Aquatic Invasive Species

zebra mussels


The Risk in Maryland and the Mid-Atlantic

Aquatic invasive species pose a significant environmental and economic threat to the ecosystems and communities of Maryland, the Mid-Atlantic region, and beyond.  

Non-native or “exotic” species are plants, animals, or microbes that have been transported from one geographic region to an area where they did not live previously. The Chesapeake Bay watershed has become home to many non-native species — some innocuous, some beneficial, but others destructive beyond our expectations.

When a non-native species is introduced into a new habitat and the environment is free of natural competitors or controls, the species may grow and spread rapidly.  When these species outcompete or prey upon native species, disrupt ecosystems, and reduce biodiversity, they are considered invasive.

Aquatic invasive species (AIS) live primarily in water. Once they are introduced to a water body, it is very difficult to control their spread or completely eradicate them.  Therefore, preventing the introduction and spread of these species is the best line of defense.

The Chesapeake Bay has become home to more than 200 known or possible invasive species. Some of these species, such as the weined rapa whelk (Rapana venosa) and the Japanese shore crab (Hemigrapsus sanguineus), probably arrived in the ballast-water tanks of ocean-going cargo ships that docked in Baltimore.


Six Species of Concern

Six species have been identified as causing, or having the potential to cause, significant degradation of the Chesapeake Bay ecosystem. Maryland Sea Grant produced the fact sheets below for each of these species. The information in the fact sheets came out of a workshop co-sponsored by Maryland Sea Grant and the U.S. E.P.A. Chesapeake Bay Program in 2002. For detailed information about the six species, read the full workshop report here: Invasive Species in the Chesapeake Bay Watershed: A Workshop to Develop Regional Invasive Species Management Strategies.  Pdfs of fact sheets for individual species are included below.


What’s Being Done In The Mid-Atlantic Region?

  • Preventing AIS Introduction Through Vector Management: Live Bait in the Mid-Atlantic Region

Scientists from Maryland Sea Grant and its partner institutions are studying the live bait trade in the Mid-Atlantic region as a pathway for invasive species. The project seeks to reduce the spread of certain invasive species by improving understanding of how they are spread by the packaging, transport, sale, and disposal of live marine bloodworms (Glycera dibranchiate).

Bloodworms are harvested in Maine and packed in brown algae known as wormweed (Ascophyllum nodosum), which is found in the same region. The bloodworms are then shipped throughout the United States and Europe. The algal packing material often contains “hitchhiking organisms,” such as the European green crab (Carcinus maenas) and the rough periwinkle snail (Littorina saxatilis), which may become invasive when introduced into new environments. 

One goal of this project is for the project scientists to work with bait shop owners and anglers to spread the word: the best way to prevent these aquatic invasions is for fishers to throw away unused worms and seaweed packaging in the garbage. This simple action will help protect fish and preserve the natural habitats where they live.

Working with Sea Grant programs from Delaware, New Jersey, North Carolina, Pennsylvania, and Virginia, the research team will develop a management plan for the bloodworm trade focused on education and outreach to help reduce the spread of unwanted aquatic species in the mid-Atlantic. The development of this management plan may serve as a model for management of other live bait and further reduce the introduction of aquatic invasive species.

Read additional details about the project here, where you can download brochures and posters to help spread this message.


  • Rapid Response Plan For Aquatic Invasive Species

Although avoiding invasive species introductions is key, natural resource managers must be prepared to take action when prevention measures fail.

Maryland Sea Grant has taken a lead role in a regional effort to control aquatic invasive species. With the Mid-Atlantic Panel on Aquatic Invasive Species (MAP), we created a rapid response plan for agencies and jurisdictions in the Mid-Atlantic region. The plan offers guidelines for how they can respond quickly and effectively to an intentional or unintentional aquatic invasive species introduction.

These guidelines are described in the Rapid Response Plan for Aquatic Invasive Species: A Maryland Example. One of its features is a “decision tree,” which offers decision makers a three-step process for deciding whether to take action on aquatic invasive species.

States in the Mid-Atlantic region and beyond can use this rapid response plan as a tool for developing their own versions. A template version of the plan allows agencies to tailor it to address their specific needs. (Red text indicates information that they should customize.)


  • Aquatic Invasive Species in the Mid-Atlantic: Vector Management Workshop

Maryland Sea Grant hosted a workshop in 2009 that focused on examining and controlling exotic species vectors. The workshop, sponsored in partnership with the Mid-Atlantic Panel on Aquatic Invasive Species, drew experts from throughout the region and beyond. Participants detailed specific research, management, and education and outreach actions for the major AIS vectors, or pathways, in the Mid-Atlantic.

Read the final report for the workshop:

Preventing Aquatic Species Invasions in the Mid-Atlantic: Outcome-Based Actions in Vector Management


For Additional Information





  • Alien Ocean: An introduction to the issue of exotic marine species, with a focus on the ballast water of large ships. 
  • Alien Estuary: A focus on the Chesapeake Bay and efforts to understand exotic invasions in the estuary.


Selected Websites:


Photograph, United States Geological Survey

The Blue Crab: Callinectes Sapidus

An essential resource for researchers, students, and managers.  Get your copy today!

pile of cooked crabs