State of Montana Website Montana State Parks Website
Crustaceans
ANS—Crustaceans

Rusty Crayfish


Description

  • Orconectes rusticus
  • Spreads via bait buckets, ballast water, and aquarium dumping
  • Females can carry fertilized eggs, one female can start a new population
  • Native crayfish populations have been eliminated by the rusty crayfish through competition and disease
  • Common aquarium crayfish
 
Rusty Crayfish. Rusty Crayfish

General Characteristics

  • Larger, black-tipped claws
  • Rusty spots on carapace
  • Adults 2-8" long

Links

US Geological Survey (USGS)—Rusty Crayfish

 

Spiny Waterflea


Description

  • Bythotrephes cederstroemi
  • Small crustacean with a long, barbed tail spine
  • Native to Europe
  • Introduced into the Great Lakes in 1980’s via ballast water
  • Spreads by overland transport of resting eggs on fishing gear, in bilge water, livewells and bait buckets
  • Competes with juvenile fish for food

General Characteristics

  • 3/8" long
  • translucent color
  • bulbous egg pouch
  • straight caudal appendage
  • look like gelatinous-like blobs on downrigger cables