Thermal Preferences and Distribution of Northern Michigan Crayfishes

Crayfishes function as both ecosystem engineers and keystone species, and they serve as the trophic linkage between benthic organisms and fish predators. Because crayfish behavior, physiology, and growth are controlled by temperature, thermal differences among habitats may have important implications for crayfishes and the ecosystems they inhabit. To investigate the association between crayfish and temperature, we measured thermal preferences of 3 crayfish species in lab experiments (2007), recorded summer water temperatures at 9 sites (July 1–August 9, 2008), and trapped crayfishes at these same sites in northern Michigan. Orconectes rusticus (non-indigenous) preferred nearly 1 °C warmer water (≈22 °C) than Orconectes virilis and Orconectes propinquus. Crayfishes inhabited sites with similar temperatures. These sites had average summer temperatures ranging from 21–23 °C. Sites without crayfish were on average 7 °C colder than sites with crayfish. Thus, crayfish thermal preferences were closely correlated with average summer water temperatures across aquatic habitats.