The Tasmanian Giant Freshwater Lobster- the identification of significant areas to be considered for greater protection of the species. By Todd Walsh
January 2007
North West Waterwatch PO Box 303 Devonport, Tasmania, 7310
Funded by Natural Heritage Trust funds delivered through the Cradle Coast NRM Committee.
Report detailing areas to be considered for higher protection of the Tasmanian Giant Freshwater Lobster Astacopsis gouldi. Introduction The Tasmanian Giant Freshwater Lobster Astacopsis gouldi is considered to be the largest freshwater invertebrate in the world. It is found only in rivers of northern Tasmania. The Giant Freshwater Lobster is found in all Catchments that flow into Bass Strait with the exception of the Tamar Catchment. It is also found in the Arthur River Catchment, which flows into the Southern Ocean, off Tasmania’s West Coast. Today the distribution of the Giant Freshwater Lobster is more disjunct, significant declines have occurred in sections of many catchments. Large individuals are either very scarce or absent from many areas. Localised extinctions are thought to have occurred in many areas of their former range. Giant Freshwater Lobsters, by nature are shy, secretive animals. Ideal habitat is an intact catchment of several stream sizes including rivulets and small headwaters. These should flow and meander through a relatively undisturbed well vegetated catchment containing snags, pools and undercut, but not eroding, banks. Water temperature should seldom exceed 18C have high oxygen content and be clear of sediment. Giant Freshwater Lobsters are very cryptic and shy. They are slow growing, slow to colonise new areas and have a low reproductive rate. Their diet is mainly decaying wood, but leaves, fish, rotting flesh and detritus are also eaten. While little is known of their dispersal patterns, individuals have been recorded moving 500m in 24 hours. Movements over land have also been recorded. Giant Freshwater Lobsters are most active when water temperatures are higher. Female Giant Freshwater Lobsters mature after about 14 years, weighing about 500g with a carapace (body) length (CPL) of 120mm. Males mature more quickly at around 300g and approximately 76mm CPL in about 9 years. It is estimated that Giant Freshwater Lobsters may live beyond 40 years. Historically, specimens weighing 4 to 6 kg were reported, however Giant Freshwater Lobsters weighing more than 3 kg are now considered large. *Note: Females have been located in a catchment, egg laden at 85-90mm CPL. Females breed every two years, with mating and spawning occurring between March and April. The female carries the eggs under her tail over winter until they hatch in late December-January. Hatchlings stay attached until late February when they measure about 6 mm CPL. The young moult several times a year but this becomes less frequent as they get older. Juveniles have been located in shallow faster flowing areas known as riffle zones. It is suspected they migrate into smaller stream zones including semi-permanent creeks. It is in these areas that they are safer from many predators such as larger fish (blackfish, trout) and platypus, which struggle to swim in the very shallow sections. The juveniles find cover amongst the cobble rocks and woody debris and remain in this area until large enough to move into the deeper areas known as runs.
Runs are deeper flowing straight sections of a catchment. Many sub adult (<100mm CPL) have been located in these areas. It is suspected that these sub adults are not large enough to enter the domain of the adult lobsters, the deeper pools. Adults take refuge in still, deep pools, which are sheltered and well shaded beneath submerged and decaying timber. Adults can live in larger numbers (up to 20 individuals) in one large pool. Although sometimes aggressive, lobsters appear to tolerate one another in these pools. A steady increase in habitat disturbance, combined with a long history of traditional fishing has caused the decline of the Giant Freshwater Lobster. Large individuals have been targeted for eating and trophies, and this has had a significant effect on breeding stock, completely removing cohorts from some river systems. The lack of any bag limit until the 1990’s allowed over fishing to occur for many years. In 1995 the Giant Freshwater Lobster was listed as ‘Vulnerable’ on the Tasmanian Threatened Species Protection Act and the Commonwealth Endangered Species Protection Act. From 1 January 1998 it was declared a ‘Protected Fish’ under the Inland Fisheries Act signaling the immediate end of the recreational fishery. The maximum fine for taking Giant Freshwater Lobster is $10 000. There are two other lobsters in the Astacopsis family, both of which only occur in Tasmania. While there is some overlap in range, A. franklinii occurs mainly in rivers throughout eastern Tasmania and A. tricornis throughout the south and west. All Astacopsis species are now totally protected by law.
Sites of Importance to Astacopsis gouldi The priority must be to protect those sites that contain significant habitat for the Giant Freshwater Lobster. The rehabilitation of impacted areas may be a long and, in many catchments, an unsuccessful process, due to the extent and nature of the impact. Sites with relatively intact headwaters, large tracts of bushland with a variety of pools, runs and riffles and known significant populations of the Giant Freshwater Lobster would be suitable for greater protection protocols (higher reserve status and/or larger more complete buffer zones). Headwaters and other feeder streams must also contain suitable habitat to minimise downstream impacts. Disjointed reserves are not considered as desirable as large areas of catchment with protection to the uppermost headwaters. There are still large areas which would satisfy most criteria for increased Giant Freshwater Lobster protection. The majority of these areas in the Cradle Coast region appear to be in the Waratah-Wynyard and Circular Head municipalities. Each area will be discussed in detail and protection measures suggested.
Arthur Catchment The Arthur Catchment is one of the largest catchments in the Cradle Coast Region, covering an area of approximately 2500 km2. The main waterway is the Arthur River, which rises at an altitude of 800 m to the south west of Mount Bischoff, near the township of Waratah, and flows over 180 km to enter the Southern Ocean to the west of the township of Arthur River, some 20 km south of Marrawah. Significant tributaries of the Arthur River are the Frankland River (formed by the confluence of the Horton and Lindsay Rivers), which drains most of the western and lower portion of the Catchment, and the Rapid, Lyons, Keith and Hellyer Rivers in the middle and upper parts of the Catchment. These waterways make up Tasmaniaâ&#x20AC;&#x2122;s largest remaining system of wild rivers. Current land-use in the Catchment is principally forestry, with agriculture localised near the townships of Arthur River and Waratah. Historically, mining has been important and there is a legacy of acid mine drainage from the old Balfour mine, located in the Frankland Catchment, and from the Mount Bischoff mine, which has caused major problems in water quality in the upper Arthur River. Average annual rainfall across the Catchment varies between 1000 mm on the coast to 2200 mm in the upper reaches. Frankland River The Frankland River begins at the confluence of the Horton and the Lindsay Rivers approximately 22 km East of Temma. It flows into the Arthur River approximately 10km east of the township of Arthur River. The Frankland River is accessible in few areas and contains an extremely large area of excellent Giant Freshwater Lobster habitat. There has been a significant population (more than 100 specimens tagged and released in <500m of waterway since 1998) identified in the Frankland River close to a major access point. This indicates that a substantial population may be present in the inaccessible areas. The Frankland is a very deep river by north-west standards (deeper than 10 metres in places) with few or no riffle zones in the 500m site surveyed. It is extremely difficult to locate the smaller Giant Freshwater Lobsters in the Frankland simply because of the depth (juveniles do not readily accept baits). The surveyed site in this section is either deep gorge or small waterfalls, and there is one small riffle zone where one juvenile has been captured from under a rock. Given the lack of riffle habitat throughout the Frankland River, it is possible that this population is maintained by recruitment and development of juveniles in the deep habitat in which the adults live and in smaller streams feeding into the Frankland River main. The river has a huge area of habitat (depth, bottom surface area and vast amounts of large woody debris) and would provide significant habitat for Giant Freshwater Lobsters. Giant Freshwater Lobsters in the Frankland River and the Keith River (both Arthur River tributaries) become sexually mature at a much smaller size than those surveyed elsewhere. The Giant Freshwater Lobster is reported to become sexually mature at
120mm CPL (Hamr 1990). A breeding female has been captured in the Frankland River with a CPL of 105 mm, and four females carrying hatching eggs have been captured in the Keith River with a CPL of <90 mm. It is recommended that this be investigated further as it is highly unusual and could possibly indicate a subspecies. The Frankland River has predominantly blue Giant Freshwater Lobsters. The Arthur Pieman Protected Area borders the Frankland River; however the Frankland River is not included in the Arthur Pieman Protected Area. Recommendations
Extension of the Arthur-Pieman Protected area to 300m east of the Frankland River at Blackwater Road and upstream would give significant protection to a large sub Catchment and population of Giant Freshwater Lobster. The extension of the Arthur Pieman Protected Area to 300m east of the Leigh River to its headwaters, would give significant protection to a large headwater tributary of the Frankland River. A 200m buffer along the lower Frankland River from Blackwater Road Bridge to the confluence with the Arthur River would also offer significant protection to a large population of Giant Freshwater Lobster.
Rapid River and Little Rapid River The Rapid River rises approximately 8km east of Mount Bertha and is just west of the Savage River National Park. The Rapid River joins the Arthur River approximately 5km southwest of the Milkshake Hills. The Little Rapid River rises at the southwest corner of the Wynsmith Hills and joins the Rapid River 2km south of Luncheon Hill. These 2 rivers have not been surveyed to any extent as yet. There has been a small survey carried out on the Rapid River (2000) and, although there would be some illegal taking of Giant Freshwater Lobster from both rivers, there would be a high chance of a significant Giant Freshwater Lobster population in each. These 2 rivers have extensive tracts of bushland with no industry impact other than forestry. Recommendations
A large buffer zone on each waterway (100m either side) at and upstream from the confluence of both rivers would give significant protection to a large sub catchment and population of Giant Freshwater Lobster. Class 3 streams upstream from the confluence would benefit from 50m buffers and Class 4 streams from 30m buffers.
Keith River and Lyons River The Lyons and Keith Rivers rise near Baretop Ridge approximately 20km northwest of Waratah. They join the Arthur River 13km southwest of Preolenna. The Keith River rises inside the Savage River National Park. The headwaters of the Lyons River pass through the Savage River National Park and the Meredith Range regional Reserve. The Keith River has produced the largest number of Giant Freshwater Lobster caught in a single day’s surveying on 2 separate occasions (2000), indicating
a large population density. The CPL of the egg laden females was significantly lower than any lobsters caught in any other location. Four lobsters with eggs had a CPL of <90mm (the accepted breeding size CPL is 120mm for females). Recommendations
Extension of the Savage River National Park to the confluence of the Keith River and the Arthur River would give significant protection to a large sub Catchment and population of Giant Freshwater Lobsters. Extension of the Savage River National Park to the confluence of the Lyons River and the Arthur River is also worthy of consideration. A 200m buffer along the Lyons and Keith Rivers to the confluence with the Arthur River would also offer significant protection to a large population of Giant Freshwater Lobsters.
Duck Catchment The Duck Catchment covers an area of 542 km2 and is principally drained by the Duck River, which rises at an elevation of 200 m to the south east of Gibson Plains and enters Bass Strait at Duck Bay near Smithton. Tributaries of the Duck River include Roger River, in the upper Catchment, and Edith Creek, in the lower Catchment. Two smaller waterways, Deep Creek and Scopus Creek discharge separately into Duck Bay. The topography of the Catchment is gentle and low lying and prone to flooding during winter rains. There is a long history of canal construction in the Catchment to drain flood waters and many of the waterways have been highly modified or straightened. Rainfall across the Catchment varies between 1,100 to 1,500 mm per year. Beef and dairy farming are the principal land uses in the low-lying areas of the Catchment, with forestry becoming more important in the upper reaches. There is a significant aquaculture industry in Duck Bay, and Lake Mikany on Deep Creek provides the main water supply for Smithton. Duck River The Duck River has a history of producing very large individual Giant Freshwater Lobsters; population surveys over the previous 8 years have confirmed this reputation. The Duck River upstream from Trowutta Road Bridge has areas of significant habitat. This includes many well forested areas and wide riparian zones. Sediment levels appear low in many parts and a diverse area of pools, runs and riffle areas is found in the surveyed area, and would be expected to continue upstream. A large and diverse population of adults and juveniles (150+ individuals recorded) has been surveyed in an area less than 1km in length at the site DU1 (1998-2007). The Duck River has also been surveyed near Lileah and was also found to have significant habitat for Giant Freshwater Lobster.
Recommendations
The upper Duck Catchment is a significant area that would benefit greatly from higher protection status. Higher protection in the form of larger buffer zones along the main river and all tributaries (especially headwaters) upstream from Trowutta Road Bridge to all headwaters would significantly assist populations in the region. The establishment of conservation areas in the upper Duck Catchment could also be considered.
Black-Detention Catchment The Black–Detention Catchment is over 600 km2 in area. Apart from the Dip Range, which forms the eastern boundary of the Catchment and rises to an altitude of about 500 m, most of the Catchment is below 250 m. Average annual rainfall across the Catchment can vary between 900 and 1,600 mm. The southern and western parts of the Black-Detention Catchment are drained by the Black River and its major tributary, the Dip River. These two rivers rise on the south western slopes of the Dip Range and flow into Bass Strait at Sawyers Bay to the south of Stanley. The eastern part of the Catchment is drained by the Detention River, which flows into Bass Strait at Hellyer. There are also a number of small creeks and streams that discharge directly into Bass Strait. The main land uses in the Catchment are forestry and tree farming in the upper reaches, while the flat coastal areas are predominately used for grazing and cropping. Some of the tributaries of the Black River have been heavily impacted by human activity. Black River The Black River rises less than 1km from the headwaters of the Hebe River (Inglis Catchment) in Dip Range. The estuary of the Black River is one of the least impacted estuaries in the Cradle Coast Region and is considered to have “critical conservation significance” (Edgar et al., 1999). The Black River predominantly flows through State Forest and has low direct agricultural impact. This is significant as almost all the major waterways in the Giant Freshwater Lobsters range are impacted by mining or agriculture (historically or present). The Black River is possibly the least impacted of all the major rivers that contain the Giant Freshwater Lobster. The health of the Black River has been measured at 3 sites (2 AUSRIVAS sites 2004-2006) and the river is considered to be very healthy. Good water quality, a lack of sediment and high densities of in stream woody debris also highlight the Black River to be a major Giant Freshwater Lobster waterway. The Black River was not surveyed in this period, due to accessibility and OH&S issues (the Black sites have only been successfully surveyed by canoe previously). Previous surveys of the Black showed a large healthy population of Giant Freshwater Lobster in a small surveyed section of the River.
Recommendations
The Black River is a significant area that would benefit greatly from higher protection status. Higher protection in the form of larger buffer zones along the main river and all tributaries (especially headwaters) would significantly assist populations in the region. A 100m buffer zone on the Black River main would give significant protection to a large sub catchment and population of Giant Freshwater Lobster. Class 3 and 4 streams would benefit from 50m buffers. This would decrease the risk of sedimentation and rising temperatures. The establishment of conservation areas in the Black River should also be considered to maintain a large population in high quality habitat.
Dip River The Dip River has been heavily fished in the lower sections; but the river habitat is in relatively good condition near the junction with the Black River. The Dip headwaters are in excellent condition and have produced the largest individual captured for many years (4.5kg male 2006). Recommendations
The headwaters of the Dip River to be included in a larger protected area which joins the Dip Range Regional Reserve. The Dip River could also be protected by expanded buffers and protected status until its confluence with the Black River.
Dip Range Dip Range is a relatively small range of significant importance to the Giant Freshwater Lobster. The remote and inaccessible headwaters of the Black, Hebe (Flowerdale Catchment) and Detention Rivers occur within a 5 km radius. Dip Range is possibly the most important Giant Freshwater Lobster headwater region. Many headwaters within the lobster’s range have been heavily impacted. It is vital that the remaining remote headwaters are highly protected. Recommendations
The status of Dip Range (currently a regional Reserve) could be upgraded and expanded to protect the headwaters of the Black, Hebe and Detention Rivers.
Inglis Catchment The Inglis Catchment covers an area of approximately 600 km2. The two principal waterways are the Inglis River and the Flowerdale River. These two rivers merge at the township of Flowerdale, only a few kilometres upstream of Wynyard where they flow into Bass Strait. The Inglis River rises to the south west of Oonah, in the extreme south of the Catchment. The Flowerdale River rises in the southwest of the
Catchment and its main tributary is the Hebe River. Several smaller creeks, including Sisters Creek, Camp Creek and Seabrook Creek drain directly into Bass Strait. Annual rainfall in the Catchment ranges from about 1000 mm at the coast to greater than 1600 mm in the upper Catchment, some 26 km inland from Wynyard. Land use in the Catchment is dominated by extensive plantation development in the south and west, while agricultural activity is heaviest in the area between Takone, Yolla and Wynyard. Many of the creeks in the agricultural areas are highly modified and degraded. Significant areas of native forest still remain in the mid Catchment, largely due to the steep topography. Between 1999 and 2002, DPIWE carried out a study on the state of waterways in the Inglis Catchment (Bobbi et al., 2003). They found that much of the Flowerdale River and the headwaters of the Inglis River were in good environmental condition, but conditions in the lower sections of the Inglis River and in the smaller waterways in the north and east of the Catchment were relatively worse, with poorer water quality and more degraded in stream and streamside habitat. In some situations, these were causing significant impacts on the health of the aquatic ecosystems of the Catchment. Major management issues listed in the report were the removal of riparian vegetation and continuing impacts of sediment and nutrient delivery to waterways in the middle and lower parts of the Catchment. Recommendations for improved management included improved protection and rehabilitation measures for riparian zones, better management of runoff from gravel roads and extraction pits, and decreased erosion and run-off from areas of intensive agriculture. Flowerdale River The Flowerdale River rises near West Takone in a plantation area at the southern edge of Campbell Range. The plantation area is at the very top end of the Flowerdale catchment and impacts on a small area of headwater. The Flowerdale River flows predominantly through State Forest until Lapoinya Rd Bridge. It then flows through agricultural land until the confluence with the Inglis River at Flowerdale. A section of the mid Flowerdale Catchment has been extensively surveyed since 2000, with almost 200 Giant Freshwater Lobsters tagged and released. The most Giant Freshwater Lobsters exceeding 3kg have been captured at this site. The section surveyed has extensive pools, runs and riffles. Many juveniles have also been tagged and released at this site. Water quality and AUSRIVAS monitoring have been undertaken at the upper Flowerdale River site at Meunna Road Bridge. Juvenile Giant Freshwater Lobsters have been located at this site, which is in excellent condition. The Flowerdale River appears to have a large area of excellent habitat for Giant Freshwater Lobsters. Large populations and individual specimens have been consistently recorded in only a small section of the river (2000-2007), indicating the possibility of a substantial population. Recommendations ď&#x201A;ˇ
Higher protection in the form of 100m buffer zones along the main river and 50m along all tributaries in State Forest upstream from Lapoinya Road Bridge would significantly assist populations in the region.
The establishment of conservation areas in the Flowerdale River should also be considered to maintain a large population in high quality habitat.
Hebe River The Hebe River rises in Dip Range approximately 2km NE of Mount Dipwood. The Hebe joins the Flowerdale River in State Forest, approximately 2km NW of Preolenna. The Hebe River is a major tributary of the Flowerdale and is relatively unimpacted. The Hebe is easily accessible in few areas and has excellent Giant Freshwater Lobster habitat. A section of the Hebe River was surveyed on January 11 2002. This site was given a total score of 21 out of a possible 22. The site has one point deducted due to an old beer can (ring pull VB, indicating an age >10 years) being found in the bush near the site, indicating a very small possibility of fishing pressure. A site on the Hebe River was extensively surveyed from 2002-2004 with almost 50 Giant Freshwater Lobsters captured including some larger specimens. Water quality and AUSRIVAS monitoring have been undertaken at the mid Hebe River site at Myalla Road Bridge (2005-2006). Juvenile Giant Freshwater Lobsters have been located at this site, which is in excellent condition. The Hebe River appears to have a large area of excellent habitat for Giant Freshwater Lobsters. A relatively abundant population has been recorded in only a small section of the river, indicating the possibility of a substantial population. Recommendations
Higher protection in the form of 100m buffer zones along the main river and 50m along all tributaries upstream from the confluence with the Flowerdale River would significantly assist populations in the region. The establishment of conservation areas in the Hebe River should also be considered to maintain a large population in high quality habitat.
Conclusion The Tasmanian Giant Freshwater Lobster is an iconic species of Northern Tasmania. To date, very little specific protection measures have been implemented to assist in the recovery of this nationally listed species. This report reinforces recommendations of previous reports that targeted protection of significant water bodies from designated points to the extreme upper headwaters. It is of vital importance that these measures be considered and action taken within a nominated time frame. It is extremely significant to note, that the first report detailing important areas for habitat protection was released 10 years ago. To this day, not one of these protection measures has been implemented. There are 19 catchments within the original range of the Tasmanian Giant Freshwater Lobster, 13 in the Cradle Coast NRM region and 6 in the Northern NRM region. Today only 5 Catchments would be considered to have significant areas (whole catchment/large sub-catchment) of excellent habitat including headwaters for the Tasmanian Giant Freshwater Lobster. None of these catchments are in the Northern NRM region, which is a particular source of concern.
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