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Rusty crayfish live in lakes, ponds and streams, preferring areas with rocks, logs and other debris in water bodies with clay, silt, sand or rocky bottoms. They hide in the rocks but do not dig holes in it (Fig 2), which explains why they need permanent pools and lakes that are constantly supplied with water. They typically inhabit pools and fast moving streams of fresh, nutrient-rich water. (2)

Crayfish reproduce sexually. The female rusty crayfish mate with the male during the fall, but the eggs will be fertilized in the spring. The male's sperm is stored in the female until the eggs are ready to be fertilized. The eggs and the sperms are stored in the female and released at the same time in the water, where the sperms will fertilize the mature eggs. The eggs that are fertilized will attach to the bottom of the females tail., then the eggs will hatch in 3-6 weeks. The female can lay a large number of eggs up to 575 eggs. When the eggs hatched, the young's will stay close to the tail section for further protection. The eggs are attached to the abdomen in a large ball-like formation resembling a raspberry (Fig 3. Once the rusty crayfish become larger enough they can be on their own. The rusty crayfish can live from 3 to 4 years. (5)

SPECIFIC CHARACTERISTICS TO DISTINGUISH THE RUSTY CRAYFISH FROM ANY OTHER CRAYFISH

The rusty crayfish population have expanded in Wisconsin lakes and streams since their introduction in the 1960's . Investigators found out that there was no rusty crayfish in 1931. (1)
The first observation of rusty crayfish in Minnesota was in 1967 at Otter Creek in southern Minnesota. A statewide study reported that they have been found in 11 counties and 31 different lakes and streams. (1)

HOW WERE RUSTY CRAYFISH INTRODUCED TO WISCONSIN AND MINNESOTA ?

WISCONSIN

Rusty Crayfish were probably spread by non-resident people who bought them and used them as bait traps in fishing. As the number of rusty Crayfish increased, they were harvested for regional bait market and for biological supply companies.

MINNESOTA

In southern Minnesota and east central Minnesota the rusty crayfish was introduced to by natural dispersal of crayfish from Wisconsin. While in the rest of Minnesota it is though that non resident people brought them from states where they used rusty crayfish as bait traps and used them in Minnesota (1) .
Rusty crayfish are also sold to schools by biological supply houses. "Even though a warning not to release rusty crayfish into the wild accompanies crayfish sold to schools, such warnings may be forgotten, and rusty crayfish is released into the wild" (1). "In fact, this may have contributed to the spread of rusty crayfish in Wisconsin, according to Wisconsin Department of Natural Resources Fisheries Manager, Harland Carlson" (1).
It only takes one introduced female who has sperm stored to start a new population. Once a female is introduced into an area, rusty crayfish can spread via connected waters because the male’s sperm is stored in the female until the eggs are ready to be fertilized. Eggs and stored sperm are released at the same time and external fertilization takes place.

2) THE RUSTY CRAYFISH REDUCE THE NUMBER OF AQUATIC PLANTS AND INVERTEBRATES BECAUSE IT HAS A HIGH METABOLIC RATE (5)

2) Many chemicals have been used to kill crayfish. However, none selectively kill rusty crayfish without killing other native crayfish species.

4) Individuals should resist the urge to buy exotic pets, and make sure to never release non-native animals into the environment. People should dump any unused, live crayfish bait in the trash.

5) Benefiting from rusty crayfish: The rusty crayfish is large in size and can be harvested for human consumption as a good way of using the species. However, this will decrease the number of the adult population only. Once the rusty crayfish is introduced it is almost impossible to be eradicated.

8) If you think you've caught a rusty crayfish, freeze it or preserve it in alcohol and call the Invading Species Hotline at 1-800-563-7711.

TAXONOMIC HIERARCHY