BUSINESS is drying up for the Wolvi district red claw crayfish industry, as the normally lush area faces one of its longest dry spells.
Bill and Rhonda Keast spent six months researching the area, including Bureau of Meteorology rainfall data, before settling on Wolvi as an ideal area for redclaw aquaculture.
“One of our drivers was it was wet here,” Bill said yesterday. “But it’s been a long dry spell.”
HIGH AND DRY: Redclaw farmer Bill Keast sits on the jetty and contemplates his dry crayfish ponds. Photo: Tanya Easterby
As the Queensland drought reaches in to one of the wettest coastal areas in the south-east, Mr Keast’s business is looking at lean times.
“In February last year we had 487mm of rain, but we’ve only had a drizzle since,” he said as he showed the dry ponds at his Ironbark Redclaw operation in Verne Rd.
Last month’s rain came to only 3mm, compared to 374 in January last year.
“We’ve got big ponds and 15 are empty. We’re having to empty some ponds to fill others.”
BILL and Rhonda Keast are praying for rain as much as anyone in the parched interior of the state.
Their Wolvi aquaculture operation will quickly recover if rain comes soon, but things will be grim if the dry goes on much longer.
“Maximum growth and breeding is in summer, but we sell constantly throughout the year.
Now as the water diminishes and it’s time for next year’s generation, we’re stuck,” he said.
“We’re having to shift water around and water quality is becoming harder to maintain.
“In aquaculture, water quality is everything,” he said.
With fewer ponds in operation, the remaining ponds are more heavily stocked than usual and there are limits to how long that can continue.
“Because we’re not turning over our water as much, control of water quality is taking up most of our time.
“Having ponds so dry means they are susceptible to cracking and leaking and that needs rain too.
“After a while it expands and it’s not all bad.
“It rejuvenates the soil and stops disease cycles.”
But that, as they say, is looking on the bright side.
They can restock quickly thanks to new breeding technology, but that will not help unless it rains soon.
A MELBOURNE-based PhD student is assessing the conservation risk for freshwater fish in the Kimberley in the belief many are in danger of extinction but are not listed as threatened.
This Prince Regent Hardyhead (Craeterocephalus lentiginosus) is also endemic to the Kimberley region. Photo: M. Le Feuvre/J. Shelley
University of Melbourne PhD student Matthew Le Feuvre says 50 of Australia’s 250-odd freshwater fish species live in the Kimberley and about 18 are only found in the region.
He says about 20 per cent of the country’s freshwater fish are listed as threatened by the Commonwealth Government but none of those are from the Kimberley.
Mr Le Feuvre has spent six months in the Kimberley studying freshwater fish in the last year and a half, focusing on the northern and eastern parts of the region and predominantly between the Ord and Prince Regent rivers.
The project has mainly surveyed rivers with road access but the research team has also used a helicopter to fly into more remote areas.
Some of the rivers have only been surveyed once, in the 1970s.
Mr Le Feuvre says “very, very little” is known about freshwater fish species endemic to the Kimberley.
He points to the Mitchell gudgeon, a fish found only within 10km of river either side of the Mitchell Falls, as an example of a species at risk.
“If there was development in that region or rainfall levels changed with climate change and those sorts of processes it might mean that species could get wiped out very easily,” Mr Le Feuvre says.
“Then there are other species that are found in single river systems such as the long-nose sooty grunter, which appears to be an entirely piscivorous fish, so it just eats other fish.”
Mr Le Feuvre says the Kimberley is an incredibly biodiverse part of Australia and we have a “unique opportunity” to study it before any major development happens.
As well as collecting data about the distribution and abundance of freshwater species, Mr Le Feuvre is studying the fishes’ diet, life history traits such as growth rate, age of reproduction and longevity and their ability to respond to climate change.
He is using a “triple jeopardy” hypothesis to determine the risk of extinction.
This means a species is considered to be at the greatest risk if it is range-restricted, is not very abundant where it is found and has specialised dietary, habitat, physiology or reproductive requirements.
“With those three factors against them they may be at incredibly high risk of extinction,” Mr Le Feuvre says.
“It makes intuitive sense but very few people have managed to actually empirically test that.”
COMMUNITY groups and schools are being encouraged to host an event for the inaugural Connect to Your Creek Week.
Community groups and schools are being encouraged to host an event focused on their local creek.
Healthy Waterways chief executive Julie McLellan said the aim of the campaign, from May 17-25, was to improve waterway health by increasing community stewardship of local waterways so people valued and cared for their local creek.
“Throughout the week, there will be a variety of events across South East Queensland to celebrate the diversity and beauty of our waterways,” she said.
“We encourage all community groups and schools to join us by hosting an event focused on their local creek.”
Examples of events that groups might host include tree plantings, kayaking tours, litter cleanups, guided walks, documentary screenings and workshops.
People have until February 24 to register their interest in hosting an event by completing the online form at http://www.healthywaterways.org.
Environment Minister Andrew Powell said the Queensland Government was proud to partner with Healthy Waterways on the exciting new initiative.
“One of the many reasons people love living in Queensland is our beautiful environment and our outdoor lifestyle,” he said.
“In south-east Queensland our waterways play a major role in the way we enjoy ourselves outdoors. Whether it’s visiting a cafe near the Brisbane River or taking a family camping trip near a favourite creek or waterhole.
“I look forward to celebrating our connections to our favourite waterways and attending some of the Connect to your Creek Week events.”
Australian Smelt (Retropinna semoni) are a small schooling freshwater fish found in south eastern Australia. This fish is a species complex and it appears that the Victorian population has been deemed significantly different enough to warrant it’s own species status; the Southern Smelt (Retropinna victoriae).The fish are semi-transparent so with strong backlight much of the internal details of the fish can easily be seen. These fish were filmed in the Cann River in east Gippsland.
URBANISATION, habitat degradation and waterway barriers have led to decreased numbers of native fish in NSW waterways in recent years, but programs by the Department of Primary Industries (DPI) have worked on restocking fish in these areas.
Native fish fingerlings ready for release.
Under constant threat of having their habitat destroyed, native fish have needed a helping hand from organisations such as the DPI and Landcare to increase numbers as well as improve recreational fishing opportunities.
NSW DPI fisheries management officer Ben Doolan, Nelson Bay, said close to three million trout and salmon and two million native fish, produced by government and private commercial hatcheries, were stocked into inland NSW waters each year.
“There are four species of salmonids, which are rainbow trout, brown trout, Atlantic salmon, brook trout, and four native species, which includes Australian bass, golden perch, Murray cod, silver perch, stocked for recreational fishing,” he said.
“Trout cod and Macquarie perch are stocked for conservation purposes to aid in the recovery of those species.”
Typically, four hatcheries provide fingerlings, also known as fry, for restocking.
The Port Stephens Fisheries Institute hatchery produce Australian bass, which are released into major impoundments along the east coast including Glenbawn Dam, Glennies Creek Dam and Lostock Dam in the upper Hunter Valley, Tallowa Dam near Kangaroo Valley, and Lake Wallace and Lake Lyell near Lithgow.
Mr Doolan said during restocking seasons, which varied for each species of fish, there were no restrictions for recreational fishers.
“We aren’t usually too concerned about recreational fishers being in the vicinity of newly released fish,” he said.
“The fry or fingerlings are not susceptible to recreational fishing due to their size and are mobile and will find suitable habitat.”
However, closed fishing seasons for some species have been implemented to reduce pressure or interaction with mature fish during times of spawning.
“Some species are closed for a period of time during the year, however trout cod and eastern freshwater cod are protected all year round and must be released if caught,” he said.
“There is a closure on all forms of fishing in the Murray River between Yarrawonga and Tocumwal for added protection during the (trout cod) breeding season and throughout the Mann River and some of its tributaries during August and October for eastern freshwater cod.”
Mr Doolan said these closures were primarily implemented to protect the adult fish, although the trout and salmon closure protected juvenile trout as it stopped recreational fishers wading in rivers – an activity which could disturb eggs attached to stones or gravel.
While the rivers of northern Australia and the Murray-Darling Basin are renowned for their iconic, large-sized, fish species such as Murray Cod and Barramundi, the temperate inland waterways of Tasmania are home to numerous “minnow-type” fishes.
About as big as they get: a female Golden Galaxias. Photo: Scott Hardie
Many of these species belong to the family Galaxiidae. In fact, the island state is a hot-spot for “galaxiid” diversity with 16 species (including 11 endemics). Galaxiids dominate the freshwater fish fauna of Tasmania (making up 64% of native fish species). While they don’t provide much sport for anglers, they are important components of its iconic freshwater ecosystems. These include glacial lakes such as Lake St Clair, the deepest lake in Australia, and the wild west coast rivers such as the Franklin.
The life cycle and habitats of galaxiid fishes vary, with both migratory “diadromous” and non-migratory species. Some species use either strategy depending where they live.
In Tasmania, migratory species typically inhabit streams as adults and move to the lower reaches of rivers and estuaries to breed in late autumn. They scatter a few thousand eggs over aquatic vegetation or rocks in the shallows. Their larvae grow in estuarine and near-shore marine areas and migrate back into freshwater as schools of juveniles, known as whitebait.
Non-migratory species complete their life cycles in lakes and lagoons, and typically produce fewer eggs (hundreds not thousands). Like overly-protective parents, non-migratory Paragalaxias species carefully attach adhesive eggs to the undersides of rocks along lake shorelines and guard them for up to a month until they hatch. The larvae of some non-migratory species live in open water until they are big enough to require refuge from predators, after which they seek shelter amongst rocks and aquatic plants.
While some Tasmanian galaxiids can live for up to 10 years, most live to less than three years. All endemic galaxiids to Tasmania have limited distributions. This along with habitat alterations and their relatively low fecundity, short life-span, small-size and inability to coexist with introduced fish has led to the demise of several species.
Brown trout are a significant threat to Tasmania’s galaxiids. Photo: Scott Hardie
According to Commonwealth listings, the Arthurs Paragalaxias (Paragalaxias mesotes), Clarence Galaxias (Galaxias johnstoni), Golden Galaxias (Galaxias auratus) and Swan Galaxias (Galaxias fontanus) are Endangered. The Pedder Galaxias (Galaxias pedderensis) is Extinct in the Wild.
The distributions of these species are highly restricted and some are contracting. Their populations are also fragmented.
For example, the Arthurs Paragalaxias occurred naturally in two lakes in the central highlands, but since about the mid-1990s this has declined to one lake.
The Swan Galaxias has several highly fragmented populations in headwaters of the South Esk Basin and Swan River. These are thought to be remnants of a much larger natural range.
The Pedder Galaxias is lucky to still exist: its sole natural population in the impounded Lake Pedder has gone, but the species persists in two translocated populations in south-west Tasmania.
Threats
The threats faced by the five most imperilled Tasmanian galaxiids are, unfortunately, the same threats faced by the whole group.
Introduced fish species, especially the aggressive Brown Trout, threaten all of these fishes. They have been implicated in further restricting the distributions of the Clarence Galaxias and Swan Galaxias, and causing the decline of the Pedder Galaxias.
Altering water levels in lakes for hydro-power or water supply purposes can impact breeding of the non-migratory species. It can even dewater their incubating eggs, and degrade their preferred habitat along the shore. This threatens species such as Arthurs Paragalaxias and Golden Galaxias, and likely contributed to the decline of the Pedder Galaxias.
The eggs of galaxiids can be dewatered when water levels fall. Photo: Kevin Macfarlane
Climate change will probably add to the galaxiid’s woes, with projections suggesting water running into lakes will decline.
Strategy
Fortunately, several strategies are in place to help conserve the Tasmanian galaxiids. Action under recovery plans has included population monitoring and translocation. In fact translocation saved the Pedder Galaxias from extinction.
Recent research into the ecology of several galaxiid species and impacts of changing water levels has provided a basis for managing lake water. Proactive manipulation of water levels has also been used to assist breeding of Golden Galaxias during droughts.
Keeping trout out of some waterways will be crucial for the survival of Tasmanian galaxiids. Fishery Management Plans for recreational trout fishers promote the importance of maintaining trout-free waterways.
Falling water levels leave less habitat for fish. Climate change could make things worse. Photo: Scott Hardie
Conclusion
The Tasmanian galaxiids highlight the plight of many small and endemic fish in Australia — it’s not fishing that’s the problem, but many other human activities that threaten the fishes and their habitats.
Recent work by scientists and fishery and lake managers has led to the recovery of some species and protection of others. Continuing to advance scientific understanding and refine management prescriptions will safeguard threatened galaxiid populations as their circumstances change.
The Conversation is running a series on Australian endangered species. See it here.
Scott Hardie receives funding from the Tasmanian State Government and Hydro Tasmania. He works for DPIPWE and also as a private consultant. He is affiliated with the University of Tasmania.
NEARLY one year into a study on the three rarest fish species in WA’s south-west zone is already yielding invaluable data to aid in developing action plans that may save their future.
Balston’s pygmy perch (Nannatherina balstoni) is one of the three rare fish species being studied. Photo: Stephen Beatty
The three target species are: the trout minnow(Galaxias truttaceus); Balston’s pygmy perch(Nannatherina balstoni); and the recently described little pygmy perch (Nannoperca pygmaea), which may be the rarest freshwater fish in Australia.
Murdoch University Freshwater Fish Group & Fish Health Unit researchers Dr Stephen Beatty and Dr David Morgan discovered the little pygmy perch in Denmark in 2009.
Dr Beatty says previous research had revealed serious knowledge gaps, particularly about the little pygmy perch, so the aim of this project is to develop a prioritisation list of on-ground actions for all three species.
Such actions include: protecting refuge pools; potentially recommending areas for rehabilitation and vegetation repair; and developing a list of things like in-stream barriers that may be impacting the ecology of the species’ spawning migration.
Dr Beatty says these methods have so far proven to be very successful, for example, data collected by Dr Morgan on the western trout minnow in previous years resulted in the construction of a vertical slot fishway on the Goodga River to increase its habitat.
However, Dr Beatty says these results come after copious effort.
“We do refuge pool mapping and ground-truthing; which means hiking into different pools and finding out whether different species are using them as refuges,” Dr Beatty says.
“Quite often, with these somewhat remote systems, [you really need to] hover above in a helicopter in order to document a habitat—and then go back and actually walk into them.”
Dr Beatty says the team has the least amount of knowledge on the little pygmy perch, and gathering robust data is essential so that it may be considered for the critically endangered list.
“But in the first year of sampling we already think it has to retreat into the Hay River from the Mitchell River,” he says.
“And it’s really restricted [about 95 per cent of the population] to one river pool which is only about 100m long, which makes it very vulnerable to anything that may happen to that one pool.”
Some of the issues in these areas result from feral pigs, which can damage the banks and defecate in the water.
However, Dr Beatty says the most important aspect is to ensure that groundwater abstraction does not potentially dry up these habitats.
Notes:
Funding for the project is largely from the Western Australian Government’s State NRM and the project involves key partners including the Department of Parks and Wildlife, South Coast NRM, South West Catchments Council and Blackwood Basin Group.
Stephen Beatty and team (David Morgan, Paul Close, Mark Allen, Alan Lymbery, Rebecca Davies, Tom Ryan and Craig Lawrence) presented “Enhancing the prospects for south-western Australia’s rarest and most threatened freshwater fishes” at the Inaugural Western Australian Freshwater Fish Symposium in November.
Researchers have revealed the antics that hatchling crocodiles get up to when they think they are not being observed.
While some species use quite violent techniques to prove their dominance, others seem to be quite refined and gentle, says first author of the study, PhD student Matthew Brien from Charles Darwin University.
The shocking truth about how these young saltwater crocs behave after dark has been revealed. Photo: Jemeema Brien.
The research supported by Wildlife Management International is published today in PLOS ONE.
Little is known about the behaviour of crocodiles especially in their first year or two of life, says Brien.
Because hatchling crocodiles are so vulnerable to prey, they are more secretive and harder to observe than adults.
In a previous study, Brien and colleagues used “big brother style” filming techniques to study the interaction of juvenile saltwater crocodiles (‘salties’).
“The first night we filmed, we were shocked at the level of aggression and interaction in the salties,” says Brien.
Brien and colleagues decided to extend their research to looking at the social and aggressive interactions between juveniles from seven species of crocodiles and alligators from around the world.
They studied Australian freshwater and saltwater crocodiles, the American alligator, the South American dwarf caiman, a New Guinea freshwater crocodile, an Indian gharial, and a Siamese crocodile.
Two-year study
The researchers put animals in groups of four in an enclosed tank containing an area of water and then used cameras to observe what happened throughout the day and night.
During the two-year study they found that both male and female animals tended to have aggressive interactions for short periods of 5 to 15 seconds, mostly in the water, and mostly between the hours of 4 pm and 11 pm.
“While there are certain behaviours that are shared by a lot of species, some species have their own unique behaviours,” says Brien.
For example, he says the narrow-snouted Australian freshwater (‘freshie’) avoided getting its delicate thin jaws embroiled in arguments.
“They would raise their head out of the way when they engaged in any sort of battle,” says Brien.
To show its dominance, the freshie would climb on top of other crocs and push them down, while keep its vulnerable snout out of the way.
Snout swipe
By comparison, the Australian saltwater crocodile used its broad snout to hit others over the head.
“More than any other species, the saltie would swing its head quite violently into the other like a side head strike and bite. They were by far the most aggressive,” says Brien.
Brien says these behaviours seemed to “instinctive and innate”, and were confirmed in saltwater crocodiles by comparing footage taken in the lab with that taken in the field.
“The next most aggressive was the New Guinea crocodile.”
To show its dominance, this species would raise itself up as far as its legs extended, and swish its tail violently from side to side as it chased and bit the other crocs.
“It’s basically a display to say ‘I’m coming to hurt you so you better get going’,” says Brien.
Real sweethearts
By contrast, the bizarre looking narrow-snouted gharial rarely interacted.
“The gharial are real sweethearts,” says Brien.
Juvenile alligators and Siamese crocodiles were also not aggressive.
“Siamese spent most of the time lying together and hanging out,” says Brien. “They would talk to each other, and lightly nudge or rub each other.”
Brien says such findings provide useful information for raising crocodiles in captivity.
“For example you can’t raise salties like you do alligators,” he says. “You can have more alligators in enclosures and they’re okay with each other, but salties are not as tolerant of each other.”
Knowing more about the behaviour of juvenile crocs could help optimise densities and design enclosures, for example with barriers or separate compartments, to improve survival of juveniles in captivity, says Brien.
Burrowing crayfish are a particular challenge to survey and to conserve because they live underground, and their ability to disperse is extremely limited. Sometimes this means that impacts on their habitat go unnoticed and once affected, their populations are unlikely to recover quickly.
What’s threatening the Mallacoota burrowing crayfish? Point the finger at grazing, forestry, and fishing. Photo: Jason Coughran
This series has discussed these challenges before when discussing burrowing crayfish in Western Australia and in Tasmania. The two Victorian species of burrowing crayfish that are critically endangered are the Warragul Burrowing Crayfish (Engaeus sternalis) and the Mallacoota Burrowing Crayfish (Engaeus mallacoota).
Both of these species are found in Gippsland, but one of them is a dark, glossy creature that prefers sandy soil in a remote bay near Mallacoota, while the other is a ghostly white or pale blue fuzzy specimen found in clay riverbanks in farmland near Warragul.
The site best known for the Warragul Burrowing Crayfish has been identified as Australia’s most diverse crayfish habitat because it supports four different burrowing crayfish species and at least two (possibly three) different species of spiny crayfish (Morey and Hollis 1997). I have visited this site on Labertouche Creek and it is one of the most unassuming biodiversity hotspots imaginable: a paddock that looks like any other in this part of Gippsland except for the fence that keeps the cows away from part of the river bank.
Part of the charm of burrowing crayfish is their cryptic habit — because they spend most of their time underground, most people are unaware that they are even there. Usually, Engaeus crayfish leave muddy chimneys at the entrance to their burrows which allow the careful observer to register their presence. Unfortunately, the Warragul Burrowing Crayfish often build tunnels that do not connect to the surface. This means that finding them may mean damaging their habitat by digging up a section of the river bank.
A ghost of a crayfish: the Warragul burrowing crayfish. Photo: Beverly Van Pragh
Status
The Mallacoota Burrowing Crayfish (Engaeus mallacoota) is critically endangered and is officially known from a single location in the Croajingolong National Park. However, in the last two years surveys funded by the Bushfire Royal commission have expanded the range of the species slightly. Tarmo Raadik of Arthur Rylah Institute said the number of burrows indicate that the crayfish may be locally abundant, but their limited distribution still creates a risk for the long term.
Unfortunately, the sandy shifting soils they prefer and the deep burrows they dig make these animals very difficult to collect. Counting burrows is not sufficient evidence as other (non-endangered) burrowing species overlap with their distribution, so we need better ways of collecting these little diggers.
The Warragul Burrowing Crayfish (Engaeus sternalis) is also critically endangered and until recently was known from one location on Labertouche Creek. However, the Baw Baw Shire Council did a biodiversity assessment two years ago which expanded the range of the species. Warragul Burrowing Crays have been found in the townships of Warragul and Drouin by biologist Beverly Van Praagh. She also discovered that their burrows do come to the surface and have a small chimney, but only at certain times of year.
In general, for both species, we know virtually nothing about their ecology, population dynamics or habitat requirements.
Threats
Burrowing crayfish are particularly vulnerable to local environmental disturbance. Fire, drought or large sediment pulses can drastically affect populations, especially when their distribution is as limited as in these two cases.
Even though the Mallacoota Burrowing Crayfish is found in a national park, its range includes grazing land which means their burrows can be trampled by cattle. Timber harvesting in the adjacent state forest can impact vegetation and water quality in the streams that support these crayfish. Recreational fishing is still allowed in the national park, which can pose a risk if fishers mistake these crayfish as “yabbies” and use them as bait.
The Warragul Burrowing Crayfish has a different set of issues as its environment has been subject to 100 years of grazing which has caused streamside erosion and a loss of native vegetation. Gold mining may have had a large impact, and the introduction of trout creates the threat of predation if they venture into the creeks. Given its proximity to town, it is likely that its habitat has been also destroyed by the development of infrastructure such as roads.
One of the challenges is how to conduct surveys when traditional methods (digging up burrows) are destructive and time consuming. Pitfall traps have been used to collect Warragul Burrowing Crayfish in the past. More recently, the Arthur Rylah Institute had a 10% capture rate of Mallacoota Burrowing Crayfish using specially designed burrow tube traps. In future it may be possible to use eDNA (environmental DNA) to determine what species is in a burrow just by sampling the mud at the entrance.
Education is essential for the conservation of burrowing crayfish, because we can’t take appropriate actions unless we know that these gorgeous little creatures are digging in the soil under our feet.
The community education program for the Warragul Burrowing Crayfish began in 1995 with a brochure and some fencing to protect their habitat. It has recently been expanded significantly with information signs near a giant burrowing crayfish installed on the Two Towns Trail between Warragul and Drouin. According to Greg Hollis of the Baw Baw Shire Council, further plans are underway for protecting crayfish habitat.
Some towns have giant bananas, others have giant burrowing crayfish. Photo: Greg Hollis
Conclusion
We have already come a long way in recognising and implementing conservation plans for burrowing crayfish. When I dug up my first terrestrial crayfish 20 years ago very few people knew about these engaging crustaceans. My experience in sharing information about burrowing crayfish is always positive: everyone who is lucky enough to meet one of these little guys is charmed by them.
With careful management of our rivers and wetlands we should be able to maintain these populations into the future. Their cryptic habits have a benefit – they can usually avoid predation and survive all but the most severe floods and fires without significant intervention. But we still need to manage their habitats, protect native vegetation and keep the creeks and rivers clean.
And if you get a chance, visit the Two Towns Walk in Warragul and Drouin and keep your eye out for small holes in the mud, knowing that they may lead to the elaborately branched underground world of the burrowing crayfish, a world about which we know virtually nothing.
The Conversation is running a series on Australian endangered species. See it here.
Susan Lawler has received funding from the Australian Research Council.
Original story at The Gympie Times
