Before grilling oysters for the Mid-Autumn Festival, first learn about oyster farming methods in Taiwan, China

The Mid-Autumn Festival is approaching, and grilled oysters are one of the must-have ingredients for many families grilling meat and admiring the moon. However, this year Chiayi oysters were hit hard by Typhoon Soudelor, and Penghu oysters were damaged by "flatworms," with losses of at least fifty percent. This Mid-Autumn Festival, oysters are scarcer and pricier than in previous years, so friends who want to eat grilled oysters had better hurry and grab some early.

Oysters, o-a, and hao all refer to the same thing. Penghu suffers from flatworm damage year after year, but although Yunlin-Chiayi is likewise a major oyster region, flatworm damage is rarely seen there, and the key lies in the farming method.

At present, Taiwan's oyster farming methods fall into four major categories: "stick-insertion style," "hanging style," "horizontal-hanging style" and "floating-rack style." The first three are all farmed in the intertidal zone, where the oysters can be fixed and exposed to sunlight at low tide, so flatworm damage is relatively low. They are mainly concentrated in the west.

Oysters in the "floating-rack style" soak in deep sea water for long periods and are rich in nutrients. Although they therefore grow fast and plump, their living area overlaps with that of flatworms, and since they stand still like wooden figures, it is hard for flatworms not to eat them.

Floating-rack oysters can be further divided into longline hanging and vertical hanging. The former uses thick ropes to connect styrofoam floats horizontally, then hangs several strings of oyster shells from the thick ropes below; this is the method used in Penghu.

The latter mostly uses bamboo to build a grid shape, with styrofoam underneath to float near shore, and oysters are hung vertically directly below the bamboo; most floating racks in Yunlin-Chiayi-Tainan use this method.

Although Yunlin-Chiayi-Tainan also uses floating-rack farming, the density is lower, and Lin Chin-jung, director of the Penghu Marine Biology Research Center of the Fisheries Research Institute, said that in the west the oysters are not hung as deep as the 8 to 10 m in Penghu, because the water is shallower and the water temperature varies more, which flatworms dislike.

1. "Stick-insertion style":

The earliest method: oyster shells are tied directly onto bamboo strips split in half, which are inserted on the beach to let oyster spat attach naturally. It saves cost and labor, but growth is slow and efficiency is low. Few people use it now, and it remains almost only in Kinmen, but mostly it is not the main income.

Another older farming method in Kinmen is the "stone-bar style," very similar in concept to stick insertion, except that the bamboo branches are replaced with long strips of granite rock, allowing oyster spat to attach on its own. The oysters that grow are smaller, but the flavor is very fresh and delicious.

Stick-insertion method: oyster shells are strung directly on bamboo. Because efficiency is low, it is rarely seen now (image source: Lieyu Observation Notes)

Stone-bar farming, a farming method unique to Kinmen, uses granite to naturally attach oyster spat; it is not commonly seen now either (image source: Lieyu Observation Notes)

2. "Horizontal-hanging style":

Bamboo is used as the base posts, plus two rows of crossbars, and strings of oysters are hung parallel between the crossbars. It is suitable for relatively shallow intertidal beaches, about one meter or so. In Fangyuan and Wanggong in Changhua, farmers can still be seen driving ox carts to harvest horizontal-hanging oysters at low tide.

Horizontal-hanging farming, also in the intertidal zone, is suitable for places where the water is relatively shallow, about one meter or so (image source: Yongsheng Ocean)

Horizontal-hanging farming, also in the intertidal zone, is suitable for places where the water is relatively shallow, about one meter or so (image: Yunlin-Chiayi-Tainan National Scenic Area)

3. "Hanging style":

Again, base posts are first erected, and then bamboo or plastic pipes are used above to build a rectangular grid, with strings of oysters hung vertically, perpendicular to the current, increasing feeding opportunities. The seawater in the farming areas is deeper than for the horizontal-hanging style, mostly in inner bays and tidal channels.

Hanging-style farming: at low tide the oysters are exposed above the water, mostly along the southwestern coast, where the seawater is deeper than for the horizontal-hanging style (image source: Yongsheng Ocean)

Hanging-style farming: at low tide the oysters are exposed above the water, mostly along the southwestern coast, where the seawater is deeper than for the horizontal-hanging style (photo: Ho Hsin-chieh)

4. "Floating-rack style":

1. Yunlin-Chiayi-Tainan area

Bamboo is built into a grid shape, oyster shells are hung vertically, and styrofoam is placed underneath to increase buoyancy, with more added according to the oysters' growth rate. Mostly in deepwater areas, the oyster shells soak in seawater 24 hours a day, growth is fast, and fishermen drive small rafts out to harvest.

Because some farmers directly discard waste styrofoam blocks at sea or on the beach, and styrofoam easily breaks into tiny particles, this has caused environmental controversy in recent years. The Tainan City Government is trying to guide farmers to fill styrofoam blocks directly into plastic bottles to extend their service life.

Grilled oysters in Qigu, Tainan are deeply loved by the public. (photo/Lin Hui-chen)

Floating-rack farming, a more common floating-rack method along the southwestern coast, with bamboo built into a square grid and styrofoam underneath to float on the water surface, with oysters hung below (image source: Lin Yu-kai)

2. Penghu area

Styrofoam is used directly as floats, connected horizontally in the middle with thick ropes, and then several strings of oyster shells are hung vertically from the thick ropes. Also called longline farming, the hanging depth is deeper than in Yunlin-Chiayi-Tainan, reaching as high as a 3-story building. It is relatively more vulnerable to flatworm damage.

Floating-rack farming, using styrofoam to float on the water surface and hanging oysters about 3 stories high, commonly seen in Penghu (image source: Yongsheng Ocean)

Oysters in the water

(This article thanks Yongsheng OceanPenghu Guo Family OystersLieyu Observation Notes

(This article was funded by the Jianzhen Environmental Education Foundation specifically for personnel expenses, but it completely does not interfere with news topic selection or interview writing, ensuring news independence.)