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BiologyReproduction is brought about by increases in day-length and in water temperature, with mating begins in the spring once the water temperature has risen above 15 °C. Females will spawn twice or more each season, producing up to 1000 eggs per spawning when fully grown. The male yabbie positions a spermatophore between the female's fourth and fifth pairs of walking legs, and the female breaks this open and fertilises her eggs with the contents. The small, green, oval eggs are then attached to the swimming legs where they take 19 – 40 days to hatch, depending on the water temperature (3). The hatchlings grow through three larval stages, moulting between each. Young yabbies moult every few days, pumping water under the new, soft shell to make room for growth. Once fully grown, the yabbies moult just once or twice a year. Freshly moulted crayfish are exhausted and vulnerable to predation due to the lack of protective covering (3). They may also loose legs during the moult - these are usually regenerated (2). The yabbie crayfish is omnivorous, feeding primarily on rotting vegetation, but is somewhat opportunistic, eating anything it comes across, including, on occasions, other yabbie crayfish. Cannibalism is not a normal state, however, occurring usually when there is insufficient natural food or when there are overcrowded conditions. They are nocturnal, being most active just after dusk and just before dawn. Predators include cormorants, herons, ibises, Murray cod, and Callop. Small, larval crayfish are also vulnerable to attack from other invertebrates (3).