Why Is The Rusty Crayfish Considered To Be A Bad Actor?
What makes the rusty crayfish so special? After all, there are quite a large number of crayfish species scattered throughout the world. In the United States these aquatic animals are called crayfish in some places, crawfish in other places, and crawdads in still other places. In a few locations the crayfish is called a mudbug, probably the least appetizing of the various names. To many people, there are few things more enjoyable than to sit down to a meal of crayfish, or crawfish, cooked New Orleans' style.
A Very Invasive Species - The rusty crayfish is good eating too, though it is not famous for that reason. This native of the freshwater streams and ponds of the Ohio River Valley has gained fame for two reasons. Number one, it is noted for having a bad temper, and number two, it is extremely invasive.
One would normally think an invasion of crayfish would be a good thing, that is if you like to eat them, or if you wish to use them as bait when fishing. The problem is, the rusty crayfish are displacing other crayfish species, species which are also good eating, as well as destroying aquatic plant beds that many fish and other water creatures need to survive. In other words, this species of crayfish doesn't simply spread, it tends to take over. The problem is particularly severe in lakes located along the northern tier of states, as the water temperatures in the region tend to keep aquatic plant beds smaller and fewer in number than elsewhere.
Crayfish resemble small lobsters, which isn't surprising since they are related to the lobster. The crayfish we are familiar with are all fresh water creatures. They don't live in salt water, as do lobsters. A rusty crayfish will typically grow to a length of about 4 inches. This is not terribly large as crayfish go, but the claws of this species are somewhat on the large size, and they can deliver a painful pinch. Wading in a pond where these fellow live can be an adventure, as they are just as apt to attack as they are to scurry away, with a pinched toe being the result. Australia is home to some very large crawfish species, each weighing several pounds, and there are 7 different species found in Europe. The crayfish kingdom, if there is such a thing, would have be in the southeastern United States, where approximately 330 different species compete for whatever food is available. Crayfish are largely scavengers, but they also eat small fish and other aquatic creatures.
Fishermen Are Mostly Responsible For The Invasion - It is their use as fishing bait that is thought to be largely responsible for the spread of this species into areas where it had never before existed. Crayfish are often used as life bait, and a certain percentage will either manage to get free, or are simply thrown away at the end of a day of fishing. A single female can lay the groundwork for populating an entire lake. The reason for this is that after a male has fertilized the eggs, the female will carry them inside of her for some time, and may end up depositing them in a lake she has been transported to by a fisherman.
The rusty crayfish was first introduced into Wisconsin in the 1960's. By 1970 they populated roughly 3% of Wisconsin's lakes and streams. By 2009 this had grown to 50%. Similarly, in Minnesota, the crayfish population has grown from several found in a single creek in 1967, to a much greater number found in around 50 different lakes and streams today.
The Best Solution? Eat Them - At the present time, there are not any programs in place designed to reduce rusty crayfish populations in the states most affected. Laws have been passed that forbid the introduction of these crayfish into any waters, and residents have been encouraged not to release any that are being kept as science projects or as pets. The species is commercially harvested for both bait and food, and there seems to be some movement towards promoting this species of crayfish as a delicacy, which it is, and encouraging more people to acquaint themselves with the delicious taste.
Part of the problem this species causes is not simply its introduction in large numbers to a lake or stream, but the fact that the rusty crawfish has a high metabolic rate, and therefore is a relatively voracious feeder, often leaving the equivalent of table scraps for the other denizens of a given lake or stream. It is hard for anyone who loves to eat crayfish to think badly of them, but this particular species has turned out to be a bad citizen wherever it has been introduced. The saving grace may lie in its great taste, especially when it is prepared Cajun style. There is a flip side however. As more and more people find out how good these crayfish taste, they may be tempted to want them introduced in even greater numbers.