Victorian Implementation Report 2004–2005

Driving Action 4: Controlling Alien Species

Highlights

Carp screens and a regional Carp management plan – a useful example from a southern Victorian catchment

The known distribution (red) of Carp in the Glenelg River catchment. Red dots indicate low numbers of Carp. The yellow lines indicate water transfer infrastructure into the Wimmera River catchment

Map: Ivor Stuart and Matthew Jones, DSE ARI

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Although the Glenelg catchment lies south of the Dividing Range in Victoria, it is linked to the Wimmera in the Murray-Darling Basin, through provisions for inter-Basin transfers of water. The Glenelg Hopkins CMA’s work on Carp is included in this report as an example of a catchment management authority that has successfully developed a Carp management plan, and a region that is actively pursuing their pest fish problems with new technologies.

In February 2001, Common carp were found in the Glenelg River catchment. Until then, the Glenelg River was one of the last Carp-free large rivers in south-eastern Australia. Surveys indicated that large numbers of Carp were present in Rocklands Reservoir, which links to the Wimmera. Three Carp were also recorded below the dam wall and one Carp was caught in the river downstream at the 5-mile outlet. Within a few days of the discovery of Carp below Rocklands Reservoir, 12 mm mesh screens were installed on the outlets from the reservoir to the river. On advice from the Arthur Rylah Institute (DSE ARI), additional 2 mm screens were installed prior to the 2002–2003 environmental flow release period and have been in place ever since to prevent transport of Carp eggs, larvae and juveniles. Subsequent surveys by DPI Fisheries Victoria did not record any Carp in the Glenelg River below Rocklands Reservoir for the next three years. However, in February 2004 a total of 16 juvenile Carp were caught once again at the 5-mile outlet, although no further Carp were collected in February 2005. Meanwhile, catch-a-Carp competitions within the reservoir caught 600 kg of Carp in 2003 and 1.2 tonnes in 2004.

Screens installed at Rocklands Reservoir to reduce spread of carp

Photo: MelodyJane, Glenelg-Hopkins CMA

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To manage this pest fish outbreak, a Technical Group was formed in 2001, comprising representation from the Glenelg Hopkins CMA (lead agency), DPI Fisheries Victoria, DSE Biodiversity and Natural Resources, local angling clubs and community groups, DSE Water Sector Group and Wimmera Mallee Water. DPI Fisheries Victoria surveyed the Glenelg over the past three years and Wimmera Mallee Water managed Carp screens installed at the outlets from Rocklands Reservoir. DSE ARI undertook a review of the Carp issue in the Glenelg River in 2002 to provide a framework for strategic assessment. Tasks included the collation of information on the present distribution of Carp, identification of possible sources of Carp infestation, identification of the potential for spread and reporting on potential impacts. In addition, identification of priority areas for future management, control options and evaluation of their likely success were considered. From this, the Technical Group developed a Carp management plan for the region (Glenelg Hopkins CMA 2003). This Plan has been implemented for the past two years with a combination of investigation, community education, monitoring and on-ground works.

Dead Carp

Photo: Janet Pritchard, DSE ARI

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Following the release of the regional Carp plan, a Carp management workshop was held in June 2004 in order to establish realistic targets for Carp management in the Glenelg River and to determine which actions were most likely to achieve these targets. As of 2004–2005, construction of new Carp screen designs is soon to commence construction. The existing screening arrangement that has been in place for over four years is far from ideal and is very high maintenance. Screens are vertical and tend to become blocked with filamentous algae dislodged from the channel walls, often forming an impenetrable mat on the screens. Wimmera Mallee Water often have to clean screens in excess of five times per day, and they run the risk of ‘blow-out’ due to the pressure build up behind them. On occasions the 2 mm screens have proven too problematic and have had to be removed to allow environmental flows to pass through. Where this has occurred, larval surveys have been undertaken to monitor the release water and the reservoir near the wall for signs of Carp eggs, larvae or juveniles.

New Carp screens should help remedy these difficulties and have been designed to retain Carp within Rocklands Reservoir, whilst still permitting environmental water entitlements to pass into the Glenelg River unimpeded. Innovative technology allows large volumes of water to be screened down to a very small size whilst the new screens also have the advantage of being relatively self-cleaning.

Prestigious awards for Williams Carp-separation cage

Some of the team involved in the development of the Williams Carp Separation Cage. (From left: Alan Williams, Ivor Stuart, John McKenzie, Matthew Jones, and John Koehn)

Photo: DSE ARI

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The innovative Carp-cage project for removing migrating Carp as they negotiate fishways has been recognised with two major awards: the Land & Water Australia Eureka Prize for Water Research in August 2004, and the David Ashton Biodiversity Award in March 2004.

The observation by Alan Williams, Goulburn Murray Water, that Carp jump as they passed through the Torrumbarry vertical-slot fishway has been turned into a novel method to remove this noxious fish species without harming or impeding native fish passage. A team at the Arthur Rylah Institute (DSE ARI), funded by the MDBC, has developed the ‘Williams Carp Separation Cage’, which is placed at the top of the fishway with a barrier across it. Carp tackle the barrier by leaping over it into a confinement area, whereas native fish move underneath and exit the fishway successfully. Testing of the cage at Torrumbarry Weir during 2003–2004 yielded a 90 per cent efficiency at removing Carp with virtually no native fish by-catch.

In 2004–2005 further testing and design improvements have been undertaken at Torrumbarry Weir, and the cage is now fully automated and remains highly successful in separating about 90 per cent of Carp from native fish. The native fish release system is working well and there have been no instances of native fish becoming caught in the Carp area. After this testing phase, the design for the cage has now been finalised, and meetings are underway to discuss the installation of Williams Cages on the new fishways at Locks 7, 8, 9, 10 and 15 in the near future.

Testing of design modifications to the Williams Carp Separation Cage

Photo: Ivor Stuart, DSE ARI

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A major Carp separating facility is also being considered by MDBC for Lock 1 in SA where the biomass of Carp is very large. A second phase of the project will be to test the cage below Lock 1 (without a fishway) to investigate whether Carp can be separated and collected within the river itself.

Oriental weatherloach

The Oriental weatherloach is classified as a noxious fish species in three Australian States. It has established self-sustaining wild populations and is spreading in many locations. Unfortunately, little research has been conducted in Australia on the biology of the weatherloach and ecological interactions with native invertebrates and fish species. This is now being addressed through a PhD at the University of Melbourne (2004–2007) investigating the impacts of Oriental weatherloach in Murray-Darling and Melbourne waterways. The study aims to identify which weatherloach species currently inhabit Australian waterways, and their distribution and abundance. In particular, molecular techniques are being used to study genetic variation and migration between populations to help predict impacts on aquatic ecosystems. Assistance is now being sought to gather samples of weatherloach from as many waterways as possible. If you can help collect weatherloach, please contact J.Kearns@pgrad.unimelb.edu.au.

Weatherloach

Photos: Joanne Kearns, UMELB

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Weatherloach

Photos: Joanne Kearns, UMELB

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