Crayfish

Crayfish are one of the most threatened groups of animals in the world.  About 45 percent of North American crayfish species are considered to be at risk of extinction. However, a few crayfish species are among the world's most invasive freshwater organisms. Taking into consideration that invasive crayfish are the leading cause of decline in native crayfish populations, it seems that crayfish's greatest threat is other crayfish.

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