We do get sprats here in China but imported, like yours from the Baltic region. Yours were Latvian as is this brand available here
or from Russia.
They are also often mislabelled as herring or even sardines. In fact the Chinese name for them 西鲱 (xī fēi), literally translates as 'Western herring'. The two species do inhabit the same waters but are unrelated. The same Chinese name is also sometimes used for yet another unrelated species, shad.
Confusion reigns.