Red Swamp Crayfish Procambarus_clarkii credit Mike Murphy

Red Swamp Crayfish, Photo: Mike Murphy

The remains of invasive crayfish were found at a popular fishing site on Lake Macatawa

Native crayfish don’t get much attention in the world of aquatic science. In fact, the last comprehensive survey of crayfish in Michigan waters was conducted in 1975. The underwater world has changed a lot since then, in large part due to the arrival of invasive species like the rusty crayfish. Dr. Brian Roth with Michigan State University’s Department of Fisheries and Wildlife is leading a project in collaboration with the Michigan DNR-Fisheries Division that will map the current distribution of both native and invasive crayfish species.

In addition to the mapping component, Dr. Roth and graduate student Kelley Smith are also working on a risk assessment for another invader that has never been found alive in Michigan waters. The red swamp crayfish is an incredibly hardy and destructive pest that also happens to taste great. Although the red swamp crayfish is native to the southern U.S., invasive populations have invaded coldwater streams in Germany and would likely flourish in many habitats in the Great Lakes region.

A sampling crew led by Smith was working on Lake Macatawa in Holland, Michigan, last month when the two components of the crayfish project came together. While taking a break from crayfish trapping, Smith decided to walk along a boardwalk and look for evidence of red swamp crayfish.

Two years ago, conservation officers with Michigan Department of Natural Resources noticed some anglers on Lake Macatawa and the lower Grand River were using red swamp crayfish as bait. In 2013, it was illegal to transport live crayfish into Michigan for use as bait, but loopholes remained.

crayfishposterThe red swamp crayfish is widely available from southern fish farms and they are sold alive by food markets, pet stores, and biological suppliers. Anglers had evidently been buying crayfish intended for food or other uses, and then using them as bait. State law was changed in 2014 to prohibit possession of live red swamp crayfish, regardless of intended use.

Unfortunately, they are still being used as bait. Smith found the remains of several dead red swamp crayfish at Kollen Park in Holland on June 26, 2015. Although it is possible that anglers had purchased dead crayfish, it is also possible that they were purchased alive. Both the MSU crew and Michigan Department of Natural Resources conducted additional sampling in Lake Macatawa and the lower Grand River in response to the finding. To date, no live red swamp crayfish have been captured.

This is a good thing, because the red swamp crayfish is nearly impossible to get rid of once they establish breeding populations. They are able to move over land and construct burrows where they can evade even the most aggressive aquatic chemical controls. In fact, they are so hardy that they can survive in some wastewater treatment facilities after being flushed down the toilet.

To protect Michigan waters from the red swamp crayfish and other invaders, Michigan State University Extension recommends contacting a pet retailer or veterinarian regarding proper euthanasia and disposal of unwanted pets. Unwanted aquarium plants should be placed in sealed plastic bags before disposing in the trash. Unused live bait should also be disposed in the trash and never released into the wild. Report red swamp crayfish sightings and send photos to the DNR-Fisheries Division’s Aquatic Invasive Species Coordinator (Seth Herbst, or by using the Midwest Invasive Species Information Network (MISIN). If you find live red swamp crayfish being offered for sale in Michigan, contact the DNR’s Report All Poaching hotline (800) 292-7800.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.