Category Archives: Fish

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

Posted on 29 January 2014 by | Comments Off on 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

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Pest animal issues & solutions

Assessing fishway options for weirs of the northern Murray-Darling Basin

Posted on 29 January 2014 by | Comments Off on Assessing fishway options for weirs of the northern Murray-Darling Basin

Key words: Fish passage, fish migration, fisway, prioritisations, northern Murray-Darling Basin

Threats and Impacts: Barriers to migration have been identified as a major contributor to the decline of native fish species within the Murray-Darling Basin. The Murray-Darling Basin Authority have made significant investment in improving fish passage along the Murray River and associated anabranches through the Lake Hume to the Sea program and the Living Murray Initiative. Despite the improvements along the Murray River, this investment has not been matched in the Northern Murray-Darling Basin. At present, the movement of fish within and between river systems north of Menindee Lakes remains significantly restricted by dams and weirs without adequate fish passage. 

Broad aim and methods: This project set out to develop concept designs and engineering costings for the highest priority weirs in the Northern Murray-Darling Basin.

A review of literature was undertaken initially to assess the likely composition and migratory requirements of the fish fauna in the Northern Basin. An analysis of available options for fish passage was undertaken, and justification provided for the preferred options in terms of the ecological, hydraulic and technical design constraints associated with each weir.

Assessment of structures within the northern Basin identified 12 priority sites within four sub-catchments. These structures were identified as priority sites due to their impact on migrating fish fauna, their potential benefit-cost ratio, and the river length that would be reinstated should the fish passage be provided at the site.

Of the 12 priority weir sites identified, five were investigated for feasibility of fishway installation and identification of fishway designs that would be directly applicable to five of the other sites plus generic types of weir (e.g. sheet pile with rock-fill face) in the northern Basin.

Of the two remaining sites, one has existing detailed design and cost estimates (Bourke Weir), while the second (Chinchilla Weir and gauge) requires further investigations – the costs of which were not possible within the budget for this project.

Fishway concept designs were developed at key representative sites which were specifically designed to suit the fish assemblage and semi-arid ecology of the northern Basin. Designs considered constructability, materials, regional context, maintenance and ownership, and allowed the development of cost estimates, with contingencies, to enable the financial and practical scope of the project to be assessed.

Figure 1 - Priority structures identified in the Northern Murray-Darling Basin

Figure 1 – Priority structures identified in the Northern Murray-Darling Basin

Figure 2 - Cunnamulla Weir, one of the priority sites identified for fish passage remediation in the northern basin. Photo courtesy of Scott Nichols

Figure 2 – Cunnamulla Weir, one of the priority sites identified for fish passage remediation in the northern basin. Photo courtesy of Scott Nichols

Findings: The river reaches where the weirs are located were noted to have high ecological value, with known native fish populations, high quality fish habitat, and long river reaches that would be reinstated for migration, either because of few nearby barriers or because of nearby weirs with fishways.

Spanning river systems in both NSW and Queensland, 12 high priority sites were identified, together with concept designs and investment costs to fix the top five barriers to fish passage. These weirs were chosen because of their anticipated high benefit/cost ratio.

The project identified that there are two feasible approaches to rehabilitating fish passage in the northern Basin:

  • provide fish passage at the top 11 priority structures to reinstate 2,086 km of river channel. The total cost was estimated at $14.56 m.
  • provide a strategic, holistic, program re-establishing broad-scale river connectivity of over 3,242 km. The total cost was estimated to be approximately $70 m.

The key features that make a fish passage program feasible in this area are:

  • the main-stem barriers are not numerous (42 for a broad-scale program reinstating over 3,200 km of river).
  • most of the barriers are low-level weirs between 1.5 m and 4.5 m high, with the exception of only eight structures.
  • most of the sites are relatively easy to work with.

Lessons learned and future directions: This project has provided a clear direction for strategic investment to deliver substantial improvements in fish passage connectivity, reducing fragmentation of fish populations in the northern Murray-Darling Basin. Fishway concepts were specifically designed to suit the fish assemblage and semi-arid ecology of the northern Basin and considered the feasibility of construction, materials, regional context, maintenance and ownership. 

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

Contact: Scott Nichols, Fisheries New South Wales, (02) 66261396, scott.nichols@industry.nsw.gov.au, 1243 Bruxner Highway, Wollongbar, NSW 2477

Link: http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0020/456203/Fishway-Options-for-Weirs-of-the-Northern-MDB-FINAL-for-web-Jan13.pdf

 

 

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Landscape pattern & design, Riparian & stream ecology, Techniques & methodology

Using hydroacoustics to monitor fish migration

Posted on 26 January 2014 by | Comments Off on Using hydroacoustics to monitor fish migration

Key words: split beam, hydroacoustics, sound waves, fish counting, fish migration.

Understanding how effective a new fishway is at providing passage for migratory fish is an important part of the design process. Most methods for sampling fish communities to understand movement rely on capture-based methods, which have issues with affecting fishes behaviour and thus biasing the results. Remote monitoring that is not based on capture removes such bias. Hydroacoustics (underwater sound waves) is one method of monitoring fish migration.

Project aim and methods: This project aimed to investigate a hydroacoustic method for counting fish migrating at the Murray River fishways. A 200 kHz split-beam hydroacoustic system was installed at the Lock 10 fishway in November 2007 to detect fish moving through the fishway exit channel. A dual-frequency identification sonar (DIDSON) acoustic system was also installed to provide video-quality images able to be used as a comparison with the split-beam acoustic data.

Figure 1: MD823 Fig 3 Echogram showing a fish (encircled in red) swimming out of the fishway exit channel at Lock 10 fishway (Photo courtesy of Andrew Berghuis)

Figure 1: MD823 Fig 3 Echogram showing a fish (encircled in red) swimming out of the fishway exit channel at Lock 10 fishway (Photo courtesy of Andrew Berghuis)

Figure 2: DIDSON laptop display. Photo courtesy of Lee Baumgartner

Figure 2: DIDSON laptop display. (Photo courtesy of Lee Baumgartner)

Figure 3 - Trial of acoustic and didson sounders set within fishway looking out at exit. (Photo courtesy of Mick Bettanin, Fisheries NSW.)

Figure 3 – Trial of acoustic and didson sounders set within fishway looking out at exit. (Photo courtesy of Mick Bettanin, Fisheries NSW.)

Findings:  The DIDSON system appeared to have several advantages over the split-beam system, but both were suggested to have merits for fish counting. The split-beam hydroacoustic system gave an automated fish count of up to 3.96 fish per minute moving through the fishway, but verification using the DIDSON indicated that nearly half of these fish were not detected. Data from the DIDSON system were also analysed, and an automatic fish count of up to 1.09 fish per minute was established. Visual verification over the same one-hour portion as the split-beam data found that over twenty five percent of fish recorded by the DIDSON system were not detected.

Automatic fish length detection consistently underestimated fish length, most likely due to the poor orientation of fish to the acoustic beams. However there did appear to be some relationship between acoustic target strength of fish detected with the split beam acoustic system and fish size, suggesting that this may require further investigation. The DIDSON appeared to provide fairly accurate fish measurement of fish and ongoing data collection and analysis may further improve estimates.

The project highlighted a major limitation of hydroacoustics, being an inability to discriminate between fish species, though it was noted that further experiments might assist in species recognition.

Low rates of fish migration and reduced river levels precluded the ongoing collection of data beyond the initial sampling period.

Lessons learned and future directions: The current study found that despite some limitations, use of hydroacoustics may assist in assessing migrating fish at man-made barriers, and assist in informing future fishway designs, which will have follow on benefits for the long term recovery.

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

Contact: Andrew Berghuis, Aquatic Biopassage Services, 0407 559 908, andrew@aquaticbiopassage.com.au.

Link: http://www.depi.vic.gov.au/__data/assets/pdf_file/0014/204251/ARI-Technical-Report-177-Performance-of-a-single-frequency-splitbeam-hydroacoustic-system.pdf

 

 

 

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Monitoring, Planning, monitoring & assessment, Riparian & stream ecology

Sea to Hume Fishways – lessons from monitoring

Posted on 26 January 2014 by | Comments Off on Sea to Hume Fishways – lessons from monitoring

Key words: Fish migration, fishways, monitoring, barriers, River Murray, Native Fish Strategy

Native fish species move along rivers for breeding, dispersal, to access habitat, escape threats and establish new territories. In 2001 the then Murray-Darling Basin Commission approved the construction of fishways (Figs 1 and 2) on all of the Locks and Barrages from Hume Dam to the mouth of the River Murray, thus ensuring continuous fish passage for 2,225 km. It was also vital to undertake monitoring at appropriate scales to determine whether constructed fishways were successfully restoring connectivity along the river for native fish species.

Project aims and methods: In order to assess whether the fishways were being effective, researchers sought to answer four questions:

  1. Are the fishways allowing passage of a full range of size classes and species of fish?
  2. Are the fishways reducing accumulations of fish downstream of the barrier?
  3. Are the fishways contributing to positive changes in the abundance and diversity of native fish in the river?
  4. Are the location, design and operation of the fishways optimised?

To answer these questions, two types of monitoring were performed – compliance monitoring to see if each fishway was working optimally and long-term monitoring to see if the fishway program was having a positive impact on native fish populations. 

Electrofishing and fishway trapping were used to sample fish communities and determine whether they were successfully ascending fishways. Sampled fish were identified and counted, and subsamples measured to enable species/size-specific trends to be identified. Environmental variables such as water temperature, river flow etc. were also recorded for analysis. 

Fig 1. Lock 3 Vertical Slot Fishway 3. (Photo Jarrod McPherson NSW DPI)

Fig 1. Lock 3 Vertical Slot Fishway 3. (Photo Jarrod McPherson NSW DPI)

Fig. 2. Lock 10, vertical slot fishway, assessment cage. (Photo Lee Baumgartner NSW DPI)

Fig. 2. Lock 10, vertical slot fishway, assessment cage. (Photo Lee Baumgartner NSW DPI)

Findings:

  • From sampling at Lock 8, the original aim for the passage of all fish, for each species, from a minimum of 31 mm long, all medium sized fish from 90 to 600 mm long, and adult Murray Cod (Macculochella peelii) to a maximum of 1000 mm long, was achieved.
  • Young-of-year (less than 1 year old) Bony Herring (Nematalosa erebi), and the juvenile size classes of Un-specked Hardyhead (Craterocephalus stercusmuscarum), Murray Rainbowfish (Melanotaenia fluviatilis) and Australian Smelt (Retropinna semonii) were unable to ascend the fishway.
  • several species smaller than the minimum target design size (40 mm), such as Carp Gudgeon (Hypseleotris spp.), Murray Rainbowfish and Unspecked Hardyhead, previously thought not to be migratory were, in their thousands, unsuccessfully attempting to gain upstream passage through the fishways.
  • Small-bodied fishes numerically dominated the total catch at the Lock 8 fishway and during spring and summer the bulk of these were juveniles and young-of-year. This highlights a need for an additional fishway design criterion that includes seasonal changes in fish sizes and migratory biomass, rather than simply aiming to pass a minimum length criterion alone.
  • At Lock 8 few non-native fish species were captured in the fishway, with the exception of adult Carp (Cyprinus carpio), which had an 87% success rate of negotiating the fishway.
  • Although the new vertical slot fishways at Locks 7, 9 and 10 performed to design specifications, there were species-specific variations in the minimum size of successfully ascending fish. In particular, many smaller Bony Herring and Golden Perch (Macquaria ambigua) could not negotiate the fishways.
  • At fishways constructed at the Barrages at the mouth of the Murray, over 98% of fish collected were small-bodied species which were attempting to use the fishways but were unsuccessful due to the design hydraulics, particularly at the vertical-slot fishways. Nevertheless, some small-bodied species were observed using the fishways during periods of low flow between the Lower Lakes and Coorong.
  • Large-bodied estuarine species such as Black Bream (Acanthopagrus butcherii), Mulloway (Argyrosomus japonicas) and various species of Mullet were noticeably absent from the fishways but were present in the vicinity of the Barrages. A large-scale acoustic tracking program was initiated to determine fish passage success for these species.

Longer term monitoring (at Locks 1-3) showed that:

  • Catches were dominated mostly by small and medium bodied species during low flow conditions. Murray Cod were rarely encountered but the captured population was dominated by large individuals, suggesting that recruitment (survival of fishes from eggs to reproductive stage) opportunities for this species in the lower reaches of the River may be limited.
  • Surveys consistently showed large downstream aggregations of fish, dominated by small-bodied native fish and Carp.
  • Australian Smelt, Bony Herring, Flat-headed Gudgeon (Philypnodon grandiceps), Unspecked Hardyhead, Murray Rainbowfish and Carp Gudgeon remain common in the main channel of the lower River Murray.
  • Differences were observed in the diel (daytime vs night-time) composition of the fish community. Some species and sizes were moving exclusively at night.

Lessons learned and future directions:  While many overseas fishways are designed to pass only a few large-bodied economically important fish species, the Murray River fishways are able to restore passage for the majority of migratory species.

The attempted upstream movement of small-bodied threatened species such as Carp Gudgeons, Murray Rainbowfish and Unspecked Hardyhead was not known before the ‘Sea to Hume’ program, highlighting the need to identify the migratory community prior to fishway construction. The subsequent passage of Carp Gudgeons through modified fishways will assist in restoring the ecological processes of dispersal and recolonisation for this species.

At the Barrages, fishway types identified as being suitable to facilitate small-bodied fish passage include small fish locks (mechanical elevator-style fishways), low-head vertical-slot fishways (which use a sequence of pools and baffles to control water depth and velocity) and rock-ramp fishways (which are more natural looking fishway designs constructed of rock in such a way as to create a sequence of pools separated by rocky ridges to control flow). To be effective and efficient at facilitating the passage of small-bodied fish over a long migration season (potentially August to March) these fishways will need to operate over a broad range of flow and headloss conditions. Securing environmental water allocations and delivering these in a manner that resembles natural seasonal cycles will potentially deliver the greatest ecological benefit.

Observed changes in diel abundance patterns of fish assemblages in the lower Murray River

has important implications for future fish passage studies: both day and night samples are required to adequately describe the migratory community.

Remote passive integrated transponder (PIT) tag reader systems, which have been installed at most of the new fishways, continually monitor for any of the 30,000 fish PIT tagged in the Murray River. Upon completion of the program a tagged fish can now be tracked up and down the River for its whole lifetime, providing important ecological data and also offering community stakeholders the opportunity to be involved in the program.

Restoring fish migration in over 2000 km of river is likely to have flow-on benefits. These will maximise the potential success of other management practices such as habitat restoration and threatened species protection for the rehabilitation of native fish populations in the Murray-Darling Basin.

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

Contacts: Dr Lee Baumgartner, Fisheries NSW, + 61 2 6958 8215, lee.baumgartner@dpi.nsw.gov.au,

 Link: http://www.mdba.gov.au/sites/default/files/archived/mdbc-NFS-reports/2179_Sea_to_Hume_Dam_final_report.pdf

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Monitoring, Planning, monitoring & assessment, Riparian & stream ecology, Standards

Evaluating use of chemical marking in monitoring stocked fish

Posted on 26 January 2014 by | Comments Off on 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.

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Posted in Fish, Freshwater aquatic, Planning, monitoring & assessment, Riparian & stream ecology

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

Posted on 26 January 2014 by | Comments Off on 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

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Integrating ecosystems & industries, Planning, monitoring & assessment, Riparian & stream ecology

Counting Murray-Darling fishes by validating sounds associated with spawning

Posted on 26 January 2014 by | Comments Off on 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

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Planning, monitoring & assessment, Techniques & methodology

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

Posted on 26 January 2014 by | Comments Off on 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

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Posted in Fauna & habitat, Fish, Planning, monitoring & assessment, Riparian & stream ecology

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

Posted on 26 January 2014 by | Comments Off on 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

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Posted in Fauna & habitat, Fish, Planning, monitoring & assessment, Pollution issues & solutions, Riparian & stream ecology

Management of genetic resources within the Murray-Darling Basin

Posted on 26 January 2014 by | Comments Off on 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.

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Posted in Fauna & habitat, Fish, Freshwater aquatic, Genetic issues, Riparian & stream ecology