The theory is that after a big hailstorm a few years ago our dam filled with leaf matter and became a big food source for the small yabby colony in the neighbouring creek. They have since taken over the dam and multiplied . It is always muddy and has no frogs. Their scientific name is Cherax destructor due to their ability to damage dam walls, so we are trying to thin them out using a trap and allow more biodiversity such as frogs and other pond life to return. This big fellow is the biggest we have found - around 15cm.