Guinness is Irelands unofficial beer, and is very popular worldwide, with consumption numbers drastically increasing during St. Particks day. There is an interesting and unusual fact about it's making I bet you didn't know however, and if you're a vegan or a vegetarian this might make you think twice before ordering. Since the mid to late 19th century, air-bladders of fish (the parts that produce sound) also known as isinglass, have been used to clarify Guinness beer. Beluga was the preffered fish for the extraction of it's isinglass until William Murdoch introduced the cheaper Cod substitute in 1975. Although the mucous like substance sinks to the bottom of the cask after the clarification process is over, there might still be traces of fish bladder remaining in the beer.