Transport Canada protects Canadian waters by limiting the introduction and spread of aquatic invasive species by large vessels. One of the main ways that invasive species arrive in Canadian waters is from vessel biofouling.
“Biofouling” is the build-up of microorganisms, plants, algae, and animals on surfaces that are exposed to water, like a vessel's hull. Since biofouling begins to accumulate within hours of a vessel being in water, all vessels can introduce and spread non-native species. These species can become invasive and harmful in their new environments.
Biofouling also increases vessel drag, leading to increased fuel consumption, greenhouse gas emissions, operating costs, and underwater noise.
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How Canada manages biofouling
The federal government and Canada’s ports each play a role in addressing the threat of aquatic invasive species. Transport Canada has taken a leading role in shaping how biofouling is managed in Canada and around the world. We’re also studying risks from biofouling and biofouling management practices and researching new technologies that can help address these risks.
In-water cleaning of vessels
Cleaning a vessel in-water can help manage biofouling, but this process can also release organisms and contaminants into the environment.
To address this risk, and after engaging with stakeholders in 2021, we finalized the Voluntary Guidance for Relevant Authorities on In-Water Cleaning of Vessels. Although all vessels should use best practices to manage biofouling, this guidance only applies to in-water cleaning for vessels that are more than 24 metres long.
It recommends cleaning early, when only microfouling (a build-up of slime on a vessel's hull made up of tiny organisms) is present. Cleaning microfouling presents a lower risk of releasing contaminants and introducing aquatic invasive species.
If a vessel has a build-up of macrofouling (an easy-to-see build-up of large organisms like barnacles and seaweed or algae), cleaning should be performed using technology that captures and treats biofouling organisms to lower the risk of introducing aquatic invasive species as well as releasing contaminants. However, if the macrofouling happened locally, then cleaning without capture is an option. The guidance includes information on how to verify that cleaning technology meets the recommended criteria.
The guidance encourages relevant authorities to decide whether service providers should be allowed to operate in their waters and review requests for vessel cleanings on a case-by-case basis.
In-water cleaning with capture demonstrations
Under Canada’s Oceans Protection Plan, Transport Canada is studying the performance and environmental impacts of in-water cleaning technologies in Canadian waters. Contracts have been awarded to service providers to demonstrate effective clean and capture systems. These demonstrations will evaluate system performance on a range of vessel surface types and under a range of environmental conditions. The findings will enhance Canada’s understanding of the risks associated with in-water cleaning of biofouling and inform the development of science-based policies that align with international best practices.
International leadership
Canada is working closely with key partners internationally to advance policies and approaches to manage biofouling in a responsible way. Canada helped develop the International Maritime Organization's 2023 Guidelines for the control and management of ships' biofouling to minimize the transfer of invasive aquatic species. The guidelines aim to reduce the spread of invasive species by improving how ships manage biofouling. They replace the older 2011 guidelines and help set a global standard.
The 2023 guidelines recommend that ship operators:
- choose an anti-fouling system that meets their ship’s needs
- control biofouling growth in hard-to-reach areas
- keep a biofouling management plan and record book
- perform regular maintenance, cleaning, and inspections
- design ships that reduce biofouling, and
- train crew on how to manage biofouling
Transport Canada supports the voluntary uptake of these guidelines by vessels in Canadian waters.
Canada also helped develop the International Maritime Organization’s Guidance on In-Water Cleaning of Ships’ Biofouling, approved in April 2025. This document encourages safe and eco-friendly cleaning of ships while they’re still in the water.
In April 2025, the International Maritime Organization also agreed to start creating a legally binding framework for ship biofouling. Canada will take part in this process and ask Canadians to share their thoughts. These new global mandatory requirements may also lead to updated Canadian rules.
Anti-fouling systems
Canada has signed on to the International Convention on the Control of Harmful Anti-fouling Systems on Ships. This convention regulates the use of toxic compounds in systems (including anti-fouling paints) designed to prevent biofouling from accumulating. It also requires that all ships over 400 gross tonnage use an anti-fouling system that complies with the convention.
The convention, first adopted in 2001, bans organotin compounds like tributyl tin (TBT). As of January 1, 2008, ships must either remove or seal any TBT coatings.
Since January 2023, the use of another harmful chemical, cybutryne, is also banned. These steps help protect our oceans and waterways.
In Canada, the Pest Management Regulatory Agency (PMRA), part of Health Canada, controls which anti-fouling products can be imported, sold, or used. The agency keeps a list of approved anti-fouling paints.
The convention also supports other Canadian rules. Under the Canada Shipping Act, 2001, the Vessel Pollution and Dangerous Chemicals Regulations apply to all vessels in Canadian waters and to all Canadian vessels everywhere. These regulations require:
- vessels of 400 gross tonnage or more to carry an anti-fouling certificate on board, and
- vessels under 400 tons gross tonnage, but 24 metres or longer, to carry a self-declaration of compliance on board