Swim, gas or air bladders of fish such as the Sturgeon, Cat fish, Drum fish, Threadfin, Cod and Totoaba are all fish maws. Bladders of such bony fish are filled with gas, and their purpose is to control the fishes’ underwater buoyancy and stability.

The bladders are extracted from the killed fish, processed and dried in various shapes for particular uses. One such product is isinglass, a collagen utilised in the making of drinks and foods. In fact, isinglass (and fish maw) is considered one of the traditional fishery by-products along with fish meal, and fish body & liver oils.

Isinglass is supplied in a number of forms: ready-to-use liquid, concentrated liquid, dried flocculated particles, powder, freeze-dried powder or granules.

In drinks, isinglass is used in the clarification or fining process of beer and wine production. Beer is produced in a brewery through fermentation of starches from malted grain to which brewer’s yeast (micro-organism – different for ale and lager) is added. A clarifying agent (animal/plant) is essential to get rid of the cloudy appearance.

Non-animal finings do exist – seaweed, bentonite or kaolin, diatomaceous earth, cellulose pads, paper and membrane (micro-porous plastic films) filters – although they are not frequently used.

Muscovite is also known as isinglass, a form of mica that is often found in very thin, transparent sheets, and somewhat elastic in nature. Russia and India mine sheets of mica.

In foods, isinglass could be utilised as a form of gelatine.

For restoration of artwork, isinglass glue obtained from the Russian Sturgeon is considered far superior to rabbit skin glue because it is said to be of a high quality, blood and rust free.

The fourth and quite recent application of isinglass is to heal ulcerous and persistent lesions. It has been tried for healing wounds that have not responded for months to conventional treatment.

Coming back to food, fish maw soup is a Chinese delicacy just like bird nest and shark fin soups. In 2013 American smugglers were caught with 529 dried bladders of the Mexican endangered Totoaba. Consignments of fish maw derived from Mexican waters to China is said to be harming other marine lives too like the vaquita which are tiny porpoises.

Dried fish bladders are sold in Malaysian shopping malls. One can even buy these organs online. India exports dried fish maws of Eel/Vilanku/Vam, Jew fish/Kathalai/Ghol, Thread fish/Kala/Dara, Giant crocker/Panna/Kote/Kooth, Cat fish/Kelru/Petara/Singala, Bekti/Giarto perch/Waigeu sea perch, and Lizard fish to Hong Kong and other countries.