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Aquatic Biological Surveys – Giant Spiny Crayfish

One of my many roles is research co-ordinator and sponsor of the Australia Crayfish Project (APC).  We have been conducting aquatic biological surveys of freshwater crayfish over the last eight years around Australia and it is one of the many projects driven by Australia Aquatic Biological run by Robert McCormack.  These are amazing aquatic creatures. [heading] Aquatic Biological Surveys [/heading] Our most recent aquatic survey was in the Southern Rivers Catchment area where we are investigating aquatic diversity across the catchment area.  It is a very large area and will take many more trips into the jungle to get a better picture of the health of the system. As you can see from the above photo, the water and the aquatic life are in great shape, even after heavy rainfall.  We collect, mostly by hand specimens from the rivers and creeks, weigh, measure and record numbers found in each of the areas.  This particular few days, it did not stop raining, so it was cold and very wet. The average size of the Euastacus spinifer (pictured above) was between 300 and 600 grams per animal.  There was another species (Euastacus yanga) there as well but it is a much smaller spiny crayfish species that appears to co-exist with these true giant spiny crayfish. Rob, measuring the OCL of this female crayfish.  This one was about 91mm.  It takes about 20 years for this crayfish to get this big and it takes about 10 years before they can breed, so any disturbance to their environment or their numbers through poaching can have devastating effects across the eco-system. As with all Euastacus species, they breed in May-June and carry the eggs and young crayfish which hatch around December.  That is a long time for a crayfish to carry eggs.  Considering the smooth crayfish, yabbies and the like only carry eggs for about 30 days. One of the tricky things with these very spiky giants is counting the eggs on each of the females.  This particular one carries approximately 400 eggs of which, only 1 in 1000 will survive to adult and breed.  The remaining young crayfish are a substantial food source for platypus, eels and native fish in the catchment so they are very important to the food chain. Every site we survey, we conduct extensive water quality tests to give us a base line indication of the health of the catchment which we can refer to in subsequent surveys. How important are these crayfish to the ecology of the catchment? Protect the rivers and creeks from invasive species such as Cherax destructors Provide critical food sources for aquatic life Environmental indicators or “canaries” as they are very sensitive to changes Help maintain river heath and structure What are the major threats to spiny crayfish? Illegal poaching devastates local populations for decades Water quality and environmental changes Predators – while the larger ones are apex predators the young are very vulnerable River bank degradation by wild pigs and humans etc. How can you contribute to the conservation of spiny crayfish? Enjoy, photograph and release any that you catch. Consider not to taking them and keep them in an aquarium Take your rubbish with you when camping Avoid eating them.  20 years to grow a legal size is difficult for them to recover from. All in all we are blessed here in Australia with the most diverse collection of different crayfish species which includes the largest and the smallest crayfishes in the world.  This is a heritage I would like my kids and their kids to enjoy.  Rob and I have been working towards this end for nearly a decade and we hope to be able to continue sharing our experiences with you. If you want to find out more and even contribute by coming along on one of our many expeditions please see the Australian Aquatic Biological website for more information and articles. Regards Paul…

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