Lately I've been studying crayfish. What a weird little creature they are if you take the time to really look and learn about them. Here's a bit of what I've learned...
Crayfish are part of the largest grouping of animals on earth called arthropods. Arthropods have hard exoskeletons and include insects, arachnids and crustaceans. Crayfish are crustaceans and differ from insects in that they breathe with gills and have two pairs of antennae. Crustaceans are also the yummy group and include stuff we love to eat like lobsters, crabs and shrimp. And well, crayfish. If you haven't ever eaten crayfish but like the other stuff on that list your missing out, they are delicious. And as every fisherman worth the name knows, the fish think they are delicious also. So here's more than you ever wanted to know about crayfish:
Back to those antennae, crawfish have a long pair and a short pair. The long whiplike pair help the crawdad keep track of what's going on ahead and behind it while the shorter stubby ones are for close in work. From everything I've read they are like a poor man's version of catfish whiskers in that they are sensitive to both touch and smell. Crayfish also have compound eyes on the ends of little stalks.
I'm not sure exactly how clear a crayfish sees it's world but compound eyes detect movement extremely well. The eyes mounted on stalks are called pedicles. If you watch a live crayfish, you can see the eyes move independently of each other. Instead of ears crawdads have thousands of tiny sensory bristles that can sense vibrations. The "brain" of a crayfish is just a mass of nerve ganglion just in front of and above the esophagus. I'm pretty sure most crayfish behavior is instinctive and they aren't exactly rocket scientists.
A crayfish has four pair of walking legs. The small appendages along the underside of the abdomen are the swimmerets. These help the gills circulate water through the body, so the crayfish can breath. And if you ever want to, you look at the first pair to determine the sex of a crayfish. (don't ask me, you might want to...) In boy crawdads, this first pair is used to deposit sperm into the oviducts of the female. They are larger and harder than the others. In girl crawfish, all the swimmerets are soft and used to carry the fertilized eggs and newly hatched young. Crayfish have 3 sets of tiny appendages around their mouth called maxillipeds. These appendages help the crayfish manipulate food.
All in all crayfish have 38 pair of appendages! Of course the ones we are all familiar with is that first pair with the big pincers on them. These are used to gather food and defend the crayfish from predators like fish. And don't think they don't use them to defend themselves, just let a big one you catch out of the river sometime latch on to you and you will change your tune. In fact studies have shown that smallmouth bass over and over again select crayfish with smaller claws if given choice. The old river rat trick of pinching the claws off crawdads you use for bait really does up you catch rate.
Along with claw size, studies show smallmouth bass select crayfish by body size also. The interesting part is that the biggest smallmouth bass, the trophy fish are the most selective by size. They consistently choose a crayfish about an inch and a quarter long if given a choice. I wonder if, given a smallmouth's long lifespan, that a ten or twelve year old bass has just learned by experience that those big craws can be bad news. Those big lobsters you sometimes see are shovelhead bait not bass bait unless the fish is really hungry. And even then the bass is going to suck that big craw in and blow it out several times trying to kill it, making it harder to hook on a bigger crayfish imitation too. If it's claws can't defend it, the crawfish's other option is to flee. This it will do by a sudden flip of its tail which will cause it to jet backwards a foot or so amazingly fast.
In the Midwest most crayfish mate in the fall. (don't ask me how, don't know, don't wanna know)
Then in spring the female will lay eggs which she glues to the swimmerets on her abdomen. These then hatch in 5 to 8 weeks into tiny crayfish which hang on another week or two before dropping off to fend for themselves. And along the way feed nearly everything in the river it seems. Everything from minnows like larger darters and chubs to dragonfly and hellgrammite larvae. There are some you tube videos of dragonfly nymphs eating little crayfish out there that are right out of a horror movie.
But crayfish are omnivores and get their revenge if they are lucky enough to grow up. Along with a bunch of vegetable matter they will chomp on pretty much anything that's small enough to kill with those pincers including things like small minnows. And as anyone who has went after crayfish with a minnow trap will tell you, dog food is a classic crawdad bait. Like I said an omnivore.
Crayfish undergo periodic moults, shedding the hard exoskeleton in order to grow larger, and then forming a new shell. During this time they are in fishing lingo, "soft craws" and extremely vulnerable to predators. And fish know this and moulting crayfish are just about the best live bait you can use. But don't discount using "hard craws" that are not moulting. Just remember what I said earlier about bigger bass preferring a small crayfish in the inch and a quarter range. Another interesting tidbit is that a crayfish can regenerate a claw if it loses it battling a fish or I dunno, a bigger crayfish. Over the course of two or three moults the claw will grow back. Which reminds me that when catching crabs in South Carolina it was illegal to keep the huge but somewhat rare stone crab. But you could keep one of the huge claws of this overgrown relative of the crawdad since it too would regenerate. (And one stone crab claw had more meat that a couple whole blue crabs.)
Speaking of eating crayfish, they aren't just for smallmouth. Besides smallmouth, channel and flathead catfish, walleye, saugeye, carp, trout, largemouth bass, freshwater drum and I'm sure a host of other fish eat crayfish. And of course people eat crayfish. My personal favorite way is grilled smothered in garlic butter and Cajun seasoning. But of course crayfish are famous as smallmouth food. And with good reason, a 12 inch smallmouth bass in late summer fills up to 70% of its diet with crayfish. Larger bass eat a lot of baitfish but they still eat a bunch of crayfish too. BTW don't ever, even on a drunken dare for a hundred bucks eat a live crawfish (or a raw dead one). A big percentage of crayfish are infected with a parasitic flatworm called a lungworm. After you scarf down the crawfish, the parasite comes out and burrows through the walls of the intestine, hoping to make it to the lungs where they can complete their life cycle and mature. Once in the lungs they form nodules that mature and grow. But sometimes they don't make it and get lost on the way to the lungs and they can end up in other organs, even in your brain. Yeah, YUK.
There are approximately 600 species in the world. Of those something like 350 live in North America. Which I'm guessing is more than the number of people who could tell them all apart.
Btw an Astacologist is someone who studies crayfish. And if you think the crawdads in grandpas pond are huge, the world's largest crayfish lives in Tasmania and can sometimes grow up to ten pounds! These giant crayfish can live up to 40 years too! Google Astacopsis gouldii, which is their latin name if you want to see some amazing photos. There are also colorless blind crayfish that have evolved to live in caves. According to ODNR there are twenty species of crayfish in Ohio.
If you keep crayfish for an extended period of time before using them as bait they will stay alive for a long time if you remember a couple things. First and foremost don't keep them in a bucket half filled with water unless it is aerated. But they don't need to be in aerated water if you keep them in something like a cooler with just a tiny bit of water in the bottom and something like grass that they can crawl up on. You see if they can keep their gills moist they can breathe air also. And try to keep the same size crayfish together, the big guys will definitely kill the little guys.