National Invasive Species Awareness Week: Rusty crayfish

Learn more about rusty crayfish, an aquatic invasive species in Michigan, and what you can do about it.

National Invasive Species Awareness Week: Rusty crayfish

National Invasive Species Week 2015 is February 22-28. Invasive species are plants, animals and other organisms that are not traditionally found in a given location (in this case the Great Lakes) and create a negative impact of some kind, whether ecological, economic, social and/or a public health threat.

To help celebrate, each day this week Michigan State University Extension is featuring a different aquatic invasive species that has invaded or has the potential to invade Michigan’s environment. Today’s featured aquatic invasive species is the rusty crayfish.

Species Name: Rusty crayfish (Orconectesrusticus)

Description: This aquatic invasive species is a crustacean with armored body segments similar in appearance to its larger saltwater relative the lobster. Rusty crayfish can reach 4 inches in length, have dark bands at the tips of their large claws and mature individuals often have rusty red spots on either side of the carapace.

Similar species: Northern Clearwater Crayfish (Orconectespropinquus). According to the National Oceanic and Atmospheric Administration (NOAA), a majority of individual rusty crayfish identified in Lake Michigan solely based on external appearance are actually hybrids of Northern Clearwater Crayfish and rusty crayfish.

Origin: Rusty crayfish are native to the Ohio River basin, including the states of Ohio and Kentucky.

How it came to the Great Lakes: The U.S. Department of Agriculture (USDA) credits DiDonato and Lodge 1993 with saying that rusty crayfish were probably introduced through bait bucket releases.

How long it has been here: USDA notes that rusty crayfish were first discovered outside of their native range in the 1960’s.

Extent of range: According to the U.S. Geological Survey (USGS), rusty crayfish has now been found in all of the Great Lakes except for Lake Ontario.

Why it is a problem: According to the Minnesota Sea Grant Program, rusty crayfish compete with native crayfish species and cause a decline in native species abundance, partially due to their aggressive nature causing them to displace native species from their hiding places and leaving them vulnerable to fish predation. They have also been shown to reduce aquatic plant abundance and species diversity.

How it is spread: According to the Minnesota Department of Natural Resources, the dumping of bait buckets and aquariums, as well as general commercial aquaculture activities are likely causes.

A cool/unusual fact: Rusty crayfish mate in captivity. Females can carry sperm with them so a single released female can potentially begin a new population if the environment is suitable.

Management actions/options: According to Minnesota Sea Grant, environmentally sound ways to eradicate introduced populations of rusty crayfish have not been developed, and none are likely in the near future. Preventing or slowing the spread of rusty crayfish into new waters is the best way to prevent the ecological problems they cause.

What you can do to help prevent the spread:

Like other invasive species, the best method of control is to prevent introduction. Practice the Clean, Drain and Dry method for watercraft prior to moving them between lakes.

Learn more about how you can help by visiting the Michigan Sea Grant website.

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