Ripples

Newsletter of the AUSTRALIAN PLATYPUS CONSERVANCY

ISSUE 42  - March 2010

REDUCING PLATYPUS DEATHS IN YABBY TRAPS

Ripples no. 41 highlighted the fact that illegal netting for fish, crays or yabbies has been responsible for more than half of all platypus mortalities reported to the APC where the cause of death can be reliably identified.  Since 2000, the most frequent source of net-related mortality has been enclosed yabby and cray traps, especially “opera house” traps.

According to industry sources, around 100,000 opera house traps are sold in Australia each year.  Although some restrictions on their use apply in most states and territories, many traps continue to be set illegally, often by persons who are both ignorant of fishing regulations and unaware of the risk that these traps pose to platypus and other aquatic wildlife.

The Conservancy is now working with platypus expert Dr Tom Grant (based in New South Wales) and the Wildlife Preservation Society of Queensland (WPSQ) to heighten community awareness of the fact that opera house traps continue to drown platypus throughout the species’ range.  Where necessary, changes to legislation are also being proposed to reduce the likelihood that non-target species die in the traps.      

A key part of this campaign involves asking wholesale and retail suppliers to become  involved in educating consumers about possible pitfalls and proper procedures to follow when using opera house traps. Leading retail chain Ray’s Outdoors is the first major business to support this initiative.  Opera house traps sold by this company are going to carry a tag with the unequivocal message: Opera house nets kill platypus, water-rats and turtles.  Check fishing regulations before using.  A special notice will also be displayed at the point of sale describing current state restrictions on the use of opera house traps.  

Such notices may usefully serve both to alert Australians to the dangers of enclosed yabby traps and also encourage the use of wildlife-friendly alternatives, such as simple baited lines or lift-style hoop nets.  Accordingly, we hope that those who care about platypus  conservation will consider directing their purchases of outdoor recreational equipment to retailers, like Ray’s Outdoors, who take steps to protect vulnerable freshwater species.

Although platypus do not regularly occur in the wild on the South Australian mainland, yabby nets are responsible for killing water-rats there.  Recent publicity associated with the APC’s Water-rat Report program has brought to light a spate of incidents where this attractive native mammal has drowned in enclosed yabby traps.  Accordingly, a joint submission has recently been sent to South Australia Fisheries, asking that legislation governing use of opera house nets be reviewed and potentially amended as per tighter regulations in nearby states.

In Queensland, where only minimal restrictions on the use of opera house traps currently apply, WPSQ is continuing to push for the rules to be changed to reduce the associated risk to wildlife.    

Meanwhile, the 2009/10 Victorian Recreational Fishing Guide includes for the first time an illustrated full colour page which spells out in bold headlines that it is illegal to deploy opera house traps in public waters such as creeks, rivers, lakes and reservoirs.  The text also explains that these traps threaten aquatic animals and hefty penalties apply when nets are set illegally.  Hopefully, this forthright approach will both encourage everyone to respect the rules and make it harder for anyone who chooses to flout the law to plead ignorance of current regulations.      

A METHOD TO COUNT ON

Visually-based survey methods have been used for years to track bird numbers for scientific studies or conservation monitoring.

Similarly, visual surveys are widely accepted to be a useful technique for monitoring kangaroo numbers, wherever the animals can be readily seen.

It should therefore not be surprising that visually-based methods are proving to be a powerful tool for monitoring platypus, particularly in the case of rivers or on-stream dams where substantial expanses of open water can readily be viewed from the banks.

For example, the graph below summarises how the frequency of community-based platypus sightings varied along the middle reaches of the Yarra River in three different parts of Melbourne (View Bank, Templestowe, and Eltham-Warrandyte) from the autumn of 2008 through the winter of 2009.

Summarising platypus sightings by quarter is probably the ideal way to get a feel for how populations are faring over periods of more than a year – allowing for natural seasonal variation while not getting bogged down in too much detail.

As you can see, quite an orderly (and similar) pattern was recorded over time in each of the three areas, with platypus seen most frequently from June to August and least frequently from March to May.  The relative number of sightings in different areas also remained remarkably constant over time, with consistently more animals seen in the Yarra at Templestowe as compared to Eltham and Warrandyte, where in turn consistently more platypus were observed in the river as compared to View Bank.

Intuitively, it makes sense that fewer platypus are seen at View Bank than the other locations, given that View Bank is located a few kilometres farther downstream, not far from the lowest limit of where platypus breed along the Yarra.

The large number of sightings at Templestowe presumably reflects the fact that the quality of platypus habitat is relatively good in this part of the river.  It is also possible that some popular platypus viewing spots in the Templestowe area (such as the Odyssey House swing bridge) coincide with locations where the animals tend to be particularly active and visible.

In exactly the same way, the results of platypus live-trapping surveys are sensitive both to the number of animals residing in an area and physical factors (such as water depth and channel profile) which determine how efficiently nets can be set.

No strong or consistent upward or downward trend is apparent when the frequency of platypus sightings in a given season in 2008 is compared with the corresponding frequency in 2009.  For example, sightings increased moderately from the winter of 2008 to the winter of 2009 at Templestowe and View Bank while declining moderately at Eltham and Warrandyte.  Given that numerous factors may potentially affect platypus activity at any given spot, these findings suggest that the number of animals occupying the middle reaches of the Yarra remained reasonably stable over the survey period.

Did You Know That...

Recent studies have documented a fourfold decline since 2000 in the number of platypus infected in Tasmania with the potentially life-threatening fungal disease mucormycosis.  Fortunately, no cases of the disease have emerged to date on the Australian mainland.

MURRAY RIVER PLATYPUS COUNT

The Australian Platypus Conservancy believes that monitoring platypus numbers should be a standard element in all new developments which potentially affect the species or its environment. 

In this context, the Conservancy is pleased that Norske Skog Paper Mill, a major producer of recycled paper in Australia, has decided to commission a study of the Murray River’s platypus population at Albury to provide information to help monitor its new wastewater disposal strategy.

The amount of salt that will be discharged to the river is predicted to result in only a small percentage increase in water salinity in the Albury area – to a level which should be well below what is known to be tolerated by platypus populations.

Nevertheless, the proposed research is a sensible and responsible precaution, which will complement other studies commissioned by Norske Skog to monitor water quality and river invertebrates (the platypus’s main food supply).  If any platypus-related problems linked to the discharge should arise, Norske Skog is committed to addressing the issue through remedial action. 

The forthcoming Albury platypus study will incorporate the Conservancy’s Platypus Count model of community-based visual monitoring, together with regular seasonal surveys carried out by APC staff.

Although the Murray River is one of Australia’s most important rivers, no systematic platypus studies have ever to the best of our knowledge been undertaken previously in the Albury-Wodonga region.  Accordingly, the monitoring program will provide baseline information needed to assess the effects of a range of potential threats to the species: reduced flows, degraded habitat quality, carp infestation, litter, and illegal use of fishing nets and yabby traps.

The Conservancy is also working in co-operation with the Upper Murray Landcare Network to develop an overview of the status and distribution of platypus populations in the upper reaches of this river. 

P IS FOR PLATYPUS

A number of businesses help support the work of the Australian Platypus Conservancy by donating a percentage of their profits from the sale of products or services.

The latest group to help platypus research and conservation in this way is Ashleigh Hoyle Design.  The APC will receive a contribution for each “P is for Platypus” wall sticker sold. The stickers are printed on wall vinyl with eco inks, measure 137 mm in height, and are both wipeable and removable.  For more details or to order the stickers, go to:

www.mmisforme.com.au/shop.html

(PLEASE NOTE: This product is NOT directly available from the Australian Platypus Conservancy.)