Rusty crayfish

The rusty crayfish is an invasive species of crayfish scientifically known as Orconectes rusticus. Rusty crayfish possess claws that are larger than many other species in areas they have invaded, and will choose fight over flight if threatened. Due to these traits and actions they are less likely to be eaten by predators and can therefore populate and continue their destruction of habitats. These crayfish impact new environments dramatically, particularly through their tendency to destroy underwater plant beds that house fish and other native underwater creatures. This destruction impacts environmental as well as economic situations in some infested areas. By diminishing local fish populations they deplete resources for commercial fisheries in the area. Several methods of control have been found including spurring the growth of predator populations and trapping adult crayfish. Preventing the spread of these destructive creatures is difficult, as the female crayfish can store sperm until she is ready to fertilize her eggs. Therefore, one female with stored sperm is enough to start an entirely new population in any suitable habitat. To stop the infestation, the entire population must be removed, which can prove to be a nearly impossible task.

Body Design
The rusty crayfish has a brown body and claws that are bigger than native crayfish claws. Its claws have grayish-green to reddish-brown color with dark black bands on the tips. Two rusty patches are located on the sides of the abdomen. It looks like it was picked up with hands that were painted. Due to hybridization of the male rusty crayfish with the female rusty crayfish, their rusty spots might not always be visible or even present. Their mouths are smooth instead of the native saw-like mouth. The patches may be less visible on different places of the body. The ‘S’ shaped claws have an oval shaped gap while closed. Males are usually larger than females.

They can be differentiated apart from native crayfish because of their black tipped claws and the rusty spots on their back. They can range from two to eight inches. The rusty crayfish can be identified in several ways: they usually have rust colored spots on their sides just above their abdomen; hence the name rusty crayfish and their claws are usually smoother and more robust compared to the native species. Their claws are approximately five inches long, their legs extend for about two inches, and the end of their body is about three and a half inches long. Males are typically longer than females when they mature and both females and males have bigger, meatier claws than most native crayfish.

Life Cycle
Orconectes rusticus (Rusty Crayfish) have a relatively long life cycle as compared with other arthropods. . They typically live about three to four years, reaching maturity after one year, in which time they have grown from eggs into juveniles and then into young adults. During one of the mating seasons, which span from late summer to early fall and in early spring, adult crayfish copulate, leaving the sperm inside of the female until fertilization is ready to occur. When it does, hundreds of fertilized eggs remain inside of the female for about three to six weeks, but cling to the female after hatching until they are capable of surviving on their own. This may take several weeks, as juvenile crayfish are quite defenseless against predators. .

Juvenile crayfish undergo eight to ten molts over the course of the first year of life in order to become adults. A molt basically consists of the crayfish outgrowing its old shell and a prepared new shell taking the place of the one that falls off. Having been on their own for several months, the juvenile crayfish will have found its own habitat and niche within its ecosystem and will only undergo very gradual changes to become adults at a length of one and three-eighths inches. Some crayfish may eventually reach up to four inches in length, but most will not grow much longer than two to three inches. Eventually the adult crayfish will complete the life cycle by breeding, caring for the young, and dying. .

Ecology
The Orconectes rusticus (rusty crayfish) is native to Ohio, Kentucky, and the Ohio River basin. It has invaded many lakes and streams in Minnesota, Wisconsin, Michigan, Illinois, Ontario, and parts of 17 more states (see image). Orconectes rusticus only live in freshwater biomes. Orconectes rusticus are opportunistic feeders. They eat a variety of aquatic plants, benthic invertebrates (like aquatic worms, snails, leeches, clams, aquatic insects, and crustaceans like side-swimmers and waterfleas), detritus (rotting plants and animals, including associated bacteria and fungi), fish eggs, and small fish. Young crayfish only feed on benthic invertebrates like mayflies, stoneflies, midges, and side-swimmers.

Orconectes rusticus can cause different negative environmental impacts. Orconectes rusticus is aggressive and often displaces native or existing crayfish species. Displacement of crayfish, such as Orconectes virilis and Orconectes propinquus has occurred in many northern Wisconsin lakes, northern Ontario, in the Kawartha Lakes region of southern Ontario, and in Ohio, Orconectes sanbornii has been displaced. The most serious impact, however, is the destruction of aquatic plant best. This can be most damaging in lakes where beds of aquatic plants are not abundant. Rusty crayfish also can harm fish populations if they eat fish eggs. A way to control Orconectes rusticus is to restore natural predators like bass and sunfish populations.

Spread and Management
Because of the extreme impact Orconectes rusticus can have on non-native environments, preventing the spread of the rusty crayfish and reducing existing invasive populations has become a concern to citizens and government agencies in invaded areas. Doug Jensen, Sea Grant Exotic Species Information Center Coordinator, states, “Once rusty crayfish gain a foothold there is no environmentally-friendly way to eradicate them. Preventing the spread of rusty crayfish. . . is an essential part of protecting our inland waters.” Jensen is a strong advocate for education regarding this invasive species. He believes that if people know more about it, its spread can be prevented. By transporting or releasing the crayfish to new waters, or even by transporting aquatic plants or water, the rusty crayfish can be spread to new areas. The harvest of these crayfish for bait, food, or biological supply companies aids in the spread of these invasive creatures. Using crayfish as live bait has even been made illegal in the state of Minnesota for these reasons. Other areas prohibit any possession of these crayfish to reduce its spread, while some allow its use for certain purposes but do not allow it to be released into the environment.

There are several methods of varying effectiveness to remove or diminish rusty crayfish populations. While there are chemicals that can kill only crayfish none have been found that specifically kill the rusty crayfish species. A three year experiment was conducted in an isolated lake in Wisconsin to test methods of removing or reducing the rusty crayfish population. The researchers found that the rusty crayfish population could be controlled through heavy trapping of the crayfish and also by increasing the native fish populations. The fish populations were allowed to increase by controlled fishing and this increase had a significant impact on the crayfish numbers. While the predatory fish reduced the crayfish numbers the most, trapping removed the adult crayfish with high reproductive potential, restricting continued growth of the species. The researchers suggest that a combination of the two methods merits more research and is effective.

WDS - Rusty CrayFish of the Mississippi River
Number 1 Wildlife Documentary Series of Amazing Wildlife in Minnesota. This video is great for 3D Animators to do a walk cycle animation. Use this footage as a background in 3DS Max, etc. WAgNXFeGxQw