Rusty crayfish
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| Rusty crayfish | ||||||||||||||||||||
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| Orconectes rusticus (Girard, 1852) |
The rusty crayfish (Orconectes rusticus), is a large, aggressive species of freshwater crayfish which is native to the U.S. states of Indiana, Kentucky, Ohio, and Tennessee. Its range is rapidly expanding in North America, displacing native crayfishes in the process [1]: it is known to have reached New England, Ontario, Illinois, Wisconsin, Michigan, Minnesota, Iowa, Missouri and New Mexico. The rusty crayfish was first captured in Illinois in 1973, and has been collected at over 20 locations in the northern portion of the state [2].
Rusty crayfish are considered a threat to many lake ecosystems. Once introduced, rusty crayfish proliferate quickly, often displacing native crayfish through hybridization and/or superior predatory defense. Predator defense in crayfish is primarily restricted to displays with their chelae, raising them in a threatening manner. Because rusty crayfish generally have larger claws and are more aggressive than congeneric species, several studies have noted that fish predators actually avoid consuming rusty crayfish in favor of more docile or smaller species.
Ecosystem impacts of rusty crayfish are often profound. Rusty crayfish remove aquatic plants, either through consumption or by clipping the plant at its base. Researchers have theorized that this ability to decimate aquatic plants actually leads to further population expansion by eliminating key habitat for the juveniles of sunfish species that act as predators on juvenile crayfish.
[edit] External links
- ^ Jeffrey Gunderson (2006-01-23). Rusty crayfish: a nasty invader: biology, identification, and impacts. Minnesota Sea Grant.
- ^ C. Taylor. Exotic crayfish. Illinois Natural History Survey.
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Diet: Submerged plants, detritus, other crayfish, juvenile fish, sunfish, fish eggs, macrophytes.
Submissive fish species such as the sunfish can not defend their nests from rusty invasions and so lose their future offspring, greatly reducing the fish population. Other species of fish such as bass are more aggressive and will eat any invaders that wander too near to their nests, or if the intruder is too big to eat, it will simply pick it up and move it out of its territory.
