Lampreys! I remember eating them around 2000. You could buy them in fish mongers and they weren`t too expensive. Very unusual taste. Today they are endangered protected species. Before the war, marinated lampreys were used as a popular and cheap vodka side-dish in local bars. Wiech wrote about it many times when describing boozing customs in pre-war Warsaw.
Lampreys are parasitic jawless vertebrates, similar to leeches. Today no one remembers that they were considered edible. Back in days of yore, they were appreciated in Polish cuisine for their delicate flesh. Lampreys were even popular in the royal court. The oldest cook book written in Polish, Compendium Ferculorum (recently published in English), has recipes for lampreys with gingerbread as well as cherry juice, pepper, cloves, cinnamon and sugar. In the 19th century, lampreys fried in butter were a snack to go with alcoholic beverages. It’s interesting that they were served both fresh and marinated, even though they were said to be harmful to the stomach. They’ve disappeared from Polish cuisine only because of water contamination – nowadays they’re under protection and you can only eat them occasionally, usually fried and marinated.