Learning to Be Vigilant

Updated: Feb 5

The following article was written by Larissa Cassano-Hamilton, Watershed Specialist with the Mercer County Conservation District and was originally included in the Summer/Fall 2020 edition of the "Tracking Invasive Species with Pennsylvania iMapInvasives" newsletter.


Eurasian water-milfoil. Credit: Alison Fox, University of Florida, Bugwood.org (link)



In northwestern Pennsylvania, we are lucky to be surrounded by so much green (and blue) space - from farm fields, to game lands, to state parks with lakes and rivers. These great spots get more and more visitors that come and go throughout the season, especially now during the COVID-19 pandemic with outdoor recreation on the rise in the United States. However, sometimes visitors might accidentally take home more than just good memories and a nice-looking fish after visiting their local park or recreational area.


Aquatic invasive species (AIS) are plants and animals that can get stuck on gear and vessels and be easily introduced into other bodies of water via movement by humans or waterfowl. AIS can accidentally be transported on boats, pets, and recreational gear, and it's important for outdoor enthusiasts to be vigilant and check for aquatic hitchhikers whenever they are recreating on a waterbody. It's also recommended to take note of posted signs that display information about aquatic hitchhikers.


One species in particular, Eurasian water-milfoil (Myriophyllum spicatum), is an invasive aquatic plant that boaters and fishermen should be checking their gear for. Because it can spread via fragmentation, a single piece of this plant can begin a new population if transported to a new location.


Eurasian water-milfoil is a feathery, submerged aquatic plant that can quickly form mats in shallow areas of lakes and rivers in North America. These mats can then interfere with swimming and entangle propellers, which hinders boating, fishing, and waterfowl hunting. Heavy infestations may even reduce property values. Dense milfoil infestations can displace native aquatic plants, which negatively impacts fish and wildlife.


Eurasian water-milfoil line drawing. Credit: Minnesota Sea Grant