Rob McCormack

This is a species of yabby found locally in the Great Lakes Region of NSW. Rumour has it that this species is quite widely distributed and can be found on the coastal regions from Newcastle to the Queensland boarder. The Cherax rotundus setosus means that they are of the genus Cherax which means smooth shelled. Rotundus refers to the rounded look of the yabby in the body and claws and setosus refers to the setae or hair that grows of the inside base of the claws. It is this hair (fur like) that makes it very distinct from other crayfish.

When I first started in the early 1980’s this was the species that naturally infested the property at Port Stephens and was one of the reasons we started commercial aquaculture. Everywhere we drove over the property and splashed through a puddle these local yabbies would be washed out. When we first started we did not know much about yabbies. I was just a recreational fisherman and aquatic enthusiast who had always just caught yabbies for food, bait for fishing and the fun of catching them. For the first few years as an aquaculturalist we stocked our ponds with both the local yabbies and Cherax destructors we captured out west. From this we learnt some interesting things about both species.

We constructed purpose built yabby ponds in the early days based on our experience of capturing yabbies from the wild. We had fished hundreds of dams, rivers and billabongs across NSW for yabbies and had a reasonably fair idea of the conditions in nature that yabbies thrived in and we tried to simulate those conditions in our ponds. When we stocked our first 20 purpose built ponds we found that things are not as obvious as we thought. In the purpose built yabby ponds if we stocked only local yabs they thrived. If we stocked the same type of ponds with only westerns they thrived too, but if we stocked both into a pond in a 50/50 mix then eventually the western yabs would grow faster and bigger and outbreed the locals to such an extent that after a few years only westerns were left in the pond.

The local yabbies thrive on the Eastern Drainage of the Great Divide in NSW. Yet we were unable to get the western yabby to establish viable populations in the natural habitat of the locals. Yet the locals thrived in the natural habitat of the western yabbies if no western yabbies were present.

The local yabbies have very specific habitat requirements, these can be categorised as follows. They need wet coastal conditions to thrive. They do not inhabit permanent water bodies only ephemeral watercourses or intermittent ponds or puddles. They are phenomenal burrowers creating a mass of interconnecting burrows. They thrive in the deep impervious clay beds. They are relatively placid and easy to handle compared to western yabbies.

These local yabbies have adapted to the habitat in which they can thrive and the most important constraint on their habitat and life expectancy is the eel. On the eastern drainage of NSW eels are the factor which determines the habitat of the local yabbies. All permanent natural water bodies on the eastern drainage are subject to infestation by eels. ( See eels in Further Information) Eels love eating yabbies and the Cherax species with a smooth shell can not protect themselves from eels. In a pond there is nowhere a yabby can go that an eel can not. In the wild these local yabbies can not survive in permanent water bodies due to the eels so they live in water bodies that dry up and then fill rapidly with water. They have extensive burrows deep into the ground where they survive when their water hole dries out and re-emerge when it rains and fills. These ephemeral watercourses, swamps, puddles and stump holes can hold massive populations of local yabbies. The trouble with the local yabbies is that they live in very crowded dirty conditions. They spend large amounts of their time in very unhygienic burrows and when the ponds/puddles these burrows are connected to fill they usually start drying up again right away so the water quality in them deteriorates. Local yabbies have very high infection rates of thelohania, mites, parasites and commensals.

The western yabbies prefer the permanent water bodies and do not like the ephemeral streams that continually dry up. Most western yabbies head for the bigger deeper more permanent ponds and are eaten by eels and do not survive on the coast in the wild. They only thrive in ponds designed to prohibit eels.

Local yabbies are usually green to brown in colour with an orange colouring in the joints. They do come in basically any colour including fluorescent blue. In the old days we did use to do selective breeding programs with the locals and it was extremely easy to breed a genetically blue variety for the aquarium trade which we did for many years before discontinuing it and only using the destructors.

We also use to produce a lot of these yabbies for the live bait industry as they are relatively placid compared the western yabs and were easier for the fishermen to get onto a hook without being attacked. However the demand for bait was so great that we had to swap back to destructors as they are just more prolific breeders.

Mostly these days we grow the locals for the research market. Back in the old days when we were growing locals and destructor together in the same ponds we use to notice offspring which had mixed traits of both species. We thought nothing of this as we had seen that the male destructors were a very horny animal always looking for a girl to have a good time with. Plus being bigger and stronger than the female rotundus setosus we just expected they were having their way with them wether they wanted it or not and these hybrids were the result of this behaviour. We thought nothing of it until two real crayfish experts, Bob Collins and Brad Mitchell from Warrnambool were up this way. It seems that two crayfish species should not breed together and even if they do they should not have offspring that survive. Brad was really intrigued with this unusual behaviour and did some studies on them and published a paper or two which created quite a stir in the academic community. Since then a mass of work has been done around Australia on this very unusual occurrence of 2 species interbreeding. WA Fisheries has done a lot of work on the hybrids which are all sterile males. They grow extremely fast due to hybrid vigour and because they can not breed are ideal for the live export market as overseas countries are not worried they will escape and establish populations in their rivers etc. The CSIRO in Armidale NSW has also done a lot of work on the hybrids but it is WA that has gone into the commercial production of hybrids. This creates a large demand for genetically pure stains of Cherax rotundus setosus for both Governmental and private hatcheries and this is what we supply.

Local yabbies do not grow very large in size. The large males seem to peak out at 80 gram and females at 60 gram, however the average adult population is in the 30 – 50 gram range. Females can berry up at a very small size usually from 10 gram up. Most berried females we capture are in the 10 – 30 gram range and do not seem to capture larger females with eggs for some reason. In this region the breeding season starts in mid to late August and continues into late February. Local yabbies are not always available so you must order them in advance.