Michael,

Just found this old thread. To answer your question, the High Seas Fleet conducted a destroyer operation on November 12, 1917. Per "Der Krieg in der Nordsee, Band 7", with the IX. Flottille sank a number of fishing vessels. Judging by "Lloyd's War Losses: The First World War", the correct number seems to be five: JACOBA, STATENDAM, VAN DER DUIN VAN MAASDAM, GEERTRUIDA, and CORNELIS BART.

Certain Dutch sources use "Getorpedeerd" for any non-mine war loss, including ships torpedoed as well as those stopped and scuttled.

Detailed information on HUIBERTJE is here: [uboat.net]

Best wishes,
Michael