Grew up in Australia catching crays (or Yabbies as we call them). As a kid we used to catch them with a piece of stew meat on a string, pulling in slowly and using a colander behind them when they saw us a would let go and try swim away. They are in the dugout systems over there and rivers as well, we used to use traps and drag nets to catch them. Have caught so many we filled a 4 x 8 trailer lined with a tarp, varying in size from 3 inch to 15 inch. Here's pics if you don't believe
http://www.crayfishworld.com/yabbykidscatching.htm
We've even caught females so big you can eat the roe off of them!!