Benthic Monitoring

Fisheries and Oceans Canada (DFO) monitors and assesses seabed, or “benthic” impacts to minimize the effects of fish farms on the environment. The Department’s conditions of licence for marine finfish aquaculture require farm operators to monitor all operational sites at peak production, when the greatest environmental impact is most likely to occur. All industry-generated reports and video data are assessed by DFO staff for compliance with licence conditions.

Industry-conducted benthic monitoring results

In addition to the monitoring and reporting required of licence holders, DFO staff biologists conduct field audits to collect and assess sediment samples and video data.

DFO audits fulfill four purposes:

  1. to compare industry-generated data with DFO-generated data to ensure procedures are being followed correctly and that there is correlation between the two data sets;
  2. to determine if the appropriate compliance sampling stations or transects are being utilized by industry;
  3. to investigate sites with poor environmental performance or issues with compliance; and
  4. to learn more about benthic impacts during different times of the production and the site recovery cycle.

These tables contain the results of DFO’s annual benthic audits

If the thresholds outlined in licence conditions are exceeded, DFO requires that the site be fallowed (left empty) until further monitoring shows that sufficient recovery of the seabed has occurred. These tables lay out the actions required when thresholds are exceeded for benthic monitoring at soft and hard-bottom sites:

To learn more about DFO’s benthic monitoring program and the procedures and protocols used to collect data for these reports, click here. [link to “DFO benthic monitoring - sampling procedures and protocols” below]

Two DFO biologists conduct benthic monitoring at a finfish aquaculture facility

Two DFO biologists conduct benthic monitoring at a finfish aquaculture facility

The Importance of Benthic Monitoring

Fish feces and other forms of organic enrichment fall on the seabed beneath aquaculture sites. Some of this material is broken down by organisms that live on or in the seabed sediments in a process similar to the way worms and bacteria in a backyard compost bin convert organic waste into soil. However, if waste is too great or settles too quickly for the local environment and species to handle, it may accumulate in the area under and surrounding the farm – primarily within 30 metres.

While many species that live on the ocean floor, such as crabs, prawns and bottom-feeding fish, can move away from the affected area, organisms that can’t relocate can be harmed by excess organic enrichment.

DFO’s benthic monitoring program is designed to limit the location, area, and intensity of impact created by fish farms to the seabed and to support sustainable aquaculture by maintaining healthy ecosystems.  In addition, the Department assesses siting proposals for new marine finfish farms to manage benthic impact away from sensitive or critical species and habitats, such as eelgrass beds, shellfish beds, glass sponge reefs and juvenile rockfish nurseries. Industry has also taken steps to reduce its impact on the seabed, such as reducing the amount of fish food waste on farms.

There are two general seabed types in B.C. One is a soft-bottom seabed, where enough mud, clay, sand, or sediment is present that it can be physically scooped up by a sampling device. The other is a hard-bottom seabed, where the majority of the sea floor is gravel, cobble, boulder or bedrock, and sampling devices cannot grab samples.

Compliance levels for soft-bottom sites are based on the level of sulphides in a sample. For hard-bottom sites, benthic compliance thresholds are set based on the visual presence of specific types of worms and bacteria.  

Learn more about sampling procedures and protocols for soft and hard-bottom sites and for DFO benthic audits.