I'm going to say that what you have is a Signal Crayfish (leniusculus). They are found throughout the state in clean water rivers and streams. You are correct, they are very hardy. Too hardy in fact. They are originally from the Pacific Northwest. They have been exported internationally, as well as domestically. They are likely the reason the Sooty Crayfish is extinct, and the reason the Shasta Crayfish is endangered, as well as the reason the European Nobel cray is a species of concern (kind of an interesting story there, but I don't feel like writing it, do a little research on someones "good idea" to supplement Euro crays with Signals, if you want a good read). They make a nice tank addition. I am kind of surprised they can catch your cichlids. Mine got fairly beat up by convicts and jack dempsys. What water shed did you find this one in? Post a pick of the blue one, I would like to see that.