Public Reporting on Aquaculture - Sea Lice

Fisheries and Oceans Canada’s (DFO’s) conditions of licence for marine finfish aquaculture contain monitoring and intervention requirements to minimize the potential exposure of wild and farmed fish to sea lice.

Licence holders must submit a Health Management Plan to DFO that includes sea lice management. The results of industry’s sea lice assessments of Atlantic salmon are provided to DFO monthly and posted to this website quarterly. DFO biologists and veterinarians conduct regular assessments throughout the year to verify the accuracy of licence holders’ procedures and reporting.

About sea lice reporting

Sea lice are naturally occurring parasites that reside on the bodies of both wild and farmed fish; they attach themselves to the skin, fins, and gills of fish and feed on mucus and skin. The term ‘sea lice’ actually refers to several life stages and species of parasitic copepods that may infest fish and also serve as food (plankton) for young fish. Research suggests that the salmon louse (L. salmonis) can be sustained on salmonid and non-salmonid hosts in coastal waters year-round.

Farmed salmon begin their lives in aquaculture systems on land and are transferred to ocean net pens as juveniles, lice-free. Once in the ocean, wild salmon can transfer salmon lice to farmed salmon, particularly in the autumn months as wild salmon return to the coast after foraging in the open ocean. The parasite transfer from wild to cultured fish is called ‘spill over, and the transfer of lice from farmed fish back to wild fish is called ‘spillback.’ The degree to which fish farms contribute to the prevalence of sea lice in B.C. through spillback is not known.

To minimize spillback during the out-migration of wild juvenile salmon in the spring, farm operators use techniques such as monitoring abundance, removing some fish from pens, and using in-feed anti-lice medication.

When the regulatory threshold of three motile salmon lice per fish is exceeded, licence holders must initiate semi-monthly assessments and appropriate health management procedures. These measures may include the application of an in-feed treatment, prescribed by a veterinarian and authorized for use by Health Canada, to reduce lice numbers on cultured Atlantic salmon. This proactive medication is intended to reduce the lice abundance at salmon farms during the period of wild juvenile salmon migration away from the coastal estuaries (March through June).

If fish are near harvest age and weight, farmers may instead harvest their stocks.

Learn more about the procedures and protocols used in sea lice monitoring and reporting.

Appendix

Protocols for marine licence-holders (farm operators)

Section 7 and Appendix VII of the Finfish Aquaculture Licence Conditions lays out the sea lice monitoring program that operators in B.C. must follow. Detailed protocols are designed for representative sampling of each facility’s fish population. Aside from specific instances in which operators are exempt from regular monitoring activities (see section 7.1), operators are required to abide by these protocols.

Industry monitoring of sea lice occurs routinely at conventional marine net-pen rearing facilities and occasionally at brackish sites that hold hatchery smolts before they are moved into full-strength seawater. Brackish sites are those which use water that has more salinity than fresh water, but not as much as seawater.

There are some production facilities with only two stocked pens for the production cycle, for which the current licence conditions do not require sea lice monitoring and reporting. However, in general, the industry voluntarily monitors and reports from these farms.

‘Year class’ generally refers to the size of fish and the amount of time they have spent in the marine environment. Designated broodstock are non-food fish that are not part of the production populations. Please refer to Appendix VII of the Finfish Aquaculture Licence Conditions for more information on sea lice monitoring protocols for broodstock.

At certain times, it may be risky and harmful to farmed fish to perform sea lice counts due to environmental conditions such as algal blooms and low dissolved oxygen (hypoxia). These natural phenomena can stress or kill finfish; when present, handling of farmed fish (for example, to perform sea lice counts) is curtailed.

Sea Lice Report B - average lice abundance (Year Class Two fish)

In a study of sea lice abundance on farmed salmon in fish health zone 3.3 (Broughton area), it was determined that season, area, and length of time the salmon were in the ocean influenced abundance. Sea lice abundance is expected to be higher on older fish. It is therefore appropriate, when generating estimates of zone level abundance, to calculate the average abundance from the younger fish separately from the older fish. Graphing the average abundance from the Year Class Two fish represents the higher abundance values.

Confidence intervals (shown as bars on DFO counts) are derived from the variability in the lice number between the fish counted. The bars represent the margins of error for the abundance stated.

Sea Lice Report C – DFO sea lice assessments at farms

DFO performs random quarterly checks of active Atlantic salmon farms to verify the accuracy of industry reporting. For the purpose of sea lice assessment, an ‘active’ farm is a facility that contains fish for at least 30 days, in a minimum of three pens, during the three-month period (i.e., calendar quarter) in which the lice assessment will occur.

In April, May and June, 50 per cent of the active Atlantic salmon farms in B.C. (about 50 farms) are selected for lice assessment. In each of the seven coastal fish health zones, the number of farms selected within a zone is determined by the proportion of the total number of active farms in the province that are present in that specific zone. For example, if a zone contains a third of the total number of active farms in B.C., then a third of the farms chosen for assessment by DFO would be randomly selected from that zone. This ensures that checks occur in all coastal zones and that each farm has an equal probability of being selected.

For the remainder of the year, DFO conducts lice assessment spot checks at a minimum of one farm in each of the seven fish health zones each quarter. Sea lice monitoring on farms follows random sampling principles; assessment and counts from a minimum of 20 fish per pen provide the estimate for lice abundance in the sampled pen.

When counting lice, four reporting categories are considered:

  1. Motiles. All free-moving life stages of Lepeophtheirus salmonis (salmon louse), including all females.
  2. Females. All adult female lice, with or without egg strings, of Lepeophtheirus salmonis.
  3. Chalimus. Attached early stages of species of Lepeophtheirus and Caligus. (Note: for early life stages, the differentiation between species of Lepeophtheirus requires molecular techniques, and the differentiation between chalimus stages of the most common copepods on Atlantic salmon, Lepeophtheirus salmonis and Caligus clemensi, is not practical during cage-side inspections. In other words, and for practical reasons, chalimus counts represent all lice species that may be present at the time.)
  4. Caligus. All motile life stages of Caligus clemensi found.

Between March 1 and June 30, if the observed number of motile Lepeophtheirus salmonis reaches an average farm abundance of three or more per fish, licence holders must inform DFO within five calendar days of discovery. Caligus lice are transient and are considered to be of little concern to salmon. Their abundance is routinely recorded and reported but no additional action is expected of the farmer.

The monitoring of adult female Lepeophtheirus salmonis is also valuable for trend analyses and to compare data with that of other regions, some of which monitor adult female lice more than motile lice.

Sea Lice reports

The Industry Sea Lice Report is updated monthly. It shows which Atlantic salmon farms were actively raising fish during the month and the results of industry's monthly sea lice monitoring.


The DFO Sea Lice Audit Report is posted quarterly. It shows the results of DFO’s random quarterly lice audits, which coincide with one of the licence holder's numerous scheduled counts. To assure quality, farm staff count lice on 50 per cent of the selected fish and DFO staff count lice on the other half.

Please note: prior to 2016, industry and DFO audit data were provided in a single report.

2015 Sea Lice Abundance Count Data - Click to see reports
2014 Sea Lice Abundance Count Data - Click to see reports
2013 Sea Lice Abundance Count Data - Click to see reports
2012 Sea Lice Abundance Count Data - Click to see reports
2011 Sea Lice Abundance Count Data - Click to see reports

The Average Sea Lice Abundance Graphs show average sea lice abundance on the older, larger fish in each coastal fish health zone, using results of industry reports and DFO’s random sea lice assessments. During DFO assessments, for quality assurance purposes, farm staff count lice on 50 per cent of the selected fish and DFO staff count lice on the other half.

Average Lice Abundance 2012 (Year Class Two fish)- Click to see data
Average Lice Abundance 2011 (Year Class Two fish)- Click to see data

Learn more about procedures and protocols for the Average Sea Lice Abundance Graphs


The Summary of DFO Sea Lice Assessment Activities shows the number of Atlantic salmon farms audited in B.C. and the number of live fish assessed for lice at those farms.

Learn more about procedures and protocols for the Summary of DFO Sea Lice Assessment Activities