Vegetarianism and beer a yeasty flavour. Finings are used to clear the beer of yeast – there are a variety of agents used as finings, including silicon dioxide, gelatin, polyclar, and isinglass. Isinglass is the most common fining used to clear cask ale. Isinglass is produced from the swim bladders of fish, usually sturgeon, though also those in the polynemidae, sciaenidae and siluridae families; as it is an animal product, cask ale cleared with isinglass is not considered vegetarian. A brewer may also use some form of animal product in the later stages of beer processing, such as glycerol monostearate, which is used
Swim bladder and a swim bladder. The cartilaginous fish (e.g., sharks and rays) split from the other fishes about 420 million years ago, and lack both lungs and swim bladders, suggesting that these structures evolved after that split. Correspondingly, these fish also have both heterocercal and stiff, wing-like pectoral fins which provide the necessary lift needed due to the lack of swim bladders. Teleost fish with swim bladders have neutral buoyancy, and have no need for this lift. Sonar operators, using the newly developed sonar technology during World War II, were puzzled by what appeared to be a false sea floor 300–500