The vase could be either Kosta, Orrefors, Johansfors, Sea Glasbruk or Iittala, but Kosta is the most likely as they often supplied unsigned blanks for engraving to decorator shops of which there were many. The flat surface on the oval section is particularly suited for decoration.
Unable to figure out what the mark is - I'm not convinced by Frank's leaping salmon. Have you tried putting the piece on a scanner under a black cloth?
I have one similar item with a minute signature which was impossble to decypher; it turned out to be Peill & Pützler commissioned for Lenox, USA, so it had both marks mixed.
And what does it mean "vase came back from fishing trip with a fish" - I want to hear the rest of the fairy tale!