What is a Sea Lice Audit?
In BC, sea lice counts are conducted on each salmon farm site at least once per month throughout the year. The Sea Lice Audit Program checks the validity of these farm numbers by performing an independent sea lice assessment and comparing audit results with data provided by individual companies.
BC CAHS’s role was as a third-party auditor, representing neither salmon farming nor regulator (government) interests. BC CAHS was responsible for sea lice audits during the transition period between the provincial government's Ministry of Agriculture and Lands and the federal government's Fisheries and Ocean transfer of jurisdiction. BC CAHS collected data during Q2 - Q4 in 2010.
Who conducted the Sea Lice Audit?
BC CAHS audit staff have extensive fish health knowledge as well as training to differentiate the various louse species found in BC, to distinguish sex of each louse and to determine basic life stages. All of this work is done on the farm site. During audits, a sub-sample of chalimus life stages may be collected at the time of the audit for further microscopic differentiation of species and life stages at the BC CAHS laboratory facility. This additional information will be added under “Comments” in the audit report.
How is the Sea Lice Audit conducted?
The audit process divides farming areas by fish health zones (as determined by the BC Ministry of Agriculture and Lands: full document here) and separates the calendar year into quarters (January-March, April-June, July-September, and October-December). In each quarter, salmon farm companies provide the names of active Atlantic salmon farm sites in each fish health zone and software is used to randomly select 25% of farms from each zone for audit. During an audit visit, twenty fish from three pens, including a reference pen, are assessed for all species and life stages of sea lice. To achieve a representative sampling from each pen, fish are seined, crowded and dip-netted. Collected fish are anaesthetized to facilitate easy handling during the assessment and to reduce stress to the animal. Of the twenty fish sampled, ten fish are assessed by farm staff and ten by the BC CAHS auditor. During assessment, each fish is physically handled so that all surfaces are examined for lice. Lice numbers on each fish, and any lice that remain in the tote after all fish are assessed, are recorded by species and life stage. Assessed fish are returned to their pen to rejoin their population and to recover from the anaesthesia. In addition, the anaesthetic bath is carefully examined for lice that may have detached from the fish and these are enumerated also.
What does the audit tell us?
From each sea lice count, an average number of sea lice per fish is determined. This average number, based on a sixty fish sub-sample of the farm’s population, is statistically representative of the average number of lice per fish on that farm during the audit visit. If this number reaches a threshold of three motile lice per fish between March and June, the farms are required to either treat with emamectin benzoate (SLICE®) or harvest. Therefore, ensuring the validity of farm-conducted lice counts through the audit process is critical to proper sea lice management on salmon farms.
Ultimately, the Sea Lice Audit Program is a check that sea lice data reported by salmon farming companies is consistent with the auditor’s results; that farm staff are conducting their audits appropriately; and that their count results are credible. For each audit date, farm staff counts are compared to auditor counts using a 2-sample T-test to determine if any significant differences exist. As audits are conducted on a quarterly basis, the average audit results from the subsample of the farms are assessed in relation to the quarter averages as reported by all the Atlantic salmon farms in the region (zone/subzone) to determine whether values are statistically different. For this comparison, if the mean abundance as determined through the audit lies within the 95% confidence intervals calculated from the mean abundance levels reported by the salmon farms, then we can say that these values are not statistically different from one another (see corresponding graphs below).
Past sea lice audit results (to Dec. 2009) and annual Fish Health Reports (from 2003 to 2009) can be found on the Ministry of Agriculture and Lands website.
Quarter 2 - 2010 Sea Lice Audit Results
Table 1 - Q2 Comparison of auditor and farmer sea lice counts on the day of the audit
Table 2 - Q2 Comparison of auditor counts to industry-reported counts during the quarter
Graphs - Show comparison of auditor counts to industry-reported counts during Q2
Quarter 3 - 2010 Sea Lice Audit Results
Table 1 - Q3 Comparison of auditor and farmer sea lice counts on the day of the audit
Table 2 - Q3 Comparison of auditor counts to industry-reported counts during the quarter
Graphs - Show comparison of auditor counts to industry-reported counts during Q3
Quarter 4 - 2010 Sea Lice Audit Results
Table 1 - Q4 Comparison of auditor and farmer sea lice counts on the day of the audit
Table 2 - Q4 Comparison of auditor counts to industry-reported counts during the quarter
Graphs - Show comparison of auditor counts to industry-reported counts during Q4
Quarter 1 - 2011 Sea Lice Audit Results
Table 1 - Q1 Comparison of auditor and farmer sea lice counts on the day of the audit
Table 2 - Q1 Comparison of auditor counts to industry-reported counts during the quarter
Graphs - Shows comparison of auditor counts to industry-reported counts during Q1