Biology of the Northern Crayfish Description Crayfish, of which our own Northern Crayfish (Orconectes virilis) is one of about 500 species worldwide, are crustaceans related to copepods, barnacles, crabs, shrimps, lobsters, etc. (Class: Crustacea, Order: Decapoda, Family: Cambaridae, Genus: Orconectes, Species: virilis) The Northern Crayfish grows to a length of about 10-12 cm, not including the 2 pairs of long antennae or the large chelipeds, the large claw or pincer bearing legs, that extend forward. The chelipeds often have a bluish tint, particularly in the males which have larger chelipeds and larger pincers than females. The head and thorax are covered by a shell-like carapace, usually brownish to rusty red in colour. There are four pairs of jointed walking legs called pereopods also attached to the thorax. (The chelipeds are actually modified pereopods.) The jointed abdomen, which can be folded under the thorax, has 5 pairs of small limbs called pleopods, or swimmerets. The first two pleopods of males are modified to aid in sperm transfer. In female crayfish the first two pleopods look the same as all the rest. In crayfish the pleopods beat to maintain a current of water over the feather-like gills which are located along the sides of the thorax beneath the carapace. At the end of the abdomen is the telson, which together with the paddle-shaped uropods forms a flipper-like tail. A crayfish normally walks forward on its pereopods, but when frightened it flips its tail rapidly and repeatedly under its thorax and scoots away backwards. More than 1 crayfish? I guess the plural of crayfish is crayfish, and as for fish, when you talk about more than one species it would be crayfishes?  Distribution Here's a map of our best guess of the range of the northern crayfish in Manitoba (adapted from The Handbook of Crayfish of Ontario). They certainly occur throughout southern Manitoba, but how far north they range isn't known. (Anybody up north know? Drop us a line at nnz@naturenorth.com.) Crayfish Update (Fall 1998): Since this article was first published (you may remember, we originally stated that the northern crayfish was the only crayfish to occur here), it has come to our attention that another species of crayfish, Orconectes immunis, the papershell crayfish is also known to occur in Manitoba. Fred Shueler, Curator, Eastern Ontario Biodiversity Museum, Grenville Co., Ontario, informed NNZ that large numbers of specimens of this species, collected in the region of Brunkild, MB, were forwarded to the Canadian Museum of Nature from 1973 - 1985. And we passed on this information to the Manitoba Museum of Man and Nature. Crayfish Update (March 2008): Sadly, since this article was first prepared the rusty crayfish, Orconectes rusticus, an introduced species, has been found in Manitoba. It is apparently well established in Falcon Lake in the Whiteshell Provincial Park. It is an aggressive invasive species and tends to displace the native northern crayfish. Unfortunately, identifying crayfish can be a bit tricky. The best resource I was able to find for species identification and for general information on crayfish is The Handbook of Crayfish of Ontario (by D.W. Crocker & D.W. Barr, 1968, Published by University of Toronto Press), but this book is only available at a few technical libraries. PLEASE DON'T USE CRAYFISH AS BAIT! You may unknowingly aid the spread of the rusty crayfish. Apparently it is now illegal to even possess crayfish in Manitoba. Seems like a little over-the-top response to the Rusty Crayfish situation, but they're the government. Read their position: Manitoba Conservation Rusty Crayfish page. .  Habitat Crayfish habitat in a small urban creek Where do they live? Crayfish probably inhabit all aquatic environments in Manitoba, except marine. They can be found in lakes, rivers, streams, marshes and ponds. Wherever there is a permanent body of water that is deep enough not to freeze solid or experience winter die-off from oxygen depletion, you may find crayfish. The one habitat requirement that the northern crayfish seems to have is the need for shelter in the form of rocks, logs or thick vegetation in which to hide from predators during the day time.  Food Northern Crayfish probably eat all kinds of things. All "the books" suggest crayfish eat some aquatic plants as well as invertebrates, such as snails and insects, and tadpoles and small fish. They are probably best described as "opportunistic omnivores", they eat whatever they can get!. While they can catch some quick moving prey like tadpoles or fish, they probably get a lot of their food by scavenging dead animals. My captive crayfish love to eat dead fish (Hey, nothing goes to waste in my aquariums!), and I've seen them grab the odd live one, too. Crayfish feeding  Crayfish As Food What eats crayfish? Fish are probably the main consumers of crayfish. What fisherman (or am I supposed to say fisher person now?) doesn't have a rubber crayfish lure in his (or her) tackle box? But turtles, raccoons, mink, herons, cranes and lots of other critters will chow down on crayfish when they can catch them. Crayfish are an important part of the aquatic food chain. They are also an important part of the human food chain! Well, not so much in these parts, (Though you'd eat a lobster, right?) but in many parts of the world crayfish are a delicacy. Remember how Jed, Ellie-May, Grannie and especially Jethro would smack their lips at the thought of a big pot of crawdad gumbo? (Crawdad or crawfish are other names for crayfish.) Crayfish are a big-time food item in the United States and, increasingly, in Europe. Close to 45 million kilograms (100 million pounds) of crayfish are harvested annually in the U.S., with most of this coming from aquaculture operations in Louisiana. Crawfish, as they are known there, are important ingredients in Cajun cooking. Crayfish production in Louisiana is the second largest aquacultural industry in the United States. Reproduction Crayfish can mate in autumn or in spring. However, the eggs are not fertilized and laid until the spring. The females can store the sperm from a fall mating. And they protect their eggs by carrying them around under their tales. The eggs are stuck to the swimmerets in a large ball resembling a raspberry. In fact, the females are said to be "in berry" while they are carrying their egg masses. The eggs are laid from late May to early June and hatch by July. The young hatchlings look just like miniature adults, and can probably grow to be about 2-3 cm long by the fall. Crayfish don't live very long. The males usually die after mating when they are about 2 years old. The females die after their young hatch, also at about 2 years of age. Crayfish occasionally live longer, but it's thought that none survive beyond their 4th spring. Young crayfish in hand Habits Crayfish are most active at night. They leave the protection of the rocks or other cover to forage in the dark, no doubt aided by their long, sensitive antennae. They can even crawl up onto land next to water to go from pool to pool in search of food or to forage along the shore. The location of their gills under the carapace means that they stay moist for some time even when the crayfish is out of the water. This and the crayfish's ability to tolerate low oxygen levels allows them to venture from the water for short periods. If encountered on land by a predator, or a pesky photographer, they adopt a defensive stance with claws at the ready. Crayfish in defensive stance Regular crayfish activity is interrupted periodically for moulting. Like all arthropods (animals with a hard exoskeleton and jointed legs: crustaceans, insects, arachnids, etc.) they must shed their hard shell-like skin in order to grow. For several days after moulting, crayfish stay in seclusion until their new skin hardens enough to protect them from predators. What do crayfish do in winter? It's thought that they become much less active, but they do not go dormant or hibernate. Adult crayfish move to deeper water for the winter to avoid possible freeze-outs. The End Acknowledgments Some of the information in this article was drawn from the following sources or individuals: The Handbook of Crayfish of Ontario. By D.W. Crocker & D.W. Barr. 1968. Published by University of Toronto Press Dr. Premek Hamr, (Freelance Crayfishman) 540 Lakeshore Rd. Oakville Ont., L6K3P1 Fred Schueler, Eastern Ontario Biodiversity Museum Grenville Co, Ontario, Canada (RR#2 Oxford Station, K0G 1T0)