In honor of it being National Invasive Species Awareness Week, our Watershed Word of the Week is Invasive Species.  An invasive species is any plant or animal species that was introduced to an area that it is not native to.  These species tend to disrupt and adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically.

In our area, one of the most common and recognized invaders is Eurasian Water-Milfoil.  Milfoil is thought to have been introduced in the 1940’s and is now present in every state in the United States.

Invasive species are extremely good at taking over an area for several reasons.  1. They reproduce quickly. 2. They have no natural predators. 3. They grow rapidly and displace native species.  With just these three advantages, it is no wonder when an invasive species is introduced, they take over and are extremely difficult to remove.

Invasive Species in Maine (Maine Invasive Species Network, University of Maine):


Common Name Species Name Source
European Fire Ant Myrmica rubra Univ of Maine / Maine NAP
Gypsy Moth Lymantria dispar GMRI – Vital Signs
Spotted Wing Drosophilia Drosophilia suzukii Univ of Maine
Forest Pests including Emerald Ash Borer, Asian Longhorn Beetle, Hemlock Wooly Adelgid, Elongate Hemlock Scale, Brown Spruce Longhorn Beetle, Winter Moth, European Wood Wasp Agrilus planipennis, Anoplophora glabripennis, Adelges tsugae, Fiorinia externa, Tetropium fuscum, Operophtera brumata and Sirex noctilio Maine Forest Service

The Maine Forest Service wants to know about any of the species of forest pests listed above. Contact them at (207) 287-2431 or 1-800-367-0223 (in State).

Not sure what you have? Visit UMaine Cooperative Extension – Homeowner IPM Pest ID Page or the Insect and Plant Disease Diagnostic Lab.

Marine Invaders

Common Name Species Name Source
Asian Shore Crab Hemigrapsus sanguineus Maine Dept of Marine Res
Dead Man’s Fingers Codium fragile GMRI – Vital Signs
Lacy Crust Bryozoan Membranipora membranacea GMRI – Vital Signs
Green Crab Carcinus maenas GMRI – Vital Signs
Hairy-clawed shore crab Hemigrapsus penicillatus GMRI – Vital Signs
Chinese Mitten Crab Eriocheir sinensis GMRI – Vital Signs
Common Periwinkle Littorina littorea GMRI – Vital Signs
Rapa whelk Rapana venosa GMRI – Vital Signs

If you see Asian Shore Crab, contact Peter Thayer (Maine Dept of Marine Resources) via email at  pete.thayer@maine.govwith the date, location, and number of crabs you have seen

Fish Introductions

Common Name Species Name Source
Northern Pike Esox lucius Maine Dept of Inland Fisheries

The illegal introduction of any fish into any Maine water is a Class E crime, punishable by fines. If you know of an illegal introduction, protect Maine’s fisheries and call Operation Game Thief at 1-800-253-7887 or visit the MDIFW website for more information. A list of “unrestricted” fish and wildlife species are listed by the Dept of Inland Fisheries and Wildlife for possession and sale.

  •  If you know of a good resource not currently included here please contact Caleb Slemmons ( to add a link.

Terrestrial and Aquatic Plants Identification Page.

Invasive Species of New Hampshire

If you think you have identified an invasive species please call the proper authorities to manage and deal with the issue.