DISTRIBUTION OF NATIVE AND INTRODUCED CRAYFISH IN MAINE: AN ONGOING EFFORT TO DEVELOP BASELINE DATA BEFORE NEW SPECIES INVADE

Invasive crayfish are an increasing problem in North America, and can threaten freshwater resources through consumption of aquatic insects, snails, plants and fish eggs, or by displacing native crayfish species. Based on past research, Maine's low crayfish diversity along with little habitat overlap could lead to vulnerability with non-native invasions. Detecting crayfish invasions is difficult unless there is reasonable knowledge on native distributions. This project's goals are to identify and update distributions of native and non-native crayfish in Maine and identify crayfish “hot spots” that may indicate an invasion. Crayfish samples were collected as part of the Department of Inland Fisheries and Wildlife's brook trout stream surveys in 2007 and 2008 and by University of Southern Maine in western Maine in summer of 2008. In some cases we revisited sites sampled previously by other researchers to confirm the presence of invasive crayfish. The presence of crayfish was assessed in 1061 stream sites (MeDIFW) and 13 other locations checked by USM. We found O. virilis a native species to be most common at 94% of the total catch, followed by O. limosus (5.0%) and O immunis (1.0 %). Non-native crayfish are suspected in select locations throughout the State by human introductions including bait buckets and harvesting attempts. This is an ongoing effort that depends in part on tips from lake shore owners, anglers, and other outdoor enthusiasts.