 4 (not shown) has permanent photo points and visual monitoring.

PP Zone Theme PD PS(n) WS WD Av.CC(%) Av.L(%) Av.LBC(%) Av. PCHt NR NR-div Age(m)

1

3

1, 2

82

424

236

7

27.5

52

7

0.6 – 1

218

12

1

2

3

1, 2

0

0

587

11

41

61.5

6.7

NA

248

11

0

3

3

1, 2

0

0

133

5

18.5

48.8

4.6

NA

109

9

0

4

2

1

85

390

45

7

13

30.6

3

1-2m

45

5

12

5

1

1

85

207

95

5

45.5

58

5

2-3m

48

7

18

Appendix 1 List of main weed species located and treated on the property.

Common Name Species Family Life Form
Sanchezia Sanchezia parvibracteata Acanthaceae herb
Brillantaisia Brillantaisia lamium Acanthaceae herb
Goosefoot Syngonium podophyllum Araceae vine
Toothed Philodendron Philodendron lacerum Araceae climber
Oil Palm Elaeis guineensis Arecaceae palm
Dracaeana Dracaeana fragans Asparagaceae small tree
Sensitive Plant Mimosa pudica Fabaceae creeper
Calopo Calopogonium mucunoides Fabaceae creeper
 Green Summer Grass Urochloa decumbens Poaceae grass
Giant Bramble Rubus alceifolius Rosaceae scrambler
Snake Weed Stachytarpheta cayennensis Verbenaceae herb