By: Chris Hamerla
What is a Rusty Crayfish:
The rusty crayfish is a large, aggressive crayfish originally found in the Ohio River Basin of Ohio, Kentucky, Illinois, Indiana, and Tennessee. The rusty crayfish has spread through its use as bait in the fishing industry and to some extent through the aquarium industry. Anglers and aquarium owners should never release unwanted crayfish (or any plant, animal, or fish). In many cases these are illegal to release. Rusty crayfish mate once a year, typically towards late summer or fall. The young grow quicker than native crayfish. The easiest way to identify the rusty crayfish is by the two rust colored spots on each side of its body just behind the head. These rusty spots are visible even on different color phases of the crayfish. Rusty crayfish can survive in many conditions and habitats. Specimens have been found in marshes, ponds, lakes, and rivers with bottoms varying from rock to mud.
Why is the Rusty Crayfish Harmful:
Rusty Crayfish eat more than native crayfish. Their diet consist of plant and animal material. Rusty crayfish eat a lot of plants which contributes to large amounts of habitat loss for all living things in that body of water. Weed beds can be quickly cut down to barren open space. This loss of habitat can also decrease the amount of oxygen being produced for the lake. As the crayfish feed they clip off the plant and only eat a small amount. The remaining plant floats away and the crayfish move to another plant. Eurasian water milfoil, another invasive species, spreads easily through fragmenting and can be further spread by the rusty crayfish.
Not only do rusty crayfish consume a lot of food and habitat, but their aggressive nature causes problems with native crayfish. Areas usually inhabited by native crayfish are overtaken by the more aggressive rusty crayfish. Since the native crayfish are pushed out of their hiding spots and into the open they are more available to predators. In addition to being more available, these less aggressive, native crayfish are favored over the rusty as a food source by predatory fish. In some cases rusty crayfish will breed with native species which further lessens the numbers of native crayfish. Also, rusty crayfish can be a factor on fish populations as they feed on fish eggs.
How to control Rusty Crayfish:
Rusty crayfish have historically made their way to new bodies of water with the help of people. Through people releasing unwanted bait or planting the crayfish they have quickly and successfully expanded their native range. The best way to control their spread is to not transfer or release live specimens. In many states it is illegal to use crayfish as bait or to release them. In lakes that have rusty crayfish, trapping is the most popular and effective management tool.
Crayfish are popular pets but over time some people no longer want to take care of them. Find another person interested in keep it, but do not release it. This pertains to manmade ponds and water gardens too. Flooding can allow crayfish to escape and in some cases certain species of crayfish (the red swamp crayfish) have the ability to walk great distances across land to other water bodies. In many states it is illegal to release or introduce crayfish into these types of ponds.
Chris Hamerla is the Aquatic Invasive Species Coordinator of Lumberjack Resource, Conservation, & Development Council serving Lincoln, Langlade, and Forest Counties in northern Wisconsin. As the Aquatic Invasive Species Coordinator, Chris focuses on implementing AIS prevention and control efforts through public awareness and education programs. For more information or have any questions contact Chris at 715-362-3690 e-mail firstname.lastname@example.org
Learn more about each Aquatic Invasive Species (AIS) Click on the Links Below: