On 11 March 2016 the South African Revenue Service (Sars) announced the deletion of tariff subheading 1605.53.20 (---Other, in airtight metal containers:) and insertion of tariff subheadings 1605.53.2 (Other, in airtight metal containers); 1605.53.21 (---- Smoked); and 1605.53.22 (---- Other) to reduce the rates of customs duty on canned mussels in airtight metal containers from 25% ad valorem to free.
The reasoning for the tariff amendments can be found in the International Trade Administration Commission of South Africa (Itac) Report 513.
So if the retail price of canned mussels is not reduced, you know that someone is profit taking, which is not the intention of a tariff reduction.