Author Archives: emrprojects

Evaluating use of chemical marking in monitoring stocked fish

Key words: fish tagging, fish marking, chemical marking, stocking effectiveness, Native Fish Strategy

More than three million native fish are produced in private and government hatcheries and stocked into waterways of the Murray-Darling Basin each year. To date, little has been known of the fate of stocked fish or their impact on wild populations, in part because of a lack of suitable methods for marking small juvenile fish. The increasing use of wild fish populations as indicators of river ‘health’ was also potentially compromised by the inability to distinguish between hatchery-bred and wild fish.

Objectives and methods: A sequence of projects funded through the Native Fish Strategy sought to develop techniques for marking hatchery bred fish.

Three marking methodologies were trialled and developed using Golden Perch (Macquaria ambigua) as the model fish species:

  • Osmotic induction marking of fingerlings (which enhances uptake of the marker chemical by immersing fish in a 5% saline solution) with alizarin red S and calcein. (Figs 1 and 2)
  • Marking of otoliths (ear bones) via immersion of fingerlings in enriched stable isotopes of strontium and barium.
  • Transgenerational marking of otoliths through the injection of enriched stable isotopes of barium into maternal broodfish

The feasibility of each of the methods was examined with particular emphasis on practicality and economic considerations for government and private hatcheries.

A range of experiments were conducted to investigate marking effectiveness, assess the influence of immersion times and chemical concentrations on mark intensity, and test for impacts of marking on growth and mortality. Experiments were also conducted to assess whether enriched stable isotopes could be used to induce multiple unique marks, which could then be used as batch marks.

Consultation took place with the Australian Pesticides and Veterinary Medicines Authority (APVMA) and Food Standards Australia New Zealand (FSANZ) to seek clarity on whether marking constituted use of a veterinary chemical product, and the legality of their use in fish that may eventually be consumed as food.

Field-based experiments were undertaken to assess the contribution of stocked fish to fish communities sampled in a number of rivers. Experimental stocking and subsequent fish community surveys took place in the Murrumbidgee River, Edward River and Billabong Creek. The Murray River between Yarrawonga and Tocumwal was also surveyed as an unstocked reference site. Stocked fish were either marked with alizarin complexone or calcein, or were confirmed as stocked fish using otolith chemistry analyses. Electrofishing surveys in experimental and control river reaches enabled assessment and comparison of the contribution of stocked fish to fish communities sampled. 

Figure 1. A calcien marked fish head under natural light. Photo courtesy of Arthur Rylah Institute.

Figure 1. A calcien marked fish head under natural light. Photo courtesy of Arthur Rylah Institute.

Figure 2. A Golden perch fingerling newly marked with calcein. (Photo courtesy of Arthur Rylah Institute.)

Figure 2. A Golden perch fingerling newly marked with calcein. (Photo courtesy of Arthur Rylah Institute.)

Findings: Each of the methods was found to have strengths and weaknesses. Techniques that only marked otoliths (i.e. stable isotopes) require the fish to be killed and the otoliths analysed in a laboratory to determine whether they are marked. However alizarin and calcein leave external marks that can be detected in the field without having to sacrifice the fish, a distinct advantage for most river health monitoring programs or projects involving threatened species.

A field detection kit for calcein marks was developed which included a field fluorometer for quantitative measurement of calcein fluorescence and a specialised torch and glasses set for visual identification of marked fish.

Investigation revealed that there were no registration requirements for any of the marking techniques and chemicals, and that the chemical marking techniques developed during the project can be legally applied in hatcheries provided specific processes are undertaken.

The results of the field stocking experiments showed that at least a proportion of the stocked fish survived to reach the legal minimum size in all three rivers. However, the impacts of stocking on population structure were very different among rivers. In the Edward and Murrumbidgee Rivers, the age classes corresponding to the years of stocking were comprised of 18-38% experimentally stocked fish, and these fish made only a relatively minor contribution to the total catch of Golden Perch. In contrast, stocked fish comprised up to 100% of age classes in Billabong Creek and stocking resulted in a four-fold increase in the catch rates of Golden Perch.

Lessons learned and future directions: Osmotic induction marking with calcein had no detectable effects on fish health and was found to be relatively quick and easy – taking only 15 minutes to mark up to 20,000 fingerlings. The simplicity and cost-effectiveness of osmotic induction marking make it feasible for widespread adoption in hatcheries.

Large-scale calcein marking of hatchery fish commenced in 2009, and agencies from all State and Territory jurisdictions within the MDB have initiated processes to incorporate calcein marking into their stocking and/or research programs. The results of the experimental stocking study demonstrate that stocking has the potential to strongly affect population structure and abundance of the stocked species.

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

Developing a population model for Murray Cod (Macculochella peelii) to address key management actions

Key words: Population model, Murray Cod, fisheries management, Native Fish Strategy

Threats and Impacts: Murray Cod (Macculochella peelii) is a key recreational fishing target species as well as being a nationally listed threatened species (Fig 1). Management action is required to rehabilitate populations of this species in the Murray-Darling Basin. Fish population models are a simple description of a fishes life cycle and try to incorporate any external factors that may affect the individual and population. The main use of these models is to hypothetically assess the impacts (negative or positive) of different management or environmental scenarios to provide managers with predictive power to better manage fish populations. Prior to this project no such model had been created for any species in the Murray-Darling Basin.

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

  • Develop a computer model (or models) to represent the population dynamics of Murray Cod under alternative management options.
  • Develop various management scenarios in relation to size and bag limits and potential recovery times from overfishing, fish kills and other management or environmental scenarios which may affect Murray Cod populations.
  • Document the findings of this work, and the implications for developing management options for Murray Cod and the research on Murray Cod biology and ecology required for improving the model (or models).

Methods: A review was undertaken initially to summarise relevant scientific, management, angler and aquaculture literature on:

  • Murray Cod biology and ecology;
  • Management options for Murray Cod and similar fish in the Murray-Darling Basin and elsewhere; and,
  • Population and other (climate and GIS) models for fish or other fauna which will allow alternative management options to be tested;

Conceptual models of Murray Cod biology and ecology were then developed, and information gaps which needed to be addressed were identified. A workshop was also held to bring together a range of technical experts and jurisdictional representatives (SA, QLD, VIC, NSW, ACT and Commonwealth) to determine the key management actions to address the sustainable management of Murray Cod as well as the knowledge requirements necessary to develop the appropriate model(s) to assess the key management actions.

A population model for Murray Cod was developed as a key output of this project, which would enable different management actions/scenarios to be assessed and compared on the basis of their relative benefit and level of risk.

Figure 1 - This project developed a population model for Australia's largest freshwater fish species, Murray Cod . (Photo courtesy of Jamin Forbes)

Figure 1 – This project developed a population model for Australia’s largest freshwater fish species, Murray Cod . (Photo courtesy of Jamin Forbes)

Figure 2 - An example of graphical outputs from a fishing scenario. (Courtesy of Charles Todd.)

Figure 2 – An example of graphical outputs from a fishing scenario. (Courtesy of Charles Todd.)

Findings: Modelled management scenarios for Murray Cod indicate that the risk to populations can be reduced substantially by appropriate changes to the size limits on angler take. The  implementation of a slot size (minimum and maximum size limit) that protects both smaller and larger fish reduced population risk considerably. While habitat changes are difficult to quantify, it was illustrated that reductions in amount of habitat can place additional risk on populations, particularly when combined with angler take. Importantly, the collective impacts of less recognised threats such as thermal pollution, fish kills and mortalities to larvae over weirs and losses into irrigation off-takes can be explored and need to be recognised as having the potential to contribute significantly to mortalities at certain sites.

Lessons learned and future directions: The methods outlined in this study offer a formalised, rational, modelling approach that can form the basis for the assessment and prioritisation of management options for Murray Cod to minimise the risk to populations. Such modelling also highlights data gaps and monitoring requirements and can become an integral part of the conservation and fishery management process (Fig 2) and provides a tool for exploring the outcomes of management scenarios at both the regional and local scale. The modelling process has helped facilitate interagency Murray Cod management and emphasises the need for coordination between fishery managers and water/environmental protection/conservation agencies.

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

Contact: Dr. Charles Todd, Arthur Rylah Institute, (02) 60519920, Charles.Todd@depi.vic.gov.au, 23 Brown St, Heidelberg, Victoria, Australia, +61 3 9450 8600.

Link: http://www.mdba.gov.au/sites/default/files/pubs/MC-Final-Report.pdf

Counting Murray-Darling fishes by validating sounds associated with spawning

Key words: fish counting, spawning, Murray-Darling Basin, Native Fish Strategy

Over 700 fish species worldwide produce sounds, and the unique sounds made by fish species can often detected using underwater microphones. Most sounds are produced during courtship, for communication or identification, and they can be useful if attempting to locate fish, make abundance estimates, or direct habitat management. Prior to this project however, there had been little consideration given to use of sounds produced by fish for these purposes in Australian rivers.

Broad aim and methods: The specific objectives of this project were:

  • To trial a bioacoustic (fish noises) technology to determine whether captive large-bodied native fish (Murray Cod (Maccullochella peelii), Golden Perch (Macquaria ambigua), and Silver Perch (Bidyanus bidyanus) produce sounds associated with artificial or pond spawning, and whether spawning population counts can be obtained.
  • To isolate individual spawning sounds produced by each fish species and its associated behaviours, for example, do individual species produce unique, distinguishable sounds for male dominance, courtship, spawning or distress?
  • To test for soniferous sounds in wild collected adult carp spawned in captive conditions.
  • To scope passive bioacoustics as a tool for measuring the relative abundance of fish in key habitats and potentially in fishways.

 A series of trials were undertaken initially to benchmark or sound truth ambient noises within the experimental environment. In an initial trial, a hydrophone was placed into a tank with no fish to record noises. A second trial involving the same procedure but with a single fish was undertaken. The final experimental phase was to benchmark the noises from a number of fish (mixed sexes) Four fish that had been injected with hormones (two male and two female) were placed into a tank and recorded for 24 hours (Figs 1 – 2). A DIDSON camera was also set up to provide vision of the spawning fish.

Figure 1 - A sonogram of acoustic signals recorded in a tank with spawning Golden Perch. The noise could not be specifically isolated to the fish. (Courtesy of Ivor Stuart)

Figure 1 – A sonogram of acoustic signals recorded in a tank with spawning Golden Perch. The noise could not be specifically isolated to the fish. (Courtesy of Ivor Stuart)

Figure 2 - Researcher Jonothan Doyle listening to fish. (Photo courtesy of Ivor Stuart)

Figure 2 – Researcher Jonothan Doyle listening to fish. (Photo courtesy of Ivor Stuart)

Findings: Several acoustic noises were isolated during the project and although these were absent from the controls they could not specifically be attributed to the fish. These results demonstrate that some Murray-Darling Basin native fish potentially produce noises. Further research and replication is needed to clarify the mechanism of fish sound production, individual variation in vocalisation and the utility for research and management. The sonogram data did appear to include biological noise, but the DIDSON camera proved unsuitable in hatchery tanks and further work with fixed video cameras is needed to link sound production with fish behaviour.

Murray Cod appear to provide a model species for further acoustic trials as these fish have complex social behaviour that can be observed in the semi-natural conditions of a hatchery pond. The suggested protocol is to set up a DIDSON camera or video recorder and hydrophones within the spawning drum (used by fish as a laying site). This method would allow visual confirmation of fish making noises, and the hydrophone would be placed in an optimal position to capture any vocalisations.

Lessons learned and future directions: The preliminary results of this project suggest that using a hydrophone to detect native fish is plausible, but requires further work. If further trials are successful this technology would be useful for detecting native fish spawning which would be used to determine fish habitat preferences for both conservation and rehabilitation. 

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

Contacts: Ivor Stuart, Kingfisher Research P/L.,0408 619 126, ivor.stuart@gmail.com

Link: http://www.mdba.gov.au/sites/default/files/pubs/MDBA-13088-Soniferous-Reportv2.pdf

Assessment of a potential to develop population models for priority species in the Murray-Darling Basin

Key words: population models, native fish, Murray-Darling Basin, Native Fish Strategy

Threats and Impacts: Native fish of the Murray-Darling Basin (MDB) have experienced severe contractions since European settlement. Gaining greater insight into the population dynamics of native fishes is critical for long-term conservation. Population models play an important role in identifying underlying factors that may affect population structure and the persistence of species.

Broad aim and specific objectives: This study aimed to assess the potential development of population models for priority species in the MDB and provide an indication of the use of these types of models in natural resource management. 

An initial review of the available literature was undertaken to assess the degree to which populations models developed for Australian freshwater fishes have been adopted to inform decision making by managers or guide data collection and research directions.

A survey was undertaken of fish and fishery managers to identify species of interest. A further survey of managers and researchers provided information on data availability for these species. For each species of interest, a life cycle model was developed to help identify the data required to develop a population model. This process, in conjunction with the information gathered from mangers and researchers and information already available in the literature, identified key knowledge gaps to help guide future research and data acquisition for developing a deeper understanding of population dynamics.

Findings: A review of population models in natural resource management raised a number of concerns in relation to the ability to get appropriate information from the primary literature. The review did also find good examples of where population models have integrated into management and policy, mainly in a fishery context. There are some examples where models have influenced management and policy development in freshwater research such as the trout cod model. Although the review found there was strong interest in the development of models, there needs to be a concerted effort from all interested parties to ensure models are used to influence policy and management outcomes and utilised by the intended stakeholders.

This study also surveyed a number of fish and fishery managers in the Murray-Darling Basin to establish a list of fish species of most concern. Twenty five species were recorded as of most concern and these were scored for priority. A further survey of scientists and managers was conducted to assess data availability that could be used in a model similar to that developed for Murray Cod (Maccullochella peelii). Of the twenty five species reviewed, there was sufficient life cycle information to construct an age population model and data that could be used to estimate the parameters required for an age structured model for eight species (in order of concern with rank number): Silver Perch (Bidyanus bidyanus) (1st); Macquarie Perch (Macquaria australasica) (2nd); Trout Cod (Maccullochella macquariensis) (4th); Murray Hardyhead (Craterocephalus fluviatilis) (6th); Golden Perch (Macquaria ambigua) (7th); Two-spined Blackfish (Gadopsis bispinosus) (14th); Carp (Cyprinus carpio) (17th); Brown Trout (Salmo trutta) (23th); and while no data was held in Australia for Rainbow Trout (Oncorynchus mykiss) (12th), sufficient data is available in the international literature to estimate the required parameters for an age based population model. As a priority, it was recommended that models be developed for the five species ranked in the top 10 of species of most concern: Silver Perch, Macquarie Perch, Trout Cod, Murray Hardyhead and Golden Perch.

It was also recommended that research be undertaken on the five other species of concern in the top 10, for which there is insufficient information to construct a model, to improve knowledge and/or data to the model development level and consider model development for these species. 

Figure 1 - Silver Perch was identified as a species for which a population model could be developed, and would be valuable. (Photo courtesy of Jamin Forbes)

Figure 1 – Silver Perch was identified as a species for which a population model could be developed, and would be valuable. (Photo courtesy of Jamin Forbes)

Figure 2 - This study highlighted value of using data on Trout Cod to inform an age structured population model. (Photo courtesy of Jamin Forbes)

Figure 2 – This study highlighted value of using data on Trout Cod to inform an age structured population model. (Photo courtesy of Jamin Forbes)

Lessons learned and future directions: The study has highlighted a short list of native species, which as a priority require population modelling to provide better guidance for future management actions (Figs 1 and 2). Better-targeted management actions will provide increased benefits for native fish populations on a benefit per resource basis. The highlighted species where insufficient data is available to construct population models provide researchers with a shortlist of priority research questions and should better focus attempts at filling knowledge gaps for native fish species of the MDB. 

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

Contact: Dr. Charles Todd, Arthur Rylah Institute, (02) 60519920, Charles.Todd@depi.vic.gov.au, 23 Brown St, Heidelberg, Victoria, Australia, +61 3 9450 8600.

Link: http://www.finterest.com.au/wp-content/uploads/2013/07/MD1179%20Population%20modelling%20scoping%20study.pdf

Audit of water quality problems arising from land use in the Murray-Darling Basin

Key words: water quality, audit, land use, Murray-Darling Basin, Native Fish Strategy

Aims: This is one of a suite of early projects under the Native Fish Strategy (NFS) that sought to scope the issues and information gaps that the NFS would need to address.  Specifically, this project aimed to: :

  • collate data, identify and map regions , landscapes, land uses and industries that are important causes of water quality (WQ) problems in the Basin (e.g. Fig 1)
  • Determine a meaningful scale/accuracy for reporting based on available data and quantitatively report on land use (distributed and point source) contributions to WQ problems on a third order catchment basis.
Figure 1 - this project sought to collate data on land uses and industries which are important causes of water quality problems. Photo courtesy of Arthur Mostead.

Figure 1 – this project sought to collate data on land uses and industries which are important causes of water quality problems. (Photo courtesy of Arthur Mostead.)

Methods: This project was essentially a desktop review and Geographic Information System data atlas formation exercise that included: developing a classification of land uses/management practices in relation to WQ impacts; identifying existing relevant datasets and projects; evaluating available data for relevance and identify gaps; reporting the findings for a pilot catchment (the Broken River/Creek catchment in Victoria). Mapping was available at a range of scales.

There is a wide range of physical, chemical ecotoxicological and ecological parameters that can be used to provide information on WQ, but no single measure of overall WQ. The WQ parameters selected for the study were considered to have direct effects on native fish as well as direct effects on habitat suitability, food sources as well as fish behaviour and ability to migrate and reproduce. Water quality parameters considered of major importance in the study were temperature (cold water); turbidity, dissolved oxygen, and nitrogen/ammonia. Parameters of moderate importance were salinity, pH, toxicants, and pathogens. Land use has known relationships with the nature of WQ changes that occur as a result of that land use (e.g. mining and acid water drainage), and similarly there are known relationships between point source discharges from particular industries and WQ. A matrix of relationships between land use/point source discharges and the nine WQ parameters informed a spatial model that also included a risk assessment of the likelihood and consequence of a critical WQ impact occurring, including the location of high priority native fish sites (species/habitats/refuges). 

The methodology devised for the project was designed to:

  • Facilitate ease of access and use of a complex array of land use and WQ related datasets
  • Display the data so that it can be used by managers responsible for native fish and their habitat
  • Recognise important WQ parameters for native fish in the Basin
  • Provide insight into areas of the Basin under threat from WQ changes with respect to native fish, and
  • provide a predictive yet easy to understand and utilise spatial model.

Findings: The spatial model when applied to the Broken River catchment with land use mapped at ≤1:100,000 scale clearly identified spatial areas that were at risk of WQ impacts, and the level of the risk involved (low, moderate, high extreme). When compared with land use mapped at the 1:250,000 scale, the coarser scale of mapping led to errors in assessment of risk of WQ impacts. Consequently, the spatial model was not recommended to be used for specific catchment investigations where land use was captured at scales >1:100,000. While the limitations of 1:250,00 scale land use capture are acknowledged, analysis using such data may provide useful information to focus further investigations. Consequently the spatial model was applied across the entire Basin at the 1:250,000 scale and indicated the following catchments had the most land use area with high potential to cause water quality impacts that may affect native fish: Gwydir, Namoi, Murray (Hume Dam to SA Border), Murrumbidgee, Loddon, Broken, Goulburn and Campaspe. 

Lessons learned and future directions: The spatial model provided a useful tool for managers to investigate and visualise areas at risk of WQ impacts to native fish. The ability of the model to discriminate such areas at risk at a specific catchment scale declined above scales of 1:100,000 for land use mapping. The lack of detailed information on fish tolerances to various WQ parameters hampers the precision of the model. Similarly the scarcity of spatial data on WQ and the lack of readily available spatial data for fish distribution was a significant issue.

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

Contact: Earthtech, +61(7) 3343 3166

Link: http://www.mdba.gov.au/sites/default/files/archived/mdbc-NFS-reports/464_execsum_audit_WQproblems_draft.pdf

Management of genetic resources within the Murray-Darling Basin

Key words: Murray- Darling Basin, fish, genetic diversity, genetic resources, Native Fish Strategy.

The Native Fish Strategy aims to rebuild all fish stocks within the Murray-Darling Basin (MDB) to 60 percent of pre-European settlement levels within 50 years. To achieve this target, management responses would be assisted by an understanding of the underlying genetic diversity of species. Many species have genetically distinct populations. For example, Murray Cod (Macculochella peelii) are known to have little genetic difference throughout most of the southern range of the MDB, however, several populations (Lachlan, Macquarie and Gwydir catchments) were found to be genetically distinct.

Maintaining genetic diversity is critical to species and ecosystem resilience, particularly in the face of changing environmental conditions. Despite the explicit recognition within legislation that genetic diversity is a key component of biodiversity, until now there remains no consistent or practical guidelines for the management of these resources.

Project objectives and methods: The objectives of this project were to create a resource able to be used to guide the management of genetic diversity within the Basin.

Specific objectives:

  • Review current genetic management practices across the MDB;
  • Review the current knowledge base for genetic structure within native fish species in the MDB and identify knowledge gaps;
  • Hold an international workshop to define the level of genetic management required to maintain distinct evolutionary significance of native fishes within the MDB;
  • Suggest a consistent approach to the management of genetic resources for native fish in the MDB.

A survey of fisheries agencies was conducted to identify current genetic management protocols for hatchery management, restocking, translocations, conservation captive breeding programs, fish rescues and interventions and the monitoring of threatened species. Protocols for the collection, preservation and storage of genetic material (e.g. fin clips, biopsy material, scales, bones, cryopreserved sperm, etc.) were also identified.

Previous and contemporary genetic research of MDB species was reviewed to highlight and map inferred genetic boundaries within the Basin. All available published and unpublished molecular data were compiled to assist in determining genetic structuring, ecologically sustainable units and management units. Strengths, weaknesses and implications of these data were considered, knowledge gaps highlighted and methods for addressing these gaps were discussed.

A workshop was held to determine what level of genetic management is appropriate for fish in the MDB and bring together experts to present the latest thinking on defining conservation units, to help inform development of a framework for prioritising and managing evolutionary distinction. Review findings and workshop outputs were then used to inform development of guidelines for management of genetic diversity in Australian native fish within the MDB which includes:

  • a review of current genetic issues and management practices across the MDB;
  • a review of the genetic structuring for native fish and crustacean species in the MDB including knowledge gaps;
  • guidelines and recommendations for genetic management within the MDB;
  • a genetic management template for fish stocking; and,
  • recommendations from the Management of Genetic Resources for Fish and Crustaceans in the Murray-Darling Basin workshop.
Figure 1. Studies have indicated there may be up to five discrete populations of Golden Perch (Macquaria ambigua) in the Basin (Photo courtesy of Jamin Forbes)

Figure 1. Studies have indicated there may be up to five discrete populations of Golden Perch (Macquaria ambigua) in the Basin (Photo courtesy of Jamin Forbes)

Figure 2. Studies have shown there to be five distinct genetic populations of Murray cod in the Basin  (Photo courtesy of Jamin Forbes)

Figure 2. Studies have shown there to be five distinct genetic populations of Murray Cod in the Basin (Photo courtesy of Jamin Forbes)

Findings and recommendations: Available data on genetic subdivision for 65 fish and crustacean species across the MDB were reviewed and discussed in the context of management for these species. This review highlighted significant genetic differences between populations of native fish and crustaceans within the Basin. These genetically different populations potentially contain unique evolutionary heritage that will require specific approaches to manage.

A number of recommendations were provided from this project:

  • Populations that are defined as distinct genetic management units should be treated as unique populations with limited transfer of individuals between units (Figs 1 and 2).
  • Information provided through this project should be used to develop a unified approach to the management of genetic diversity within the MDB.
  • The substantial knowledge gaps for species with insufficient genetic data (outlined in species profiles) should be addressed to allow the identification of genetic management units for the MDB.
  • Adequate stocking and hatchery genetic protocols should be adhered to for all breeding programs within the MDB.

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.

Understanding the effects of environmental flow allocations on the lateral movements of native fish in the Barmah-Millewa Forest

Key words: Environmental flows, floodplain wetlands, fish migration, regulators, Native Fish Strategy. 

Passage to and from floodplain wetland areas is very important for native fish, as some species utilise these areas for spawning, feeding and recruitment (survival of fishes from eggs to reproductive stage). Regulators were originally installed in the Barmah-Millewa Forest (BMF) to keep water out during the agricultural irrigation season (Fig 1), however such regulators are now thought to adversely effect the lateral movements of native fish. 

Broad aim and methods. This project aimed to investigate the lateral movements of native fish during normal river discharges and during an environmental water allocation (EWA) in order to determine the impact of regulators on native fish movements in the BMF. 

Sampling was conducted within a number of key fish species in the BMF. Electrofishing was used to determine the presence and abundance of species within habitats sampled (Fig 2). Egg samples were taken from adult individuals to understand whether fish in regulated offstream habitats developed and spawned naturally. Tagging (radio-telemetry and t-bar tagging) was used to monitor movement behaviour, and drum, fyke, frog and larval nets were used to determine which species are using the waterways sampled and to investigate whether movement is influenced by flow. Water quality parameters were also recorded. 

Figure 1. Regulator on Gulpa Creek. (Photo courtesy Matthew Jones, ARI)

Figure 1. Regulator on Gulpa Creek. (Photo courtesy Matthew Jones, ARI)

Figure 2. Golden perch fitted with radio transmitter. (Photo courtesy Matthew Jones, ARI.)

Figure 2. Golden perch fitted with radio transmitter. (Photo courtesy Matthew Jones, ARI.)

 

Findings: Results suggest that movement between the Murray River and wetland creeks occurs on a regular basis in unregulated parts of the BMF. Fish generally respond to changes in flow by moving into these creeks on rising flows and returning on falling flows. 

In regulated systems, fish generally approached the regulator on falling flows, presumably trying to return to the Murray River like fish in unregulated creeks, but being prevented from returning by the regulators they therefore remained stranded downstream. Movements back to the Murray River were only possible for a few large-bodied individuals during flood conditions when regulators were drowned-out and water velocities and turbulence reduced to the extent that such fish could escape. 

Rising water levels associated with the EWA induced fish to move into unregulated wetland creeks and fish generally occupied these creeks for the duration of the EWA. Results indicated that fish remain in these creeks for as long as they are inundated to spawn and feed. Modelled data suggest that without the EWA, flows would have dipped below bankfull several times in late 2005, which, based on previous movements, would most likely have resulted in fish leaving wetland creeks, possibly interrupting feeding and/or spawning activities. 

Lessons learned and future directions: Results from this project will be used to guide the use of off-channel regulators to facilitate movement of native fish to and from off-channel habitats to promote spawning and reduce the likelihood of fish being stranded in drying off-river habitats. The results of this project will also provide information for better targeting of environmental water releases for native fish. 

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

Contacts: Dr Matthew Jones, Arthur Rylah Institute for Environmental Research (ARI). (03) 9450 8600, matthew.jones@depi.vic.gov.au

Link: http://www.mdba.gov.au/sites/default/files/pubs/MDBA-13067-Barmah-Millewa-Forestv2.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

Mesoscale movements of small and medium-sized fish in the Murray-Darling Basin

Key words: fish migration, mesoscale movement, Murray-Darling Basin, Native Fish Strategy

Understanding the scale and movement requirements of fishes is important for their sustainable management. Information is available on the larger scale movement of adults of larger species in the Murray-Darling Basin (MDB), however prior to this project little was known about the movement of smaller or rarer species or early life history stages of larger species.

Broad aim and specific objectives: This project aimed to investigate mesoscale movement (movement beyond a single river meander or pool riffle sequence, or the movement between the river channel and its floodplain) for MDB fish species and/or life history stages for which there is little existing information. This included an investigation into both longitudinal (up and down the river) and lateral (across the river and floodplain) movements and possible movement triggers.

Methods: Lab-based tag retention trials were conducted to test the efficacy of Visual Implant Elastomer (VIE) tags and Passive Integrated Transponder (PIT) tags in a range of native fish species prior to field application. Field-based sampling took place both during regular and flood conditions, using a combination of conventional tagging, radio-telemetry and standard electrofishing and fyke netting techniques to study the movement of a range of northern MDB fish species. A mark-recapture study was undertaken to determine the movements of known individual fish or (in the case of smaller species or life stages) known batches. Quantitative or semi-quantitative sampling of fish numbers took place at regular intervals over a range of habitats to follow movements of fish populations. Data on environmental parameters that may trigger fish movements were recorded both using data collected by other agencies and project data loggers. Radiotelemetry data of Bony Herring (Nematalosa erebi) and Spangled Perch (Leiopotherapon unicolor) were also used to provide additional information on movements.

Figure 1. Inserting a radio transmitter into a Bony Herring (Photo courtesy of Michael Hutchison)

Figure 1. Inserting a radio transmitter into a Bony Herring (Photo courtesy of Michael Hutchison)

Figure 2. Inserting a PIT tag into a juvenile Golden Perch (Photo courtesy of Michael Hutchison)

Figure 2. Inserting a PIT tag into a juvenile Golden Perch (Photo courtesy of Michael Hutchison)

Figure 3. A Rainbowfish with VIE tag, ready for release (Photo courtesy of Michael Hutchison)

Figure 3. A Rainbowfish with VIE tag, ready for release (Photo courtesy of Michael Hutchison)

Findings: During the study, type of flow (natural or artificial), moon phase and time of year were found to be associated with movements of fish species. Carp Gudgeons (Hypseleotris spp.), Bony Herring, Spangled Perch and Golden Perch (Macquaria ambigua) sub-adults and juveniles were more mobile on natural flows than on flow releases from dams. This indicates that migration of these species may be stimulated by odours in run-off from floodplains. On falling flows there was a tendency for downstream migration by Carp Gudgeons, Bony Herring, and Spangled Perch of all sizes, Golden Perch sub-adults and juveniles, Dwarf Flathead Gudgeon (Philypnodon macrostomus) and juvenile Hyrtl’s Tandan (Neosilurus hyrtlii). This may be to avoid desiccation. Only a small proportion of the Murray-Darling Rainbowfish (Melanotaenia fluviatilis) population appeared to move. Of those that did, most moved upstream. In contrast to other species, Murray-Darling Rainbowfish were most mobile during artificial flow releases. They may prefer clearer water for movements associated with courtship displays and breeding.

In most species of fish, adults had more of a tendency to move upstream and juveniles downstream. This trend was very strong in Hyrtl’s Tandan. Most native species displayed diminished movement behaviour during the winter period, corresponding to periods of lowest flow in the northern MDB. Peak movement occurred in spring for Carp Gudgeons, Spangled Perch, Hyrtl’s Tandan, Olive Perchlet (Ambassis agassizii) and Murray-Darling Rainbowfish. These movements are believed to be associated with their reproductive strategy as many fish collected at this time were reproductively ripe.

Peak movements of juvenile and sub-adult Golden Perch and Bony Herring occurred during autumn. In the northern MDB, such behaviour would be a useful adaptation to enable dispersal to refuges prior to the onset of the winter and early spring dry season.

Carp Gudgeon were recorded moving up to 13 km upstream and more than 5 km downstream. Evidence suggests that Spangled Perch, Bony Herring, Dwarf Flathead Gudgeon, juvenile and sub-adult Golden Perch also make upstream movements in excess of 10 km. Downstream movements up to 2 km were recorded for Spangled Perch and up to 5 km for Bony Herring. Downstream movements of hundreds of metres were recorded for juvenile and sub-adult Golden Perch and Hyrtl’s Tandan. 

Lessons learned and future directions: It is very important that managers consider the upstream and downstream movement of small fish when prioritising fish passage investment. In particular, the downstream movement for many species dictates that future fishway design should accommodate small-bodied fish as well as the premier native sport fish and other large-bodied species.

There is a need for improved coordination by fisheries managers and water managers on different methods of delivering water to increase lateral connectivity. The potential benefit of delivering water from dams less frequently or more strategically, and in larger volumes to replicate natural flows, needs to be understood by fisheries and water managers. Increased flow delivery may be achieved by combining environmental flow releases with natural flow events or irrigation releases.

Lateral habitats (e.g. lagoons) may be important for reproduction and long-term survival of some fish species and connectivity to and from the main channel should be an important consideration when determining flow releases. 

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/MDBA-Mesoscale-Movement.pdf