Historically , herring has been one of the major protein sources in Sweden , however the elite considered herring being lower class food and consumed the herring mainly in its pickled form , staring in the mid 18th century .
Historically , herring has been one of the major sources protein in Sweden . 
 However , the elite considered it more of lower class food and did not start consuming it in its pickled form , until the mid 18th century .