Invasive Species &
Marine Shipping #invasivespecies #ballastwater #biofouling #clearfacts


The past three decades have seen a fourfold increase in marine shipping traffic as the demand for global trade continues to grow. But ships transiting the ocean from port to port can arrive carrying more than just their intended cargo.

Without careful measures, ships can unintentionally transport foreign species to new environments – where without natural predators, these “invasive” species can threaten local ecosystems and damage the environment, the economy and human health.

This site’s purpose is to share objective information about invasive species in Canadian waters – how they get here, what threats they pose and how they can be countered – and to encourage informed conversations about these issues.

This site was created by Clear Seas Centre for Responsible Marine Shipping, an independent research centre that promotes safe and sustainable marine shipping in Canada.

Invasive Species in Canadian Waters

Canada is a maritime trading nation. Every day, commercial vessels from all over the world enter our coastal waters, rivers and lakes carrying goods to and from the country. Each of these vessels has the potential to cause harm by unintentionally introducing invasive species.

Today, invasive species are considered one of the key threats to natural biodiversity in aquatic environments, which affects the stability of ecosystems and the economy. In Canada, disruptions caused by aquatic invasive species have an estimated cost of $5.5 billion per year from 16 invasive species alone.

As the volume of vessel traffic in Canadian waters continues to grow – particularly in sensitive areas such as the Arctic – there is an increasing need to understand and prevent the potentially devastating impacts of these foreign species.

  • So where do invasive species come from?
  • How do they get to Canada, and why do they cause so much damage once they arrive?
  • What can be done to stop the spread of these invaders and limit their negative impacts?

What Makes a Species “Invasive”?

Species have long used the world’s ocean and waterways to make their way around the planet. Until recently, these movements were relatively slow and infrequent, driven mainly by natural processes like currents and winds or hitching a ride on a whale or a log.

The explosion of human activities on the seas – most notably, commercial marine shipping – has vastly increased the opportunities for species to take refuge on or inside vessels and travel the world.

When a species – whether animal, plant or micro-organism – arrives in a new aquatic habitat, several outcomes are possible. It can:

  • Find its new surroundings uninhabitable and die off;
  • Survive in low numbers with little to no impact; or
  • Thrive and its population can grow and take over – harming its new environment in a variety of ways.

When a new species flourishes and begins changing or damaging its new environment, it is referred to as “invasive”. Once established in a new environment, invasive species can cause damage in a number of ways. For example, they can:

  • Reduce biodiversity;
  • Threaten existing species;
  • Degrade water quality and habitats;
  • Damage infrastructure such as piers as well as power, water and navigation systems;
  • Reduce waterfront property values;
  • Reduce opportunities for recreation;
  • Reduce productivity in resource sectors such as fisheries and aquaculture;
  • Lead to trade restrictions; and
  • Introduce diseases.

Impacts of Invasive Species Worldwide

Over 80% of the world’s marine ecoregions have been impacted by at least one harmful invasive species. Some regions have been impacted by many.

Number of known harmful invasive species:

0 5 10 15 20 25 30 35 40 45 50 55

How Do Species Invade?

Invasive species can be introduced to new aquatic environments in a number of different ways including:

  • Natural ocean currents
  • Use of live bait
  • Human release of live species into the environment
  • Building of canals and water diversions
  • Recreational boating
  • Commercial marine shipping

Commercial marine shipping is considered to be the largest source of new and significant aquatic species invasions worldwide.

Ships move species from port to port via two main routes:

Ballast Water

Ballast water is water drawn from a vessel’s surrounding environment and stored in specialized tanks. Inside modern vessels, ballast water is critical for maintaining weight and providing stability as a ship loads and unloads its cargo and during its voyage. Aquatic species can be swept up in ballast water when it is pumped into ballast tanks and released into a new environment when the vessel needs to unload to take on cargo in a new port.


Live organisms ranging from algae and microbes to sea stars and crabs can attach themselves to ships’ hulls in a process known as “hull fouling” or “biofouling”. Species attached to vessel hulls can be transported long distances where they can then dislodge and reproduce in a new environment. In addition to the flat surfaces of a vessel’s hull, there are several nooks and crannies on a ship’s underwater surface where organisms tend to collect, including bow thrusters, rudders, propellers, intakes, and sea chests (protected, cavity-like structures, built into the hull of a vessel and covered with metal grates). Sea chests hold water used to prime pumps in the vessel and are exposed to a constant flow of seawater.

Learn more about ballast water and biofouling

Many aquatic species have been introduced worldwide through the discharge of ballast water and through biofouling. Both of these routes are important, but some species and regions seem to experience more invasions from one route than the other.

In New Zealand, biofouling was found to be responsible for about 70% of aquatic invasive species, compared to just 3% from ballast water.
In U.S. waters, hull biofouling accounted for about 35% of aquatic invasive species compared to 20% from ballast water.

Common Invasive Species in Canadian Waters

All of Canada’s coastlines and waterways have been affected by invasive species that arrived by ship. To date, the most well-known impacts have occurred in the Great Lakes.

Between 55-70% of the estimated 56 invasive species recorded in the Great Lakes since 1959 are thought to have been introduced by shipping activities. These species have caused billions of dollars of economic harm to the region.

The Atlantic and Pacific coasts have also suffered from invasive species, resulting in damage to the fisheries and aquaculture industries in these regions.

Looking to the future, higher temperatures and melting sea ice are opening shipping corridors in the Canadian Arctic, increasing the risk that species from warmer climates will be carried into this remote and sensitive region and cause damage.

Invasive Species in Canadian Waters

Learn more about important invasive species found in Canadian waters that are impacting ecosystems and economies in these regions.

Club Tunicate
European Green Crab
Zebra Mussels
Bloody Red Shrimp
Chinese Mitten Crab

Club Tunicate

Pacific & Atlantic Coasts

The club tunicate settles on the ropes of mussel aquaculture facilities in Prince Edward Island where it out-competes the cultured shellfish. This has led to economic losses for the mussel industry, which supplies over 70% of the blue mussels in the North American market. The club tunicate is also present and affects aquaculture facilities in the Strait of Georgia in British Columbia.

European Green Crab

Pacific & Atlantic Coasts

The European green crab has invaded numerous coastal regions of the world where its appetite for commercially valuable clams and crabs has threatened important fisheries. This crab has affected Atlantic fisheries since the 1980s, and more recently was found in discrete locations on the west coast of Vancouver Island. It may spread along the BC coast where it may out-compete other, commercially important crab species and damage eelgrass habitat.

Zebra Mussels

Great Lakes

Zebra mussels first appeared in the Great Lakes in the late 1980s, suspected of arriving in ship ballast water. These prolific mollusks are known for attaching themselves firmly to any solid surface, causing damage to boating equipment and piers, clogging pipes and power and water treatment plants, and damaging tourism industries. The total economic impact of zebra mussels on industries, businesses and communities in the Great Lakes region was estimated to be between $3 and 7.5 billion as of 2004.

Bloody Red Shrimp

Great Lakes

Bloody red shrimp were first detected in 2006 in Lake Ontario and Lake Michigan and have since been identified in all the Great Lakes. This species is believed to have been transported in ballast water and its impact on the Great Lakes ecosystem is not fully known. The rapid growth and reproduction of this shrimp combined with its voracious appetite for zooplankton could limit food sources for juvenile native fish species.

Chinese Mitten Crab

St. Lawrence Seaway

The Chinese mitten crab damages fisheries by consuming salmon, trout and sturgeon eggs. This crab’s burrowing can damage fish habitat and erode banks and levees. It is a host for the oriental lung fluke – a parasite that can infect humans who consume it raw or undercooked.


Arctic Coast

Several species of highly invasive barnacles were recently transported through biofouling on vessels arriving in Churchill, Manitoba. The barnacles’ survival in frigid Arctic waters suggests they could potentially establish successful populations and compete with native species for food and space, altering the delicate balance of this remote ecosystem.


Reducing Species Invasions Caused by Shipping

To combat the negative effects of invasive species, vessel owners and operators are focusing on how to reduce the likelihood that invasive species will be transferred by ship through ballast water and biofouling.

In Canada and worldwide, governments are also working to reduce the impacts and risks of species invasions by introducing guidelines and in some cases, regulations, to better handle ballast water and reduce biofouling.

Preventing Transfer through Ballast Water

There are several ways for vessel owners and operators to prevent the transfer of invasive species through ballast water:


Ballast water can be treated with mechanical, physical, chemical or biological processes either onboard ship or on shore to destroy or otherwise render inert any organisms contained in the ballast water.


Ballast water can be exchanged by replacing coastal or fresh water for open-ocean water during the voyage to limit the transfer of species from one coastal ecosystem to another.

In Canada, regulatory measures were introduced in 2006 under the Canada Shipping Act – known as the Ballast Water Control and Management Regulations – to enforce ballast water management practices. The practical and regulatory measures for ballast water management have proved to be effective. No new invasive species attributed to ballast water have been reported in the Great Lakes since these measures were introduced in 2006.

Learn more about Canadian Ballast Water Regulations

Preventing Transport through Biofouling

Innovative approaches are being applied by vessel owners and operators to reduce invasive species transport through biofouling.

Anti-fouling Coating

Application of an anti-fouling paint or other non-toxic coating to exposed, submerged surfaces is the primary means of inhibiting growth of marine life.

Biofouling Resistant Materials

Materials are selected for piping and other unpainted components to resist marine life growth.

Marine Growth Prevention Systems

In internal or niche areas such as sea chests and seawater cooling systems marine life is prevented from settling by the use of electrolysis through copper, aluminum and iron anodes.

Regular Hull Cleaning

If the hull is scrubbed before every departure, it is more likely to be clean on every arrival. The required frequency of cleaning depends on the rate of marine life growth, which is affected by travel speed, time spent at anchor or in port, and the temperature and salinity of the water the ship transits through.

Widespread recognition of the risks posed by biofouling has emerged relatively recently. While there are currently no domestic biofouling regulations in place in Canada, Transport Canada recognizes the importance of this issue and is actively engaging on a number of fronts to explore options to prevent and mitigate risks posed by biofouling.

Globally, the IMO recommends but does not yet require management practices to control biofouling.

Learn more about the IMO Biofouling Guidelines

Initiatives in Progress

There are a number of initiatives currently in place in Canada and internationally that are helping to prevent and mitigate the impacts of shipping on invasive species transfers. Here are some examples:

Port of Prince Rupert
  • In 2012, the Port of Prince Rupert entered a partnership with Northwest Community College and the Invasive Tunicate Network’s Plate Watch program to start one of the first aquatic invasive species monitoring programs on Canada’s Pacific coast.
  • Supported by Fisheries and Oceans Canada, this program collects and reports findings to a coast-wide group of experts and contributes to an early detection system for invasive species.
  • To date, no invasive species have been detected in Prince Rupert harbour, although a few have been detected in the broader area of BC’s north coast.
Green Marine
  • Green Marine’s Environmental Certification Program includes performance indicators that encourage members to take measures to reduce the risk of introducing invasive species.
  • These performance indicators recommend that domestic and international ship owners adopt accepted best practices to prevent invasive species’ introductions, including keeping an annual ballast water inventory record and participating in R&D for new ballast water treatment systems.
  • The indicators also recommend ship owners test or install ballast water treatment systems and implement anti-fouling measures.
GloFouling Partnerships Project
  • This project – a partnership between the Global Environment Facility (GEF), the United Nations Development Programme (UNDP) and the International Maritime Organization (IMO) – will focus on building capacity in developing countries to implement the IMO Biofouling Guidelines.
  • Participating countries will work together to develop legal, policy and institutional reforms to address biofouling issues in their regions.
  • Building on the success of the 7 year GloBallast Partnerships Project which worked to implement the IMO Ballast Water Convention, this new project was approved in May 2017 and is now going through a detailed preparation phase before implementation.
New Zealand
  • New Zealand’s Ministry for Primary Industries (MPI) has introduced new biofouling rules for all vessels arriving in New Zealand’s territorial waters beginning in May 2018.
  • The Craft Risk Management Standard for Biofouling (CRMS) will require all vessels to arrive in New Zealand with a “clean hull” and MPI will measure compliance based on records of the vessel’s biofouling maintenance.
  • The CRMS is the world’s first national biofouling standard.
  • The CRMS applies to any vessel that will anchor, berth or be brought ashore in New Zealand after a voyage originating outside New Zealand’s territorial waters.
State of California
  • New biofouling regulations came into effect as of January 1, 2018 to address concerns about the impacts of biofouling in California’s waters.
  • These regulations adopt a new annual vessel reporting scheme and require development of a biofouling management plan and related record keeping consistent with the IMO Biofouling Guidelines.

About Clear Seas

Clear Seas Centre for Responsible Marine Shipping is an independent research centre that promotes safe and sustainable marine shipping in Canada.

Clear Seas was established in 2014 after extensive discussions among government, industry, environmental organizations, indigenous peoples and coastal communities revealed a need for impartial information about the Canadian marine shipping industry.

Clear Seas received seed funding in 2015 through equal contributions from the Government of Canada (Transport Canada), the Government of Alberta (Alberta Energy) and the Canadian Association of Petroleum Producers. Our funders saw the need for an independent organization that would be a source of objective information on issues related to marine shipping in Canada.

As an independent research centre, Clear Seas operates at arm’s length from our funders. Our research agenda is defined internally in response to current issues, reviewed by our research advisory committee, and approved by our board of directors.

Our board of directors is composed of scientists, community leaders, engineers and industry executives with decades of experience investigating human, environmental and economic issues related to our oceans, coastlines and waterways.

Our reports and findings are available to the public at

Sources & Citations

  1. Tournadre, J. (2014). Anthropogenic pressure on the open ocean: The growth of ship traffic revealed by altimeter data analysis. Geophysical Research Letters, 41: 7924-7932.
  2. Fisheries and Oceans Canada. (2018). A Canadian Action Plan to Address the Threat of Aquatic Invasive Species.
  3. Molnar et al. (2008). Assessing the global threat of invasive species to marine biodiversity. Frontiers in Ecology and the Environment. 6(9): 485-492.
  4. Frey et al. (2014). Fouling around: vessel sea-chests as a vector for the introduction and spread of aquatic invasive species. Management of Biological Invasions. 5(1): 21-30.
  5. Sea chest image courtesy of Angela Gillham, Maritime Industry Australia Ltd.
  6. Transport Canada. (2010). Ballast Water Defined.
  7. Deadweight tonnage (DWT) is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.
  8. MIT Sea Grant Coastal Resources. (2002). Marine Bioinvasions Fact Sheet: Ballast Water.
  9. Demiriel et al. (2017). Predicting the effect of biofouling on ship resistance using CFD. Applied Ocean Research. 62: 100-118.
  10. Cranfield et al. (1998). Adventive marine species in New Zealand. NIWA Technical Report 34.
  11. Fotonoff et al. (2003) In Ships or on Ships? Mechanisms of transfer for non-native species to the coasts of North America. In Ruiz GM and Carlton JT (Ed.s) “Invasive species: vectors and management strategies”. Washington, Island Press.
  12. Bailey et al. (2011). Evaluating Efficacy of an Environmental Policy to Prevent Biological Invasions. Environmental Science & Technology. 45(7): 2554-2561.
  13. Transport Canada. (2017). Ship-mediated Introductions.
  14. Fisheries and Oceans Canada. (2006). An Economic Analysis of the Mussel Industry in Prince Edward Island. Policy and Economics Branch, Gulf Region Department of Fisheries and Oceans, Moncton, New Brunswick.
  15. U.S. Fish & Wildlife Service. Chinese Mitten Crab.
  16. Fisheries and Oceans Canada. (2016). Chinese Mitten Crab.
  17. Government of Canada. (2004). An Alien Invasive Species Strategy for Canada.
  18. Bloody red shrimp (Hemimysis anomala) image courtesy of S. Pothoven, GLERL.
  19. Ontario’s Invading Species Awareness Program. (2018). Bloody Red Shrimp.
  20. Transport Canada. (2010). Alien Invasive Species.
  21. Chan et al. (2015) Relative importance of vessel hull fouling and ballast water as transport vectors of nonindigenous species to the Canadian Arctic. Canadian Journal of Fisheries and Aquatic Sciences. 72(8): 1230-1242.
  22. Transport Canada. (2015). Ballast water and the Great Lakes-St. Lawrence Seaway System.
  23. Government of Canada. (2017). Ballast water management of ships: international convention.
  24. International Maritime Organization. (2011). 2011 Guidelines for the Control and Management of Ships’ Biofouling to Minimize the Transfer of Invasive Aquatic Species.
  25. International Maritime Organization. (2018). Biofouling.