Early Detection of Invasive Species in Lake Superior
BY MICHELE WHEELER, ASHLAND FWCO
As the largest freshwater aquatic ecosystems on the planet, the Great Lakes are a treasured resource in the Midwest. More than 300 species of fish and other aquatic organisms inhabit the basin; however many of these species didn’t always call Great Lakes waters their home. Once established, these non-native invaders can substantially alter aquatic ecosystems and are difficult to control. Prevention and early detection are two of the tools agencies utilize most effective and efficient means to combat this growing threat.
Staff from the Ashland Fish and Wildlife Conservation Office (FWCO) has been working with federal, state, tribal, and local agencies including U.S. Environmental Protection Agency (EPA), Ontario Ministry of Natural Resources, Fond du Lac Band of Lake Superior Chippewa 1854 Treaty Authority, and Ashland County across the Lake Superior basin to monitor for new potential fish invaders. Sampling locations were prioritized based on likely introduction vectors, which included maritime commerce, recreational boating, and points of connectivity with the Mississippi basin. Between June and September 2013, the St. Louis River Estuary, Minnesota/Wisconsin (WI), Upper St. Marys River, Michigan/Ontario (ON), Thunder Bay, ON, and Chequamegon Bay, WI were sampled as part of a comprehensive early detection program focused on detecting new non-native fish species using a variety of sampling techniques that target a variety of life stages.
Larval fish sampling was conducted by EPA during June and early-July in the St Louis River Estuary. Ashland FWCO provided staff and a sampling vessel to assist EPA Mid-Continent Ecology Division. A total of 40 sites, less than two meters in depth, were sampled using a custom designed towing sled. At each site, the sled was pulled by hand for 100 meters for approximately three and a half minutes. The contents from the sled were then filtered through a fine mesh screen and preserved in alcohol. Over the next several months, the fish specimens will be identified to species and counted. The purpose of this research is to compare the efficiency of larval fish sampling to adult fish sampling for early detection monitoring.
Juvenile and adult fish sampling occurred with partner agencies at all four priority locations using fyke nets, boat electrofishing and bottom trawls. Sampling occurred during August through early-September to allow young-of -year fishes to grow large enough to be captured by our sampling gears. This past year was the first year of sampling with all three gear types in Chequamegon Bay, WI but the fourth consecutive year at the other three locations. This year’s fish samples are still being processed, but to date there have been no new detections of non-native fishes.
Environmental DNA (eDNA) monitoring was conducted over two days in August in the St. Louis River Estuary. Detection of species at low abundance or those that avoid traditional sampling gear can make early detection problematic. However, species leave traces of themselves as sloughed scales, mucus or fecal matter that can be detected in water using eDNA analysis. The Ashland FWCO sampled areas where eDNA was likely to accumulate in St. Louis River Estuary, including backwaters and near river mouths. A total of 100 water samples were collected and shuttled back to the Ashland FWCO lab for filtering. The samples were then shipped to the U.S. Fish and Wildlife Service’s Whitney Genetics Lab in La Crosse, WI for further processing.
Invasive species continue to threaten the diversity and stability of Great Lakes aquatic ecosystems. Once established, they can significantly alter the ecological stability of infested waters. Working cooperatively has proven to be an effective way to monitor for the arrival of any new invasive fishes. If a new species is detected soon after it is introduced, agencies can prepare control efforts that may be able to minimize the negative ecological effects an invasive species can have.