Handling crayfish in Blue Mountains canyons

Post Reply
User avatar
T2
Site Admin
Posts: 235
Joined: 15 May 2018, 10:33
Full name: Tim Vollmer
City: Blaxland
State: New South Wales
Contact:

Handling crayfish in Blue Mountains canyons

Post by T2 » 06 May 2019, 09:50

Tim Williams (canyon guide, owner of guiding company Wilderness Adventures, and fourth generations Blue Mountains local) has kindly given me permission to reproduce the following post he has written about how canyoners should interact (both legally and ethically) with the crayfish that live in most Blue Mountains canyons. He has provided a range of links at the end for those interested in further reading.

There have been a number of heated discussions regarding the handling of Crayfish in Blue Mountains canyons. I’d like to share the info I’ve collected over the years on these beautiful creatures and explain the regulations which govern their handling and capture in NSW.
I’m explaining the regulations first so that the legal framework is clear. I’m not writing this post because I think the legal framework should be the focus (or is evidence based). However, I think it’s important to understand what the law says before canvasing other details about these creatures.

Regulations:
In NSW Crayfish are managed/regulated by the Department of Primary Industries (DPI) under the Fisheries Management Act. Even if the crayfish are within a National Park or reserve, they are still managed by DPI Fisheries.
In NSW there is only one species of freshwater crayfish which is totally protected from fishing Euastacus dharawalus (Fitzroy Falls Spiny Crayfish) which is found in one small creek which feeds Fitzroy Falls.
The other species of Spiny Crayfish found in NSW (including the species found in Blue Mountains Canyons) may be kept and eaten by fishers with a current recreational fishing license (or license exemption), provided the crayfish are of legal size and are not carrying eggs.
All undersize crayfish and those with eggs must be returned to the water unharmed. It is illegal to remove the eggs.
The legal size for all Spiny Crayfish (except Murray Crayfish) is 9cm OCL.
OCL means the length of the carapace, as measured from the rear of the eye socket to the centre rear of the carapace.
Spiny Crayfish cannot be taken in notified trout waters (e.g. Cox’s River upstream of Little River to it’s head waters).
Bag Limit: (one or more species) 5 (only 1 over 12cm OCL)
Possession Limit: (one or more species) 10 (only 1 over 12cm OCL)

Researcher presentation:
Some years ago I attended a presentation at the Blue Mountains City Councils Waterways Festival by Australia’s leading expert on Freshwater Crayfish (Robert McCormack). I kept a few notes, which I have used to write the next section of this post.
Rob has conducted research on Crayfish in the Blue Mountains over many years, he literally wrote the book on Spiny Crayfish, he has identified more cray species than any other researcher in the past 40 years and he helps run the Australian Crayfish Project.
During his talk and in his book, he discussed in detail the breeding cycle of Spiny Crayfish and how these animals should be handled. As a researcher he has to gain ethics approval for studies and has looked in detail at the risk of handling crayfish, particularly those with eggs or live young attached.
He talked about how he catches Crayfish using fish (tuna) on a rope as bait.
He talked about them having a mostly vegetarian diet, but being opportunistic carnivores and cannibals. They come quickly to a fish bait.
Rob did not convey concerns about people handling crayfish provided they handled them appropriately and they did not intentionally remove eggs. He was very clear that they handle being out of the water for periods very well as long as they remain wet.
He showed many photos of researchers holding berried females.
He was clear that over fishing, particularly illegal fishing (taking of undersize or berried females) was a major population risk.
I don’t remember him talking about a risk of eggs falling off while handling crayfish, however he did talk about females naturally flicking the eggs from the tail before or after the eggs have hatched to disperse the young throughout a pool. I’m not suggesting it’s not a risk. I just don’t think it was discussed.
He talked in great detail about the excellent breeding capacity of Crayfish and that the research was not a risk to the Crayfish populations. He talked about some females then beginning to eat their own young almost immediately after flicking them free of the tail.
He talked about the way they produced far more offspring than the creek can sustain. He also said they have very high mortality rates due to predation and high competition for resources.
Rob discussed identifying crayfish gender from features on their legs and using the number/size of spines on their front leg segments to identify between species.
He showed how to identify the two species found near Katoomba and in most Blue Mountains Canyons.
These are:
Euastacus australasiensis ( Sydney Spiny Crayfish) – This species is not likely to grow much beyond 6cm Carapace Length. They often burrow around hanging swamps, seeps and vegetated banks.
Euastacus spinifer (Giant Spiny Crayfish) – This is a true Giant Spiny Crayfish and can grow very large. They burrow near/in creeks and in streamside vegetation.
I suggest reading Robs book for detailed identification descriptions of these two species. Particularly the differences in “dorsal propodal spines”
Euastacus spinifer are by far the largest of the two species as the name suggests. They are highly aggressive and territorial.
They are opportunistic omnivores mostly eating organic material. They are also predators, and when the opportunity arises, cannibals as mentioned above.
Males mature at 5 years (min 45mm Carapace Length)
Females reach maturity around 8 years (min 60mm Carapace Length)
The largest specimens recorded are about 40 years old and they may grow to 50 years old.
They can attain weights up to 2kg and over 160mm Carapace Length in extreme cases.
A healthy creek system will be able to sustain a fairly static biomass of Crayfish. Once the crayfish numbers reach capacity in a pool, no additional crayfish can enter or join that population. When all things are in balance pools reach a static population level and remain at that level. Over fishing, chemical pollution, predation and sedimentation can reduce the population rapidly.
I have recently read a study Rob completed at Wentworth Falls which showed that most sample sites near Darwin’s Walk have recovered well from the poisoning event a decade ago and crayfish population has returned to the creeks capacity. The capacity seems to be less than 30 crayfish per sample site.
Unlike Yabby’s they do not survive well in lakes, dams or other non flowing water bodies. They prefer flowing well oxygenated water. They do not grow substantially faster in an aquiculture system and are not suitable for commercial growing due to their very slow growth rate.
Large Crayfish are often the dominant predators in the water within Blue Mountains canyons. The larger the crayfish grows the less susceptible it is to predation from eels and other predators.

Here are some other facts I’ve gathered about crayfish over the years. I’ve used these when talking to clients when guiding canyons.
Crayfish are a type of Arthropod and are distantly related to other crustacea such as prawns and crabs. The oldest fossil record of a crayfish is over 280 million years old, but they are likely to have been around for almost 500 million years.
All Australian freshwater crayfish species belong to the Parastacidae family. In NSW most crayfish species belong to the genera Euastacus. These are spiny crayfish of the Great Dividing Range. They have two rows of spines on each claw. These spines are not found on Yabby’s (Cherax) which have smooth claw shells on the lateral side.
In Blue Mountains canyons there are two common species of crayfish. Though a third can be found in the Wollemi in the upper reaches of the Cudgegong River.
Euastacus australasiensis occurs in streams and upland swamps (including hanging swamps). They are found from near sea level to 1200m altitude.
Their burrows can be seen in Blue Mountains creek side banks/vegetation, hanging swamps and with seepage along bases of moist cliff-lines. They are common in canyons.
This species is capable of overland movement and is usually coloured orange or red.
Euastacus spinifer are true Giant Spiny Crayfish. They are found from near sea level to 1200m altitude. They are highly variable in colour and may be blue, green, red, orange or a combination of colours. The colour often changes with habitat and sometimes take a similar orange colour to Euastacus australansiensis in Blue Mountains canyons. This species is known to forage overland.
They breed in May to July and can have 200 to 1500 eggs. 800 on average. They carry eggs under their curled tail. The eggs sit between thin gills until they hatch or fall off. While carrying eggs, the mothers are described as “berried”, maybe because the eggs look like a bunch of bright berries hanging from the tail.
Newly hatched crays may remain under the tail consuming the remains of the egg or until the female shakes the young/eggs free from the tail.
Mortality of juvenile crayfish is very high. They are easy prey. Even the mother will eat them immediately or soon after shaking young free despite having carried them under her tail for many months to protect them.
Crayfish moult as they grow. Five times in the first year, twice in the second year and once a year proceeding that.
Once they have a well-established burrow they can have a long breeding life ahead of them.
Once they reach 300g they are mostly immune from predation and are often the dominant predator of their chosen pool, but when small they are easy prey for eel, platypus, water rat, water birds, bass and larger crayfish.
Their diet is varied. Mostly they forage on detritus, aquatic macrophytes and algae; hunting for small aquatic animals (e.g., insect and frog larvae, juvenile crayfish); or interacting (sometimes aggressively) with their relatives in shallow streams.
The mouth has six appendages (in pairs called maxillipeds) which allow them to eat almost anything. The two largest maxillipeds are called the third maxillipeds and are situated at the base of the mouth and are most important as they help crayfish burrow, clean themselves, catch/hold food and much more. The other two pairs of maxillipeds are smaller.
Crayfish are decapods, which means they have 10 legs including their claws. The legs which form the claws have four sections and it’s the spines on these sections which are usually used to identify different species of spiny crays.
The second set of legs have smaller nippers, with hairs that smell, taste and sense food.
They can regrow limbs if lost in battle or accident. Though it is a major disadvantaged to lose a limb. Crays missing appendages often have a shortened life expectancy. It’s not uncommon to see crayfish which have uneven or missing claws which are yet to regrow.
Crayfish have gills under their carapace, which do not collapse like fish gills when removed from water. Crayfish can survive out of water for long periods provided the gills stay moist. They often live out of the water in burrows and can feed on land, particularly after rain.
They can use the gill bailer at their mouth to draw water to the gills under the carapace. The legs act like straws during this process.
The tail (abdomen) has six segments with fine hairs underneath to which the female cements her eggs.
While the anus of a crayfish is in the tail, they expel urine from their heads just above the mouth, which is also where water passing over the gills is expelled.
Euastacus spinifer crayfish can clearly grow to a large size, are aggressive, cannibalistic and territorial.
Studies indicate capacity of creek pools is typically between 0.5 and 5 per linear metre of stream (not including crayfish under 1.5 years of age). In narrow canyons it is more likely to be closer to 0.5 per linear metre.
Once the crayfish numbers reach capacity in a pool, no additional crayfish can enter or join that population. Individual pools and the overall total creek population, when all things are in balance reach a static population level and remain at that level.
You can find individuals of Euastacus australasiensis co-habiting in pools in streams with the larger Euastacus spinifer.
E. australasiensis is less aggressive.
Breeding females can take 7-10 years (for Euastacus australasiensis) to reach sexual maturity and live potentially for several decades afterwards. Removing large, old individuals, can quickly remove the breeding population. Few, if any, Euastacus australasiensis would reach the minimum legal size. The current record is 6cm CL.
Euastacus spinifer may reach the 9cm CL legal size, but only after numerous decades of life.
It is not correct to call a Spiny Crayfish a Yabby.
The yabby (Cherax destructor) has the largest range of all Australian crayfish. It occurs across most of Victoria, western New South Wales, south-western Queensland and eastern South Australia. They are probably the most hardy crayfish. They can tolerate poor water conditions and long periods of drought by burrowing deep into the river bed or dam wall in order to stay moist. This species was named destructor because of the damage its burrowing caused in dam walls and levee banks.
It has been introduced in the Blue Mountains at locations such as Wentworth Falls Lake.
Cherax destructor (yabby) is an introduced species when found in the Blue Mountains eastern flowing creeks and poses a risk to the endemic Spiny Crayfish species. Yabbies are known to feed on juvenile spiny crayfish and grow much faster.
The Yabby is unlikely to be found in most Blue Mountains Canyons.
Yabby’s range in colour from brown, green to pale blue with mottled claws. There is no minimum legal size for yabby’s.

Other Crayfish Species:
Euastacus vesper is a newly described species that is only found in the upper Cudgegong River in Wollemi National Park.
Fiztroy Falls Crayfish
Mentioned earlier Euastacus dharawalus is NSW’s rarest spiny crayfish species and it is totally protected. Euastacus dharawalus is only found in one small stream (Wildes Meadow Creek) roughly 11 km long above Fitzroy Falls. The Falls is an 80 m straight drop and it is surmised that E. dharawalus is just a remnant population isolated from all the other species in the surrounding area by the barrier of the falls.

Here are my take outs about handling these animals in canyons:
1) If you are going to catch spiny crayfish and/or handle them, you need a current NSW fishing license or an exemption under the fisheries regulations.
2) Very few crayfish reach the legal size. They are decades old when they do!
3) Smaller crayfish (under 9cm CL) and those with eggs are totally protected. They must not be kept and should be immediately returned to the water if caught.
4) While legal to catch and keep those over 9cm CL. It’s not ideal to keep them for food. They are very slow growing. If keeping a crayfish, you are inevitably removing the older, stronger breeding stock. Overfishing can happen quickly with such slow growing animals. A small number of fishing trips could remove all “legal size” crays from a stretch of stream and it may take a decade or more for smaller crayfish to grow to “legal size”.
5) Crayfish breed from May onwards. They can carry eggs through the middle of summer. It is most common to see berried females early in the canyoning season. They disperse their eggs throughout their range. They may disperse some young after they have hatched and others before they have hatched. They often eat their own young.
6) It is unclear if handling crayfish and returning them to the water is a risk to the population or not. Research activities are seen to be of low risk. Researchers regularly trap and handle crayfish. Some with substantial numbers of eggs and it’s not clear if eggs are lost.
However, if recreational canyoners all picked up and handled crayfish it could have a much more adverse impact on the overall population (when compared to a small number of research trips). As such, in high use canyons where there are large volumes of visitors it is not advisable to pick up crayfish. In low use canyons it’s unlikely there would be an adverse impact.
7) The recovery of crayfish following the insecticide spill at Wentworth Falls shows these animals can rebuild their population if the conditions/habitat returns to a healthy state. Though it can take as much as a decade.
8) Crayfish have burrows in swamps and vegetated creek banks. These could be trampled by canyoners. Canyoners should avoid banks, swamps and try to avoid trampling visible burrows and crayfish.
9) It is legal to catch crayfish in NSW. Individuals are free to choose for themselves if they wish to catch and handle these animals, provided they comply with the regulations. Though think long and hard before posting your crayfish dinner pic's on this forum!

Some further reading for those who want it!
https://www.aabio.com.au/crayfish-list/
http://www.aabio.com.au/new/wp-content/ ... g-08-2.pdf
https://www.publish.csiro.au/book/6804/
https://www.bmcc.nsw.gov.au/sites/defau ... Report.pdf
https://www.bmcc.nsw.gov.au/sites/defau ... nation.PDF
https://bmnature.info/fauna-crayfish.shtml
https://www.dpi.nsw.gov.au/__data/asset ... st-NSW.pdf
https://austcray.com/2017/03/euastacus- ... tacus-nsw/
https://www.dpi.nsw.gov.au/fishing/recr ... s-and-regs
https://researchers.mq.edu.au/en/public ... inifer-dec
https://www.aabio.com.au/surveying-nsws ... rawalus-2/



Post Reply