After harvest, sites will report the difference between stocking and harvest counts that cannot be explained or accounted for.
Most unexplained loss can be explained by the margin or error in the counting machines used during stocking and harvest, which is 2%. Aquaculture Stewardship Council certification includes public reporting of certain environmental criteria which are particularly important for protecting the health and genetic integrity of wild populations. The standard requires transparency about unexplained loss of salmon to help the farm and the public understand trends related to the cumulative numbers of losses of fish that go unnoticed during production.
The ASC requirements include:
Estimated unexplained loss of farmed salmon is made publicly available
The reporting of the unexplained loss should be made after harvesting. Unexplained loss is calculated as: number of smolts minus mortality minus harvest.
The calculation shall ensure control of the fish and uncover all loss of fish that cannot be explained or documented.