The basic precondition for keeping any animal in captivity is the exact knowledge of the species and its requirements. Unfortunately, careless mistakes happen, and some crustacean species are often mistaken for each other in trade, sometimes as early as at the importer’s or wholesaler’s, and then bad information gets passed down to the customer. Free One-Day Delivery on millions of items with Prime. Low prices across earth's biggest selection of books, music, DVDs, electronics, computers, software, apparel & accessories, shoes, jewelry, tools & hardware, housewares, furniture, sporting goods, beauty & personal care, groceries & just about anything else. Means of Introduction: Human activity best explains the presence of the rusty crayfish in areas outside of its native range. Angler bait bucket emptying is thought to be the primary cause of introduction and species spread (Berrill 1978, Crocker 1979, Butler and Stein 1985, Lodge et al. 1986, Hobbs et at. 1989, Lodge et al. 1994, Kerr et al. 2005; Kilian et al. 2012). This Crayfish Worksheet is suitable for 3rd - 5th Grade. In this crayfish worksheet , students examine a labeled diagram of a crayfish and then answer 8 fill in the blank questions about crayfish after doing further research. Really, any substrate is fine. I use pool filter sand, and my cray loves to dig out his own hidey-holes under rocks, this is pretty typical behavior, so I'd avoid using two different fine substrates unless you're ok with them getting mixed. Finer gravel and sand are probably ideal if you want to see burrowing behavior.