Giant Freshwater Crayfish Recovery Project - newsletter issue 3 June 2022

ISSUE 3 | JUNE 2022

Giant Freshwater Crayfish Recovery Project

Welcome to the third newsletter about the Giant Freshwater Crayfish Recovery Project being undertaken by the Cradle Coast Authority’s Natural Resource Management team, Cradle Coast NRM

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This project is supported by Cradle Coast Authority, through funding from the Australian Government.

Which crayfish do you have??

Tasmania has a high diversity of crayfish fauna with 33 named native crayfish in 5 genera in Tasmania plus Cherax, making 34 in all. Many of these species are listed as vulnerable or threatened under both Tasmanian and Federal legislation. Cradle Coast Authority (CCA), with support from the Australian Government, is currently running a project with agricultural landholders to protect and improve habitat for the Giant Freshwater Crayfish (Astacopsis gouldi) in six priority catchment areas.

Astacopsis is a genus of crayfish endemic to Tasmania. There are three species of Astacopsis: Astacopsis gouldi, Astacopsis franklinii and Astacopsis tricornis. A.franklinii is found in the eastern half of the state and A. tricornis in the western part of the state.

The Giant Freshwater Crayfish (Astacopsis gouldi) is the largest freshwater crustacean in the world and is unique to northern Tasmania. It can grow up to 6 kg and up to a metre in length. Its colour can vary from dark brown-green to black or blue. The Giant Freshwater Crayfish can be distinguished from any other Tasmanian crayfish by the ridge running down the middle of the rostrum (the pointed structure between the eyes). Sometimes they may have different sized claws if they are regenerating after having been in a fight. They are very slow-growing and long-lived, with females taking up to fourteen years before they can breed and males up to nine years. They can live up to sixty years. They live mainly in flowing or still waters, in logs or along undercut banks, although they are shy and secretive animals.

Adult Giant Freshwater Crayfish often show signs of injury from fighting, such as the missing claw on this male.

In contrast, the species of Engaeus, Geocharax, Ombrastacoides and Spinastacoides are small freshwater crayfish with a body length of under 10 cm.

Within the genus Engaeus there are approximately 15 known species, 13 of which only occur in Tasmania. Most species of Engaeus are characterised by their ability to burrow. The burrowing crayfish live their entire life within their burrow systems in muddy banks, seepages and peaty areas. Burrows can be simple and shallow or complex and extensive. The distinctive chimneys at the entrances to the burrows are all that most of us will ever see of a burrowing crayfish.

Chimney of a burrowing crayfish.

The Tasmanian Engaeus species are also mainly found in the north and west of the state. Some of the species are quite widespread, like E. fossor, but most have restricted ranges. The Burnie Burrowing Crayfish (E. yabbimunna), and the Central North Burrowing Crayfish (E. granulatus) are EPBC-listed threatened species. Burrowing crayfish have a narrow body and claws that open vertically rather than horizontally to the body, allowing for larger claws in the confined space of narrow tunnels.

Both the burrowing crayfish and the Giant Freshwater Crayfish eat decaying organic matter such as rotting leaves, twigs and wood but will supplement their diet with invertebrates like worms and grubs. Threats to all crayfish include damage to streambanks from stock and machinery; land clearing and loss of vegetation and shading; runoff and pollution entering the waterways; sedimentation from erosion and runoff; introduced species such as mainland yabbies that might introduce disease or prey on native crayfish; and climate change which might result in increased flood events and bushfires.

The NatureTrackers project, Claws on the Line aims to monitor the threatened Central North Burrowing Crayfish and its relatives. You can record your observations of crayfish chimneys in iNaturalist or get in touch with the NatureTrackers or CCA NRM team for more information.

2.

Update on the Giant Freshwater Crayfish Recovery Project As we enter the final 12 months of the Giant Freshwater Crayfish Recovery Project, landholders are very busy implementing their onground project works. The project started in October 2019 and continues to June 2023. It is working with agricultural landholders in targeted sections of rivers in the Cradle Coast area. The aim of the project is to protect known populations of Giant Freshwater Crayfish and improve the extent and quality of their habitat.

We have now been working with agricultural landholders in the following six priority areas to develop projects: Upper Leven River Part of the Flowerdale River and tributaries in the Lapoinya area Black River Good off stream watering points on a solid gravel base provide good quality water for stock; reduce sedimentation into waterways; and the gravel base reduces erosion from stock trampling around the trough.

Hook Creek and Detention River Roger River, Spinks Creek, Upper Duck River Lower Inglis River

To date, 22 landholders have entered into funding agreements to protect or rehabilitate 47 km of river corridors. With funding from the Australian Government, the aim of the project is to rehabilitate at least 24 km of river bank, in the priority areas, which results in both sides of the stream being restored or having improved condition.

We have had good levels of interest from adjoining landholders, enabling us to ensure long reaches of river are protected.

In some instances, landholders have already fenced the river to exclude stock using previous funding programs or from their own resources, but have undertaken weed control and/or revegetation under this funding program. Other landholders have used this funding opportunity to put a conservation covenant over good remnant vegetation on their properties, including along their riparian corridor.

The kind of works being funded include: Riparian fencing to exclude stock and install offstream water points.

Native vegetation establishment and weed control to provide timber recruitment into and along the waterway.

Erosion control works to stabilise banks or beds of waterways.

Establishment and management of filter zones or buffer strips through fencing and re-vegetation.

Site monitoring.

Establish conservation covenants and manage areas of good remnant native vegetation for conservation.

The focus of the project for the final twelve months will be working with individual landholders to implement the on-ground works or conservation programs identified in their funding agreements.

Adequate widths or “buffers” between the top of the high bank and the riparian fence are essential to ensure vegetation can become established and hold the bank together in flood events, as well as providing a filter strip for sediment and nutrients flowing from the adjoining paddocks to the waterway.

3.

The important role vegetation plays in waterway stability and habitat The land alongside your waterways is probably your property’s most productive, thanks to its deeper soils and higher moisture content, but it is also the most vulnerable to damage from stock impacts and flooding.

Tree roots hold together an eroding outside bend. Eventually a stable 3:1 batter slope will form, with revegetation undertaken behind the batter.

Riparian areas are easily damaged by stock that eat and trample the vegetation, destroy soil structure and release effluent in and around the waterway. Without vegetation on the batters of the waterway and on top of the high bank, the riparian land is susceptible to bank erosion and slumping in times of high flow or flooding.

A good mixture of native vegetation – trees, shrubs and groundcover - is essential to provide stability to the waterway banks as well as providing habitat for the animals (large and very small) that rely on our waterways too. Diverse riparian vegetation with density and structure can slow the flow of the water and armour the banks.

Riparian vegetation also helps filter out the nutrients and sediment contained in runoff, which reduces pollution of the waterway leading to excess algae growth and water weeds. In addition to providing a shading effect on the waterway, riparian vegetation can also provide shade and shelter for paddocks adjoining the waterway.

Good riparian vegetation has a variety of species and includes groundcover, shrub layers and trees. Deep rooting trees on the top of the high bank provide bank strength and stability. Isolated large trees or scattered clumps of shrubs will not provide the same shelter and bank strengthening ability as a healthy and dense stand of vegetation. Natural regeneration may occur once stock and grazing are excluded from the waterway but in some instances, revegetation or replanting of particular species may be required too.

For example, mature trees may be present but no shrub layer, so infill planting may be recommended, particularly if seed stocks have disappeared as a result of previous management.

Isolated trees or sparse vegetation does not adequately protect the banks and batters of the creek from erosion.

4.

Good riparian vegetation has a number of layers and goes from the edge and across a buffer area on the high bank.

Excluding stock is a great first step in protecting your riparian area, but you cannot “lock it up and leave it”. Just like other productive areas of your property the riparian land needs ongoing management. Weed issues are probably the most common ongoing management issue, as well as things like pest animals, stabilising erosion areas, or slowing the flow of water.

It is essential to keep on top of the weeds as soon as they emerge so that they don’t out-compete your plantings or your natural regeneration. The first two or three years after fencing are probably the most critical, after which your native vegetation should be able to out-compete the weeds. The banks of your waterways will be most vulnerable to weed invasion if they are bare or have been disturbed, for example from crossing construction or old stock tracks.

Revegetating the site after you have carried out weed control will reduce the risk of re-invasion. Managing weeds is also more effective when done on a sub-catchment scale or working with adjoining upstream and downstream neighbours.

The Giant Freshwater Crayfish Project is working with adjoining neighbours in sub-catchments to try and ensure a coordinated response.

Habitat requirements for Giant Freshwater Crayfish vary depending on their age. Young crayfish prefer shallow, fastflowing streams with bed materials such as cobbles and boulders that they use for shelter. Adults often move to slowerflowing reaches where they like undercut banks or logs and boulders to seek shelter under. They prefer well-vegetated streams with clear water and even, cool temperatures. In addition to providing shelter, in-stream logs and dead wood are critical for providing food. Vegetation along both banks of the waterway moderates temperature extremes and filters sediments from soil and effluent which would otherwise muddy the water and degrade crayfish habitat. Without a ‘messy’ layer of fallen leaves, logs, stones, and branches, the Giant Freshwater Crayfish will be without an environment to live and breed in.

Fencing your waterway or riparian area to exclude stock means that you will need to provide off-stream watering systems and off-stream shade. Troughed water is cleaner, more palatable to stock and easier for stock to access. Cleaner water encourages higher consumption of dry matter.

Finally, improved riparian management provides public as well as private benefits, and can impact landholders and water users both upstream and downstream of the area improved.

5.

The importance of baseline and ongoing monitoring?

Baseline monitoring was undertaken in all six priority areas before any project works were implemented. This, combined with monitoring undertaken at the end of the project in 2023, will help identify any changes or improvements that may have occurred in this stretch of river over the life of the project. Many of the proposed project works, such as revegetation, will take many years to get established and should provide longer term benefits such as re-introduction of timber into the river and moderating the impacts of heat waves. This will require longer term monitoring beyond the life of the project.

As part of the baseline monitoring, both juvenile and adult crayfish were captured in the priority areas, with the larger specimens tagged. Future monitoring will involve trying to use in-stream microchip readers to monitor the movement of these tagged adults or to recapture tagged animals and measure growth rates over time. The AUSRIVAS sampling that was also undertaken as part of the baseline monitoring uses aquatic macroinvertebrates (animals without backbones that can be seen with the naked eye such as mayfly, caddis fly, dragonfly larvae and shrimps) as biological indicators of river health. AUSRIVAS will also provide the means to measure changes in water quality over time.

For landholders who are interested in getting involved in citizen science projects relating to macroinvertebrate sampling, John Gooderham of the Waterbug Company (www.thewaterbug.net) helps to organise annual water bug surveys. Contact John directly or through your local Landcare group.

Above: Adult male crayfish trapped in October 2020, tagged and released.

Left: Same male trapped again in 2022. He had moulted and grown an additional 11 mm and was 300 g heavier than in 2020.

Photo credit: Todd Walsh Far left: Todd Walsh checking for a tag in an adult crayfish.

Circular Head Field Day and school presentation A Field Day was held in March 2022 on one of our project sites in the Detention River catchment, for students who are undertaking a TAFE course in Conservation and Ecosystem Management.

Students got to look at the riparian vegetation zone and hear from the landholder about the positive impact fencing has had on native vegetation regeneration along the corridor.

Todd Walsh provided a practical demonstration on the habitat and lifestyle requirements of the Giant Freshwater Crayfish and Fiona Marshall provided detail on the project.

Later in the day, a similar presentation was provided to Smithton High School senior students in the classroom, given there are a number of project priority areas in the Circular Head catchment area.

6.

TAFE students, CCA staff, Todd Walsh and the landholder discussing riparian vegetation and crayfish requirements at the Field Day.

Conservation covenants for Giant Freshwater Crayfish habitat Under the project, landholders in the priority areas may be eligible to develop a proposal for a conservation covenant to protect good quality Giant Freshwater Crayfish habitat, including surrounding native vegetation.

Some landholders have used this funding opportunity to develop proposals for conservation covenants on land with high quality GFC habitat and remnant vegetation on their properties, including riparian, floodplain and hillside forests.

Four separate conservation covenants have been approved in 2021-22 under the project to protect 74 ha of land surrounding nearly 5 km of high-quality Giant Freshwater Crayfish habitat in the Detention, Inglis and Leven River catchments.

An exciting benefit of these covenants has been the inclusion of 47.5 ha of Eucalyptus viminalis (White Gum) wet forest, listed nationally as “Critically Endangered”. The covenants also protect habitat for a range of other threatened and nonthreatened fauna and flora like Tasmanian Devil, Spotted-tailed Quoll and the Tasmanian Masked Owl, to name a few.

The four covenants will become part of the National Reserve Estate and will be protected in perpetuity, a great conservation outcome for Giant Freshwater Crayfish and other important natural values in north-west Tasmania.

Photo credit: Helen Morgan

What is a conservation covenant?

A conservation covenant is a voluntary agreement between the landholder and the Minister administering the Tasmanian Nature Conservation Act 2002. Conservation covenants aim to protect and enhance the natural, cultural and/or scientific values of the area of land under covenant. The covenant is placed on the land title, to provide long term protection to the area even if ownership changes.

Conservation covenants are part of Australia’s National Reserve System and provide the highest level of protection for private land conservation. Tasmania has over 900 conservation covenants protecting approximately 112,000 ha. Each covenant is tailored to suit the property and is developed with the landowners based on a natural values assessment and the management requirements. Conservation covenants provide landholders an opportunity to protect valuable Giant Freshwater Crayfish habitat on their land into the future.

Those who enter into a covenant under the Giant Freshwater Crayfish Recovery project can also access funding for any project works needed, as well as access stewardship payments up until June 2023.

7.

Photo credit: Todd Walsh

Poaching of the Giant Freshwater Crayfish Poaching of crayfish, particularly larger breeding adults, can lead to the loss of localised populations.

Under Inland Fisheries legislation, poaching of the Giant Freshwater Crayfish is illegal and can attract fines of up to $10,000 and up to $105,000 and/or a year in prison under Tasmanian Threatened Species legislation.

In addition, the taking of any crayfish (including the other two species of Astacopsis) is prohibited under Inland Fisheries legislation.

It is also illegal to take yabbies (Cherax destructor, an introduced species in Tasmania).

Members of the public and landholders are encouraged to report evidence of poaching of Giant Freshwater Crayfish via email to the Inland Fisheries Service at infish@ifs.tas.gov.au or call 0438 338 530 or Crime Stoppers on 1800 333 000.

When poaching sites are identified, Inland Fisheries can then monitor sites or install camera monitoring points.

Under the CCA project we are developing a poster about the Giant Freshwater Crayfish and how it is illegal to fish for this and other freshwater crayfish in Tasmania, which will be distributed widely through retail stores and tourism areas.

Further information: A short video on the Giant Freshwater Crayfish has been produced and is available on our website: https://www.cradlecoast.com/cca/natural-resource-management The Giant Freshwater Recovery Project is funded by the Australian Government and is due for completion in June 2023.

Get in touch For more infomation and to get involved in the project:

__________________________ Fiona Marshall Agriculture Project Coordinator Phone: 03 6433 8433 Mobile: 0413 382 390 Email: fmarshall@cradlecoast.com

Website: www.cradlecoast.com