Fish bladders are sometimes used in winemaking.
Answer: True.
We know, it sounds bad; but it isn’t. Isinglass, a substance obtained by drying the bladders of sturgeons, is sometimes used in winemaking, particularly for clarifying and fining wines. Winemakers can use a number of substances for this purpose—among them, casein (a milk protein), egg whites, and bentonite (an absorptive clay).