Indicators 4.5.14–4.5.15

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System

Water Type

Feed Dependent

Species

Indicators 4.5.14–4.5.15

by Contact on 8 October 2026

Requirement

The UoC shall, when two consecutive applications of a sea lice treatment per site have not produced the expected efficacy, carry out a bioassay to determine resistance.

The UoC shall, when bioassays determine resistance, apply an alternative sea lice treatment or immediately harvest all fish at the site.

How Do I Interpret This Requirement?

  • Expected efficacy will vary depending on the health condition of the fish and type of medicinal treatment.

    • Therefore, the site will need to review the pre- and post-treatment sea lice levels to understand and evaluate the efficacy of treatment.

      • Example: sea lice treatment with emamectin benzoate.

        • A typical baseline for the effectiveness of emamectin benzoate is a minimum of 90% reduction in the abundance of sea lice on the farmed fish.

        • To determine whether an emamectin benzoate treatment has produced the expected efficacy, the percent reduction between pre-and post-treatment sea lice levels should be calculated.

        • If the calculated percent reduction in sea lice is <90%, then the treatment did not produce the expected efficacy, and a bioassay shall be carried out to determine whether sea lice have developed resistance.

  • The person conducting bioassays should demonstrate competence, experience and training.

Evidence of Implementation

  • Records that demonstrate:

    • for cases where the site uses two consecutive applications of a sea lice treatment.

    • The observed efficacy of treatment against the expected efficacy of treatment.

      • Calculated percent reduction in sea lice levels between pre- and -post treatment.

      • The bioassay results for every case where two consecutive applications of a sea lice treatment have not produced the expected efficacy.

      • Alternative sea lice treatment or records to confirm harvest of all fish at the site when bioassays determine resistance.

      • Competence, experience and training of the person conducting the bioassay.

Auditors Should Confirm

  • Medicinal parasiticide treatments.

    • With a focus on cases where the site uses two consecutive applications of a sea lice treatment.

  • Pre-and post-treatment calculated percent reduction in sea lice levels.

  • Bioassay result for every case where two consecutive applications of a sea lice treatment have not produced the expected efficacy.

  • Alternative sea lice treatment or harvest of all fish at the site when bioassays determine resistance.

  • Competence, experience and training of the person conducting the bioassay.