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


Commercial vessels transiting the world’s oceans from port to port can transport as much as 90% of the world’s goods and products – and carry more than just 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, created by Clear Seas Centre for Responsible Marine Shipping, provides objective information about invasive species in Canadian waters – how they get here, what threats they pose and how they are countered – to encourage informed conversations about these issues.

Invasive Species in Canadian Waters

Canada is a maritime trading nation. Every day, commercial vessels from all over the world transit 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 transferring invasive species.

Today, the spread of invasive species is considered one of the key threats to natural biodiversity in aquatic environments – second only to habitat destruction. The costs to repair damage by and manage the impacts of invasive species are significant and increasing. Globally, it is difficult to estimate the financial damage from invasive species but one study concluded that invasive fish have had “pernicious ecological and economic impacts on both aquatic ecosystems and human societies.” A comprehensive database of known costs up to 2017 indicates global costs of US$1.28 trillion for all reported terrestrial and aquatic invasive species, with ongoing costs to Canada of at least $580 million per year from only aquatic invasive species.

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 the devastating impacts of these foreign species and limit their introduction and spread.

Learn more: The Government of Canada’s approach to managing aquatic invasive species

  • So where do invasive species come from?
  • How do they get to Canada?
  • Why do they cause so much damage once they arrive and what is being 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 oceans and waterways to make their way around the planet. These movements used to be 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.

Learn more: How to identify an aquatic invasive species

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 to Canada’s ecology, economy, and human well-being in a number of ways. For example, they can:

  • Reduce biodiversity and threaten existing species by introducing diseases, consuming the species or its food sources, or taking over habitat;
  • Degrade water quality and habitats;
  • Damage infrastructure such as piers as well as power, water and navigation systems;
  • Erode shorelines;
  • Reduce waterfront property values;
  • Reduce opportunities for recreation and tourism;
  • Reduce productivity in resource sectors such as fisheries and aquaculture;
  • Harm Indigenous cultures and traditional food sources;
  • Lead to trade restrictions.

Impact of Invasive Species Worldwide

More than 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 dispersal through ocean currents and water movement
  • Human release of live species (bait, pets) into the environment, either accidental or otherwise
  • Building of canals and water diversions
  • Recreational boating activity
  • 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 drawn from a vessel’s surrounding environment and stored in specialized tanks. Ballast is critical for maintaining weight and providing stability during the voyage and as a ship loads and unloads its cargo. 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 takes on cargo in a new port.


Live organisms ranging from algae and microbes to mussels and barnacles can attach 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 underwater niches on a ship where organisms can collect, including bow thrusters, rudders, propellers, intakes, and sea chests (protected cavities built into the hull of a vessel, covered with metal grates and 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 (and are not the only way invasive species can travel), 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. In a 2019 report, the ecosystem health of the Great Lakes was assessed as poor and deteriorating with reference to invasive species.

Approximately 30% of the estimated 185 aquatic non-native species established in the Great Lakes are thought to have been introduced by ship ballast water., These species have caused significant and ongoing economic and ecological harm to the region.

Learn more: Database of economic costs of worldwide biologic invasions

The Atlantic and Pacific coasts have also suffered from invasive species with damage to Indigenous and coastal communities, particularly 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 how invasive species are impacting ecosystems and economies in Canadian waters through examples of invasives of concern in different regions.

Clubbed Tunicate
European Green Crab
Zebra Mussels
Bloody Red Shrimp
Eurasian Ruffe
Chinese Mitten Crab

Clubbed Tunicate

Pacific & Atlantic Coasts

The clubbed 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. Clubbed tunicates are also present around Vancouver Island in British Columbia and affect aquaculture facilities in the Salish Sea.

Learn more: Applying Traditional Knowledge to study invasive tunicates in Haida Gwaii as part of Clear Seas’ Indigenous Internship program.

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, crabs and, most recently, salmon has threatened important fisheries, including the food, ceremonial and social fisheries of First Nations communities. This crab has drastically affected Atlantic fisheries since the 1980s and was discovered in British Columbia in the late 1990s. In recent years, this aggressive species of crab has been spreading rapidly and is found along Vancouver Island and the Salish Sea, the central coast near Bella Bella, and Haida Gwaii. Capture initiatives to reduce its impact on fisheries and eelgrass are gaining momentum.

Zebra Mussels

Great Lakes, St. Lawrence River, Lake Winnipeg, Red River and Nelson River

Zebra and quagga mussels first appeared in the Great Lakes in the 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. Zebra and quagga mussels also harm ecosystems by voraciously consuming plankton, depriving native species of food and increasing toxic algal blooms. The total economic impact of zebra and quagga mussels on industries, businesses and communities in the Great Lakes region is estimated to be in the billions of dollars. Controlling these mussels has resulted in direct costs of $408.6 million (up to 2017). These mussels have spread into lakes and rivers in Manitoba; Saskatchewan and Alberta have robust preventative programs in place and have not yet discovered any zebra or quagga mussels in their freshwater habitats.,

Bloody Red Shrimp

Lakes Erie, Huron, Michigan and Ontario

Bloody red shrimp were first detected in 2006 in Lake Ontario and Lake Michigan and have since been identified in Lakes Erie and Huron.,, 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.

Eurasian Ruffe

Lakes Erie, Huron, Michigan and Superior

A type of perch from northern Europe and Asia, the ruffe arrived in the Great Lakes in the mid-1980s in ballast water. Ruffe are adaptable, grow and reproduce rapidly, and are largely safe from predators due to a spiny dorsal fin. Ruffe impact native species by competing for food and habitat, including predation of native eggs, and can quickly become the dominant fish species, contributing to the decline of native fish.

Chinese Mitten Crab

Lake Erie, Lake Ontario, St. Lawrence River

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


Arctic Waters

Several species of highly invasive barnacles have been identified on biofouled vessels arriving in Churchill, Manitoba. The barnacles’ survival on ships 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

Actions by vessel owners and operators reduce the likelihood that invasive species will be transferred by ship ballast water or biofouling. These actions are required by regulations or informed by guidelines in Canada and internationally.

The International Convention for the Control and Management of Ships’ Ballast Water and Sediments was first established by the International Maritime Organization (IMO) in 2004 and entered into force in 2017.

In Canada, regulations have been in place through the Canada Shipping Act, 2001 – known as the Ballast Water Control and Management Regulations – since 2006 to limit the spread of invasive species. In 2021, Canada adopted new Ballast Water Regulations to replace the previous regulations and impose more stringent requirements on ships and increase compatibility between the Canadian and American ballast water regimes.

Preventing Transfer of Invasive Species through Ballast Water

Vessel owners and operators are required to prevent the transfer of invasive species by either treating or exchanging their ballast water:


Ballast water can be treated with mechanical, physical, chemical or biological processes such as filters, chemicals, ultraviolet light, electrolysis, and sounds 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.

The regulations apply to Canadian vessels everywhere and foreign vessels operating in Canadian waters that are designed to carry ballast water. Under these regulations, ships are required to:

  • Develop and implement a ballast water management plan
  • Obtain a certificate attesting that their ballast management plan meets the Convention’s requirements
  • Keep records of ballast water regulations and be subject to inspections to verify compliance with the regulations
  • Comply with a performance standard (regulation D-2 of the Convention) to limit the number of organisms discharged by 2024 (or 2030 for some domestic and Great Lakes ships).

To date, the measures for ballast water management have proven effective – no new invasive species attributed to ballast water have been reported in the Great Lakes since these measures were introduced in 2006. The water treatment required under the new Ballast Water Regulations will help prevent the spread of invasive species within Canada as well as the transfer of species from Canada to other regions, protecting global biodiversity.

Learn more about ballast water management in transboundary areas

Preventing Transfer of Invasive Species through Biofouling

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

Anti-fouling Hull 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. Prior to the International Convention on the Control of Harmful Anti-fouling Systems on Ships, in force in 2008, ship coatings had toxic components that leached heavy metals into the ocean.

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.

Hull Cleaning

Removing marine organisms from the hull can occur when the ship is in the water (at berth or underway) or less frequently when out of the water (in dry dock). 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.

More frequent cleanings maximize the ship’s fuel efficiency and mean the ship is less likely to transport species from one port to another. Advances in robotic technology are supporting the development of in-water “clean and capture“ systems, where biofouling slime is scrubbed off the ship by a robot and pumped to the surface for treatment to prevent environmental damage and invasive species transfer. This emerging practice is supported by the development of Voluntary Guidance for Relevant Authorities on In-Water Cleaning of Vessels that began in 2021.

While there are currently no domestic biofouling regulations in place, Canada recognizes that biofouling is a significant pathway for the introduction and transfer of aquatic invasive species and is working to prevent and mitigate risks posed by biofouling.

Globally, the International Maritime Organization (IMO) recommends but does not yet require management practices to control biofouling.

Learn more about the IMO Biofouling Guidelines

Initiatives UNDERWAY

There are a number of initiatives currently in place in Canada and internationally that are helping to reduce the risk of shipping as a pathway for invasive species.

Central Coast Indigenous Resource Alliance
  • The Central Coast Indigenous Resource Alliance, which consists of four First Nations – Heiltsuk, Kitasoo/Xai’Xais, Nuxalk, and Wuikinuxv – is partnering with the Province of British Columbia to implement the Marine Plan Portal (MaPP) on the Central Coast of British Columbia through a coordinated response to three aquatic invasive species: European Green Crab, tunicates, and bryozoa.
  • Ten people (Guardian Watchmen and other field staff) from the four Nations are monitoring these aquatic invaders and collecting baseline data on their presence, abundance, and damage to the ecosystem. The millennia-long connection of the four Nations to these ecosystems is integral to this work.
Invasive Species Monitoring Program
  • In 2012, the Port of Prince Rupert entered a partnership with the Coast Mountain College Applied Coastal Ecology program 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.
  • The program monitors for the presence of the European Green Crab, invasive tunicates and bryozoan species. Program participants collect and report findings to a coast-wide group of experts, contributing to an early detection system for invasive species. To date, no invasive species have been found in Prince Rupert harbour, although a few have been detected in the broader area of BC’s north coast.
Aquatic Invasive Species Performance Indicator
  • Green Marine’s Environmental Certification Program includes performance indicators that encourage domestic and international ship owners adopt accepted best practices to prevent the introduction of invasive species, including keeping an annual ballast water inventory record and participating in research and development 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
  • Initiated in 2017, this project brings together the Global Environment Facility, the United Nations Development Programme, the International Maritime Organization (IMO) and other partners including Transport Canada, to build capacity in developing countries to implement the IMO Biofouling Guidelines.
  • Participating countries are working together to develop legal, policy and institutional reforms to address biofouling issues in their regions.
National Standard for Biofouling – New Zealand
  • New Zealand’s Ministry for Primary Industries introduced the world’s first national standard for biofouling rules for vessels arriving in the country’s territorial waters in May 2018.
  • The Craft Risk Management Standard for Biofouling (CRMS) requires all vessels arriving in New Zealand to have a clean hull, and applies to any vessel that will anchor, berth or be brought ashore after a voyage originating outside of New Zealand’s territorial waters.
Marine Invasive Species Program Update – California
  • New marine invasive species program updates came into effect as of January 1, 2022, to address ballast water and vessel reporting requirements in California’s waters.
  • The State’s biofouling management plan and invasive species programs are considered to be more stringent than U.S. and International Maritime Organization regulations.

About Clear Seas

Clear Seas Centre for Responsible Marine Shipping is an independent not-for-profit research centre that supports safe and sustainable marine shipping in Canada.

Clear Seas was launched in 2015 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. Learn more about the organization’s research, team and funders, here.

Sources & Citations

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  9. Sea chest image courtesy of Angela Gillham, Maritime Industry Australia Ltd.
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  19. This map does not illustrate the full extent of the range of the example species nor does it show all the invasives species of concern in Canadian waters.
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  27. Bloody red shrimp (Hemimysis anomala) image courtesy of S. Pothoven, GLERL.
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