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Stone Weirs of Penghu Islands


By Li Mingru
Photo by Li Mingru et al
Translated by Paul Stephen (USA)

Stone Weirs of Penghu Islands

There is a type of ancient man-made structure sprawl over the shores of Taiwan’s Penghu Islands (澎湖列岛): stone weirs. From the sky, the scale of these weirs is massive and their shapes complex—like mysterious calligraphy etched into the sea by some enormous hand. Adding to the mystery, these stone weirs are not limited to Penghu: similar structures appear in Japan, South Korea, the Hawaiian Islands, and even Africa and the Americas. But what are these stone weirs? Why do these identical structures appear in distant locations scattered across the world?
Penghu Islands・Baisha Village
In the picture, the beautiful “necklace” is in effect a stone weir in Penghu Islands, an ancient and mystical fishing construction. The heart-shaped pendant is the “weir-room” for catching fish, while the winding string of the necklace is the stone dam used to prevent the fish from escaping.
To children, picking seashells, starfish and crabs brought by the tide is by far their favorite activity on the beach. In ancient times, our ancestors did the same. Moreover, to “expand the victory”, they constructed a fishing device that takes advantage of the tides and the local conditions of seaside—the stone weir.

Mysterious Lines on the Shores of Penghu

During the summer, when the waters of the Taiwan Strait are a deep azure, a passenger on a flight passing over Penghu will be surprised to notice that the dark blue surface of the water is etched with bold black lines—incomparably huge—which dwarf the tiny fishing boats scattered along their sides. The lines take the complex form of arcs and spirals, such that one can clearly see the hallmark of human construction. Are these calligraphic lines the totem of some long-forgotten ancient tribe? What could be the possible significance or function of such structures?

I went to work in Penghu in 1999, thus getting a chance to examine these mysterious lines up-close: long dikes constructed from basalt rocks blended with coral reefs—and covered with oysters, barnacles, common limpets, and countless other shelled organisms. On closer inspection, I realized that these chunks of basalt were closely interlocked, without anything such as iron chains or concrete holding them together. Without any firm binding, how were these structures able to remain standing in the rising and falling tide without collapsing? Who constructed them? What was their function? Not being able to find anyone nearby to answer these questions, I was filled with doubts.

Later on, a friend invited me to Penghu’s southernmost island, Qimei (七美岛), where I found yet more of the beautiful and mysterious lines: two heart-shaped arcs and two arcs placed together, with the extremity of one arc having a half-helix curl. Viewed from afar, it had the appearance of an elegant necklace dropped to form two interconnected hearts. My friend informed me that this was the “Twin Hearts Stone Weir”, and that it is seen as a symbol of love; indeed, I saw many young couples there taking pictures, putting their hands together to form heart shapes.

“Stone weirs”: I got to know, then, the name of these mysterious lines, but still had many unanswered questions.

Penghu Islands・Qimei Village
The “Twin Hearts Stone Weir” of Penghu’s southernmost island, Qimei, is the most complete and beautiful stone weir among all those of Penghu, attracting many tourists to visit.
Photo/ Zhuang Xinxian
Penghu Islands・Baisha Village
This stone weir is an arched stone dike sitting in the inter-tidal zone. Although it has no “weir-room”, “narrow areas” with small space are built inside for catching fish, as well as a “water door” at the dick’s bottom for drainage. After the water drains, the fishermen will go down the weir for the catch.
Penghu Islands・Qimei Village
Right: Stone weirs were constructed with basalt rocks mixed with coral reefs. Although these rocks are tightly interlocked, and yet, there is nothing such as iron chains or concrete holding them together. As a result, some ancient stone weirs often require fishermen’s repair and maintenance.

Stone Weirs: The Wisdom of Tidal Fishing

In 2005, I took part in a stone weir experience event held by a Penghu local organization, where I finally learned that the stone weirs were actually constructed to catch fish. That year, due to a combination of interest and luck, I was able to embark on a series of stone weir expeditions. Hence, over the course of six years, we managed to gradually lift the veil of mystery surrounding Penghu’s stone weirs.

Stone weirs exploit the ebb and flow of the tides for fishing: at high tide, schools of fish swim into the weir, as they seek to eat the various algae, mollusks, crabs and young fish that gather in the weir’s crevices. With the arrival of the low tide, the water levels drop and the walls of the weir rise out of the water. The fish find it difficult to escape and are trapped within the weir; at this point, fishermen can catch the fish with seines, obtaining a bumper harvest: “When we land a big catch, the weir is filled mostly with fish; one can walk through, as there isn’t much water.” To this day, many old people of Penghu continue to praise the wisdom of that ancient and mysterious achievement. “The weir at Chima Village (赤马村) once caught a great shark weighing over 400 jin (a Chinese unit of weight; 1 jin = 1/2 kilogram); the shark was chasing a large amberjack fish and crashed right through the weir. Those stone weirs at Jibei Island (吉贝屿) or Chikan Village (赤崁村) sometimes would catch over 10,000 jin of Japanese anchovy and Chinese paddle-fish.”

From 2005 to 2010 my research team conducted investigations into Penghu’s weirs. Our results confirmed that, distributed amongst Penghu’s 320-kilometer coastline (excepting those areas where harbors or depth render construction impossible), there are around 600 different stone weirs. Moreover, due to differing factors such as shape, orientation, and tidal currents throughout the Penghu Islands, the farther one travels towards the northernmost extremity, the wider the tidal zone becomes, and the greater the number of stone weirs become, with each item displaying a unique shape and design.

Penghu has three main categories of stone weir: arched weirs, single-room weirs, and double-room weirs. Normally, the arched weirs sit close to the shore, located in shallower waters, and are thus often called “shallow-plain weirs”, with “plain” indicating their having been smoothed into an abrasion platform by the waves of the intertidal zone. Due to their shape, they are also known as “dustpan weirs”. Heart-shaped weirs are often called “weir rooms”. These types of stone weir are often constructed in locations that are quite far from the shore; owing to their deep water and remote locations, they are also referred to as “deep weirs” or “outer weirs”. The primary function of the weir rooms is to collect fish, and they often hold the deepest water of any part of the weir. Hence, as the tide recedes, the fish have no choice but to swim into the “weir room”. In order to prevent the fish from swimming out of the stone weirs, the arched stone dike that links the weir rooms (locals call them the “stretched leg”, with reference to the “leg” of the weir rooms) often has a half-curved spiral at its end—fish swimming along the stone wall are thus re-directed back towards the center of the weir.

The length of the dikes of the Penghu stone weirs range from 10 meters to several dozen meters, some of them surpassing 100 meters. The larger dikes often surpass 200-300 meters in length, with some even surpassing 500 or even 1000 meters; the “great weir” of Hongluo Village (红螺村) approaches 3 kilometers in total length. The height of the weir dike walls is directly proportional to the water’s depth: typically, they make up 80% of the level of high tide, such that the height of the dike decreases as it gets closer to land—normally between 1 and 3 meters. The thickness of the weir dike walls is generally similar, around 1.8 meters, though of course some of the largest weir constructions have dike walls whose thickness surpasses 2.5 meters.

When constructing a weir, one must first choose an appropriate site for collecting stone materials; then, the stones must be chiseled into suitable sizes. In order to withstand the wind and waves, the stones generally weigh between 15-25 kilograms, with some of them weighing over 50 kilograms. The stone materials are subsequently taken to the shore, and loaded onto bamboo rafts or fishing boats, where they are transported to the construction location at high tide. When the tide begins to ebb, the stones are moved into the right place, and their positions adjusted with the aid of ropes and iron tools, and fitted smoothly together in interlocking form. Smaller rocks and pieces of coral are wedged into the weir’s crevices. Because coral is mainly comprised of calcium carbonate, it reacts chemically with the seawater to form calcium hydrogen carbonate, which acts like an adhesive, fusing the stone materials together. Over time, oysters and other shelled organisms attach to the weir, further adding to its strength. There are some other small details one must be aware of when constructing a stone weir—namely, the outer side of the weir’s wall should have a curved shape to better resist the force of the waves, while the inner side should be tall and vertical, to prevent the fish from escaping.

Compared with netting or poisoning fish, the use of stone weirs has an incomparably positive impact on the preservation of marine ecology. Stone weirs follow the rhythm of the tides in collecting fish; unlike the use of nets, there is no danger of overfishing. The stone materials used to construct stone weirs are entirely natural, without concrete or other man-made substances and chemicals that can contribute to water pollution. Moreover, the inside of these weirs is actually a vigorous breeding pool for various marine life forms, including young fish, crabs, and shrimp. Finally, the construction of these stone weirs not only contributes to the preservation of marine life, but also acts as a wave breaker, helping to stem land erosion.

Penghu Islands・Baisha Village
In the photograph, the “Baisha Stone Weir” is a single-room weir. Its design of the two “stretched legs” on both sides is adapted to the local topography, making its whole structure complete. In the distance, there are several shallow-plain weirs located in the shallow water of the abrasion platform in the inter-tidal zone.
In the sunset, during the ebb, a fisherman is working in a stone weir with a flashlight in his hand. Compared with the stone weir of Penghu, this one is quite simple, but it has the same capability of fishing as those of its fancy counterparts, bringing desirable catch for the owners.
Photo/ Feng Mubo
French Polynesia
There is an ancient stone weirs group in the lagoon near Maheva Village of French Polynesia that is still in use today. These stone weirs all carry the same trait: There is always a small straw hut near the weir for the owners’ convenience of observing and catching.
Photo/Pierre Lesage
The United States
A V-shaped stone weir stands in the center of a river in New York State, U.S.A. This type of stone weir can withstand the impact of the current, leading the fish into an enclosed area where the current is relatively slow.
Photo/David Doubilet

Distant Coincidences

As my research into Penghu’s stone weirs deepened, I realized that this phenomenon was certainly not limited to Penghu alone. In fact, similar fishing structures are found all over the world—weirs are an ancient construct of hunting and fishing everywhere! When did this method of fishing actually arise? There is still no full consensus on the issue, but evidence suggests that weir fishing might have existed since the Stone Age.

I found stone weirs very similar to those in Penghu in many other places, such as in Japan, South Korea, Fiji, Australia, New Zealand, the Hawaiian Islands, Micronesia, Melanesia, and Polynesia. Even more surprisingly, in a museum in Ottawa, Canada, I saw a nineteenth-century photograph showing Eskimos making use of small stone dikes to divert salmon into shallow pools, where fishermen were then able to catch them with spears—clearly a stone weir.

In addition to stone ones, many fish weirs were wooden structures. Archaeologists have found over 200,000 wooden artifacts in the mud of Boston’s Back Bay, indicating that the area was home to many fishing weirs as early as 5,300 years ago. In Vancouver’s Cowichan River Basin, the Native American living areas in North America’s eastern region, and in the English coastline, one can find wooden weirs; while South Africa’s Kosia Bay, Tunisia’s Gulf of Gabes, as well as Benin and other West African countries are home to “shrimp weirs” made of palm trunks. On the mainland of China, in Vietnam, Thailand, and other Southeast Asian countries weirs made of bamboo can often be found.

But why have so many different places, separated by oceans, mountains, and thousands of miles, produced such similar fishing methods? Current academia has put forward two main theories. The first is that this technique arose out of the development of humans in similar environments; through observation and study, humans came to learn that weir fishing was a survival technique. With similar environments and similar goals of survival, the same method of fishing managed to evolve independently in many different places.

The second theory, in turn, contends that fish weirs arose out of mutual study and cultural propagation. Evidence shows that, despite superficial changes, the underlying design of all weirs is fundamentally the same and follows the same basic principles—especially those in the coastal regions of Austronesia, which display mature stone weir skills and the same method of managing the use of the weirs. Indeed, many places in the Pacific Islands have the same weir management system as is used in Penghu: a joint-stock system is adopted, with mechanisms to share and care for the poor. Although the headmen of Hawaiian villages controlled most of the fish weirs, the people were able to determine their own share of the weir’s catch based on the amount of labor they put into it. The headman was no exception to this rule, as he was required to do his part to maintain the weir, along with the rest of the community. Without reference to mutual study and cultural dissemination as their common origin, these similar phenomena are hard to explain.

Dr. Nishimura Asahitaro of Japan believes stone weirs are a unique element of the fishing culture that is connected with the coral reef ecosystem. The route of its cultural dissemination has been in place since ancient times—from Polynesia to Melanesia, then to the Philippines, Taiwan, and other islands of the Western Pacific, and finally to the islands of Okinawa and Kyushu. However, world-famous scholar Jared Diamond, in a 2000 article discussing Austronesian language migration, put forward the theory that, starting 5,500 years ago, Austronesian language and culture began to spread from Taiwan to the East Pacific. With Diamond’s proposed Austronesian migration route in mind, I realized that the distribution area of stone weirs almost perfectly overlaps the route of Austronesian migration. Thus, it is highly probable indeed that the skill of stone weir construction followed the Austronesian migration path. And, following this, Han Chinese migrating to Penghu simply improved upon the pre-existing foundation of stone weirs.

In addition to those made of stones, bamboo and wooden fish weirs can also be found throughout the world. In Tunisia, fish weirs are commonly constructed with palm trunks.
Photo/Charles Lenars/c
South Africa
The Kosi Bay in South Africa is a perfect site for viewing fish weirs. The wooden fish weirs here bear great resemblance to the stone weirs of Penghu Islands, which usually have a double-hearted shaped enclosed area along with a ring or a necklace.
Photo/Richard Du Toit/c
A local man is approaching the stone weir, ready to spear the fish with the stick in his hand. Using stone weirs as a fishing method might had originated during a certain period of the Neolithic Age. On many Pacific islands, stone weirs are symbols of aboriginal culture.
Photo/ Jack Fields/c

A Symbol of Survival and Culture

Constructing stone weirs inter-tidal zones that can resist wind and waves—and even typhoons—often requires spending huge amounts of time and labor. The “concave weir”, farthest off the northeastern coast of Jibei Island, is 700 meters in total length, and took over more than a decade to build. Hence, constructing a stone weir would have often required the labor of an entire clan, community, or whole village; and the subsequent management and operation of a weir would be a vital matter for the entire community. Also, the amount of fish caught depended on the weir’s position, technology, scale, and even supernatural powers. Thus, the fishing, maintenance, distribution, inheritance, pledge mechanisms and even rituals of the community revolved entirely around the stone weir, which took on religious connotations, with villagers worshiping the weir and praying to the specific gods and the religious faith that grew out of it. The stone weirs held life together for fishing societies, becoming an important feature of coral island culture.

Before the advent of machine-powered ships, the residents of Penghu had to depend entirely on the stone weirs to make a living. Without access to a weir, they could not prosper or hope to marry. In those days, betrothal gifts and conditions for marriage were often assessed on the basis of the ownership of shares in a stone weir. Due to the great benefits of the stone weir, a workable administrative system became critical. A system of taking daily shifts in labor, and a lottery system were developed to control the central weir “rooms”: winners of that day’s draw gained access to all the catch in the center of the weir “room”, while the others had to make due with whatever fish they could catch within the remaining space. The time period between lotteries was different for each village, and was often organized around ceremonial dates. Although the number of shares in the stone weir was determined by the amount of investment and size of the labor pool, there was a certain amount of “public shares”, often owned by the temple, ancestral hall, or at times the whole village, aimed at the care for the weak, or the building of other public facilities.

In modern times, due to the ever-increasing population, the demand for fish catch increases by the day. The traditional method of waiting idly for the fish to arrive now seems outdated; this, combined with technological innovation, skilled labor, and innovative equipment has meant the abandonment of stone weirs. Yet, as a cultural remnant and a “living fossil” of fishing civilizations, these mysterious lines etched into river basins and sea coasts will forever deserve our admiration, protection, and treasuring.

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