Why are some fish and some fish products more valuable than others? While the news media focuses on trade bans in shark fins, and seahorses, the swim bladder (or fish maw) is also a prized fish part. Selling fish maw may initially appear to be a win for the fishers. However, when fish maw is believed to possess mystical qualities, the swim bladder becomes the target of a global trade network.
|Swim bladder of the Rudd Scardinius erythrophthalmus. Photo by Uwe Gille. CC-BY-SA-3.0. Source.|
Swim bladders (also called a gas bladder) are flexible-walled, gas-filled sacs that control fish buoyancy and may aid in hearing. Swim bladders are only present in bony fishes and are rarely saved in most fisheries. Fish swim bladders are high in collagen and can be turned into glues. Nutritionists maintain that collagen can reduce joint pain and treat skin ailments. Sturgeon swim bladders were turned isinglass for clarification of beer before other alternatives emerged. In some Asian cultures the swim bladder, or maw, of fishes is considered a delicacy, and dried fish maw may sell from between $20,000 and $80,000 per kilogram. Why is the price so high? Does it have special medicinal or aphrodisiac qualities? Fish maw is eaten to strengthen one’s qi, or internal energy. However, there is no evidence that fish maw is an aphrodisiac.
|Display of fish maw at Singapore festival. Photo by Too Yut Shing, Flickr|
It’s difficult to study trade in fish swim bladders because of the global nature of trade and lack of reporting. The fish species harvested for the maw product is also challenging to identify. Since 2015, the fish trading in Hong Kong introduced a new commodity code, called “maw.” Between 2015 and 2018, 3,144–3,882 tonnes of dried fish maw was imported annually to Hong Kong (Sadovy de Mitcheson et al. 2019). These dried imports had a declared value of $264–394 million US dollars.
|Largest fresh specimen of Chinese Bahaba, caught on 30 December 1993, outside Castle Peak Bay, western Hong Kong, as incidental trawler by‐catch (Sadovy and Cheung 2003).|
Fish maw is used more for its unique texture and ability to soak up other flavors. It is almost tasteless in itself. Consequently, fish maw is used in many soup recipes and often substitutes for shark fins. As a delicacy, demand for fish maw means that many fish stocks around the world may be at risk to overfishing in order to meet this demand. Depending on the fish, it may take 25-35 pounds of fish to yield a pound of swim bladder. Therefore, the most prized fish maw often comes from large fish, many of which are croakers (Sciaenidae). The Chinese Bahaba Bahaba taipingensis is a critically endangered species due to unregulated fishing and harvest of immature individuals (Sadovy and Cheung 2003).
|A porpoise, vaquita (bottom) captured as bycatch along with a totoaba in Sonora, Mexico. Image by NOAA.|
Among the imports to Hong Kong, most fish maw were large croakers (Sciaenidae), Nile Perch Lates niloticus, pufferfish (Tetraodontidae), catfishes (Siluriformes), and pike conger (Muraenesocidae). In many of these fisheries, the harvest of fish maw is unregulated. Nile Perch Lates niloticus in Lake Victoria were harvested since first introduced in the 1950s (Ogutu-Ohwayo 1990) and locals ate fried maw until the lucrative Chinese market emerged. In 2017, Uganda, Kenya, and Tanzania earned $86 million from trade in fish maw from Nile Perch. Declines of fish harvested for their swimbladders have occurred in French Guyana and the Gulf of Mexico. Without regulations, foreign fleets off Guyana throw back the fish and take only the profitable bladders. The Totoaba (Totoaba macdonaldi), a large marine fish that lives only in the Gulf of California, Mexico, is one of the most highly prized fish maws on the market. Like the Chinese Bahaba, the Totoaba can attain 2 meters and exceed 100 kg. Consequently, Totoaba is critically endangered because of the high prices. Fishing for Totoaba has been banned since 1975 but illegal fishing continues. The Totoaba fishery threatens a small porpoise, the vaquita Phocoena sinus, with extinction as it is captured as bycatch in gillnets (Bessesen 2018; Martinez and Martinez 2018).
|Bowl of fish maw soup. from Soupbelly.com|
High-valued fish may provide a lucrative revenue stream. Unfortunately, the rarity of certain fish such as the Chinese Bahaba, makes its swim bladder even more valuable. The solution may lie in raising awareness of the status of rare fishes, and the illegal and unregulated fishing to produce fish maw. Should there be a ban on trade in fish maw? That's likely overkill because of lower valued fish maw products. The maw of the most highly valued species is valued at over $1,000 (US) per kg, and often much higher (Sadovy de Mitcheson et al. 2019). Bans do not eliminate fishing when the price for the produce is so high to produce a “gold rush” mentality. The fisheries for the Chinese Bahaba and the Totoaba are easily overfished because the combination of high value of individual fish, restricted range, and spawning aggregations make fishing more of a gold rush than a sustainable enterprise.
Bessesen, B. 2018. Vaquita: Science, politics, and crime in the Sea of Cortez. Island Press, Washington, D.C. 320 pp.
Martinez, I.A., and E.R. Martinez. 2018. Trafficking in Totoaba maw. Pages 149-170 in I. Arroyo-Quiroz, and T. Wyatt, editors. Green Crime in Mexico. Palgrave Studies in Green Criminology. Palgrave Macmillan, Cham
Ogutu-Ohwayo, R. 1990. The decline of the native fishes of lakes Victoria and Kyoga (East Africa) and the impact of introduced species, especially the Nile perch, Lates niloticus, and the Nile tilapia, Oreochromis niloticus. Environmental Biology of Fishes 27:81-96.
Sadovy, Y., and W. L. Cheung. 2003. Near extinction of a highly fecund fish: the one that nearly got away. Fish and Fisheries 4:86-99.
Sadovy de Mitcheson, Y., A.W. To, N.W Wong, H.Y. Kwan, and W. S. Bud. 2019. Emerging from the murk: threats, challenges and opportunities for the global swim bladder trade. Reviews in Fish Biology and Fisheries 29: 809-835.