Distribution of crayfish in the Southern Basin of Lake Michigan and the Greater Chicago Region

Crayfish represent important links in aquatic food webs because they have diverse, omnivorous diets and are an important source of energy for fishes and birds. Crayfish have the ability to increase sediment transport through bioturbation, some are considered ecosystem engineers due to their burrowing habits, and crayfish invasions have been linked to large declines in biodiversity and changes in ecosystem structure and function. Despite their ecological importance and the threats that invasive crayfishes pose, the distribution of crayfishes in the Laurentian Great Lakes is not well studied. Here, we report on four years of intensive crayfish surveys in the southwestern portion of the Lake Michigan Basin, a region with diverse freshwater ecosystems and few previous records of crayfish distribution. From 2015 to 2018, baited minnow traps and SCUBA were used to document the distribution and abundance of crayfish across streams, rivers, inland lakes, and Lake Michigan. Six species of crayfish were captured, including two invasive species. The invaders are the widely distributed and abundant Faxonius rusticus (rusty crayfish) and Procambarus clarkii (red Swamp crayfish), a species early in the invasion phase. Native species were found in fewer habitat types and were less abundant than invasive F. rusticus. Comparing our results to previous sampling showed that native crayfish distribution and diversity have declined at the same time that F. rusticus has spread over recent decades. There is potential for new and recently introduced invaders, such as the red swamp crayfish, to further alter ecosystems.