Ganggul means “river oyster” and refers to the oysters (Crassostrea ariakensis) that live in the brackish waters at the mouth of the Seomjin River on the south coast of South Korea. They are also referred to as beotgul, or “cherry blossom oysters,” both because they look like cherry blossoms lying on the riverbed, and because they are tastiest in spring, at the same time that cherry trees are in bloom. These oysters are highly sought after due to their pleasant flavor and extremely large size: They can grow to 40 centimeters long, several times the length of most other oysters. To reach such sizes, ganggul must not be harvested until they are at least 3 or 4 years old. Their flesh is soft and has a mild, sweet and savory flavor. Ganggul are much richer in protein, minerals, and vitamins than oysters harvested farther out in the bay, and are an excellent source of the amino acid taurine, which lowers blood pressure and is important for cardiac function. Eating ganggul is good for the skin and for general health and energy. In addition to being eaten raw, ganggul are steamed, grilled, and added to rice porridge.
Although oyster farming is a large industry in Korea, ganggul cannot be cultivated: Divers harvest them by hand from the wild, at depths of 3-4 meters. Ganggul are available in local restaurants when they are in season, from February and April. They are not consumed during the breeding season, which begins in May. Until recently each harvester typically collected up to 400 kilograms of ganggul every season, but in the past few years the ganggul population has declined dramatically due to habitat loss and environmental change. Much of the land around the mouth of the Seomjin River is being developed for agriculture and industry, and sea level rise has led to increased salinity in the lower reaches of the river, which ganggul cannot tolerate.