Testing for toxicity to fish in our laboratories

When an Environment and Climate Change Canada enforcement officer becomes aware of an alleged offence under the pollution prevention provisions of the Fisheries Act, they collect information to verify compliance with the Act, or as evidence of an offence. Under the Act, it is prohibited to deposit a deleterious, or harmful, substance into fish-bearing water or any place where it can enter that water. As part of an inspection, officers may decide to collect samples of spilled substances or effluents and send them to our laboratories to perform toxicity testing.

Environment and Climate Change Canada laboratories are accredited under international quality management standards for environmental testing. From the moment a sample is collected until it is analyzed, records are kept to show the movement of the sample from collection to testing, interpretation, and results. Enforcement officers collect samples in the safest way possible; this means that sample sizes can vary, depending on how easily and safely they can be collected.

Once the laboratory receives the sample, it is logged into a database and tested within five days of sample collection to ensure accuracy of results. Toxicity tests are conducted by exposing either Rainbow Trout or Daphnia magna, a water flea, to the sample of the suspected deleterious substance. The trout are exposed for a 96-hour period, and the Daphnia magna for a 48-hour period. A sample is considered toxic to fish if it kills more than 50 percent of the fish or Daphnia magna when it is not diluted. However, a substance does not have to kill fish to be considered deleterious, or harmful, to fish.

Once testing is complete, Environment and Climate Change Canada scientists and toxicologists analyze, review, and validate the report to ensure its accuracy before providing the results to the enforcement officer. When the final results are shared with the enforcement officer, they will decide if the case requires more information gathering, including sampling. If there is sufficient evidence of an alleged violation, they take appropriate enforcement action in accordance with the Compliance and Enforcement Policy.

Quick facts

• A deleterious substance can be any substance, such as oil, chemicals, or pesticides, that if added to water would degrade or alter the water quality to the point that it could harm fish.
• A toxicity test, also known as a bioassay, is a test that measures the impact of a substance on living organisms, such as Rainbow Trout and Daphnia magna, under defined conditions.
• Rainbow Trout are a representative species for toxicity testing because they are native to North America. They inhabit the waters of all Canadian provinces and have been introduced around the world. Rainbow Trout used for testing are obtained from hatcheries.
• Daphnia magna inhabit waters across North America and are an important component of aquatic communities.
• It is important to note, however, that references to toxicity testing on fish should not be applied in a human health context. Fish toxicity tests are performed in a controlled laboratory setting to establish a legal threshold for potential enforcement actions under the Fisheries Act.

Toxicity testing for deleterious, or harmful, substances in water frequented by fish

Infographic: How Environment and Climate Change Canada tests for toxicity to fish (PDF, 1.3 MB)

This infographic shows a river flowing downwards. Along the river bend, the different steps that a water sample will go through for toxicity testing are indicated.

Before Step 1, there is an image of a female enforcement officer in her uniform with text: Follow along as enforcement officer, Nicky, collects and submits a water sample to our laboratory for testing. This test will help her determine if there is a potential offence under the pollution prevention provisions of the Fisheries Act.

Step 1 – Collection: Nicky collects water samples from the source of possible pollution and in the body of water that is of interest and catalogues the sample for storage and future testing. The image shows Nicky on the shore collecting water with a pail and a cooler.

Step 2 – Submission: Nicky submits the sample to her scientist colleague, Charlie, for testing at one of our accredited labs. The image shows Nicky in front of a Government of Canada building bringing the cooler on a dolly and giving it to Charlie.

Step 3 – Testing: Charlie begins testing the water sample by exposing either Rainbow trout or water fleas to the sample. The image shows Charlie in a lab next to a water tank as he collects fish with a fishnet. Along with the image, there is a fact bubble with text: “Rainbow trout and water fleas are common freshwater species native to North America. During testing, Rainbow trout are exposed to the sample for a 96-hour period and water fleas for a 48-hour period.”

Step 4 – Analysis: When the testing period is complete, Charlie returns to complete the sample analysis. If more than 50% of the fish or water fleas have died, the sample is considered toxic to fish and is also deleterious. The image shows Charlie with a female colleague examining the water tank. In the water tank fish are floating on their side, meaning they are dead. Along with the image there is a fact bubble about deleterious substances: “A substance does not have to kill fish to be deleterious. A deleterious substance is any substance that when added to water degrades or alters water quality enough that it could harm fish or their habitat.”

Step 5 – Quality Assurance and Control: Ali reviews the data gathered by Charlie and Emma to ensure its quality and accuracy. He does this by checking to make sure the fish or flea samples were healthy before testing. He also has to ensure the quality of the control. This process takes time to ensure the validity of the testing and results. The image shows Ali sitting in front of a computer and looking at the data. Along with the image there is a fact bubble with the following text: “Each sample that is tested has a corresponding control set-up. This is a secondary tank that uses clean lab water as opposed to the sample submitted by the officer.”

Step 6 – Report: Ali gives Charlie the final report. Charlie must share this report directly with Nicky. The image shows Charlie handing Nicky, the enforcement officer, the final report in front of a Government of Canada building.

Step 7 – Evaluation: Nicky will document and evaluate the results and determine next steps based on legal requirements. The image shows Nicky sitting at a desk with her laptop looking at the report. She is thinking: “Is there a potential offence under the Fisheries Act?”