Saving Fish, Saving Ecosystems: Tzeng Chyng-shyan’s Fish Ladders

Wildlife corridors help migratory fish species make their way home. Humanity must begin addressing the needs of other living things and the environment as a whole, with a focus on properly managing aquatic environments. (photo by Kent Chuang)

Wildlife corridors help migratory fish species make their way home. Humanity must begin addressing the needs of other living things and the environment as a whole, with a focus on properly managing aquatic environments. (photo by Kent Chuang)

One of the debates swirling within the philosophical circles of a thousand years ago was whether a person could know if a fish was happy. Now, scientific research is offering a fish’s-eye view of the question. Tzeng Chyng-shyan, a professor in the College of Life Science at National Tsing Hua University whose research covers fish taxonomies and ecological engineering, has applied a fish’s perspective to the problems of helping migrating fish get past hydraulic engineering works and enabling terrestrial crabs to cross roads. His work has marked him as a pioneer in ecological engineering methods and river conservation in Taiwan.


At the beginning of each month, a group of National ­Tsing Hua University students can be found standing waist-deep in the middle reaches of Hsinchu’s Touqian River. They are conducting an ecological survey at the Long’en Weir fish ladders. This involves checking the water temperature, flow rate, dissolved oxygen levels, and pH, as well as netting small fish, which they identify, weigh and measure before releasing. Pointing to a fish shaped like a small airplane complete with “wings,” ­Professor Tzeng Chyng-shyan tells us: “That’s a loach goby [Rhyacichthys ­aspro] that has swum more than ten kilometers upstream from the ocean to get here. Seeing it in the middle reaches of the Touqian River means that the wildlife corridor is working.”

Thinking like a fish

Tzeng says that river management is a three-tiered process. Standing by the weir, he explains that the first tier is flood control, which usually involves constructing tall embankments, such as the nearby levee, to contain rising waters. The second is water usage. Taiwan’s water resources vary with the season. Check dams and wiers ensure that we have water for agricultural, industrial and residential uses throughout the year. These two stages benefit people, but take no thought for the needs of other creatures that rely on the river habitat.

Fortunately, with the recent rise of environmental awareness, the public is finally listening to advocates for eco­logical conservation. This has led to the third tier: constructing fish ladders and implementing other en­viron­mental engineering methods that help migrating fish species get past dams and weirs and return upstream to mature and breed.

The wildlife corridors next to the Long’en Weir on the Touqian River are a case in point. Tzeng and Professor Shunroku Nakamura were personally involved in planning the construction of their fish ladders, making sure that the design of the steps accounted for fishes’ need to rest. Gazing with satisfaction at the fish periodically leaping up one of the ladders as we chat, Tzeng explains that the baffles (walls) between the pools of the fish ladder are contoured: each has a taller part and a lower part. Where the baffles are lower, the water flowing over them is deeper and flows more quickly. Where they are taller, the opposite is true. This enables the fish ladder to meet the needs of fish of all kinds: small fish swim over the taller parts of the baffles, where the water is shallower, while bigger, more powerful fish swim over the lower parts, where the water is deeper. ­Tzeng’s team had conducted ecological surveys at the site over many years prior to construction, and had learned that more than 30 species of fish and shrimp lived here. “If you want to make a ladder that all kinds of fish can use, you have to think about it from the perspectives of many different fish.”

Part of a system

Although there are currently 300-some fish ladders on Taiwan’s rivers, Tzeng regards most as failures and offers a blunt assessment of the cause: “The builders considered the needs of the fish from a human perspective.”

Tzeng explains: “Fish ladders are part of a system, not stand-alone structures. They require holistic planning.”

One common problem is that fish are unable to find the entrance to the fish ladder. Another key issue is the design of the steps—they might be too tall for fish to leap from one to the next, or the water might flow too rapidly, or there may be too few rest zones.

Preliminary ecological surveys are important because they indicate which fish species will use the ladders and which predators must be accounted for, allowing designers to tailor the “user interface” to the habitat. Standing beside the Long’en Weir, Tzeng points to an egret atop the weir. “There are a lot of intermediate egrets in this area. Their legs are so long that the water has to be at least 35 centimeters deep to prevent them from simply standing in the ladder to prey on the fish.”

For all that Tzeng is very comfortable discussing the details of environmental engineering projects, he is first and foremost a recognized expert in fish taxonomy.

Tzeng has devoted his life to saving ecosystems by building fish ladders that let fish find their way home. (photo by Kent Chuang)

Tzeng has devoted his life to saving ecosystems by building fish ladders that let fish find their way home. (photo by Kent Chuang)

Gone fishin’

Tzeng likes to pun that he’s a “gone fishin’” (idle) professor. As a child, he wanted to be a motorcycle mechanic, but ultimately majored in oceanography at university. In graduate school, his advisor recommended that he specialize in freshwater fish, a direction that ultimately led to him visit all of Taiwan’s major rivers. There aren’t many freshwater-­fish researchers, and the work can be grueling, requiring treks into rural areas and deep into the mountains to gather data. Tzeng’s own experience includes a 26-year census of the Formosan landlocked salmon (Onco­rhynchus masou formosanus), which involved researchers swimming face down in the freezing water of the Qi­jia­wan River in Shei-pa National Park every year in wetsuit, snorkel and goggles, to count the fish.

Tzeng originally pursued fish taxonomy—he wanted to determine how many species of fish inhabit Taiwan’s rivers, and to understand their phylogenetic relationships to species in nearby regions such as mainland China, Japan, and the Philippines. His basic methodology involved identifying species by their morphological features, including their scales, skeletons, and fin rays. But when he began his PhD program, he chose to work with Huang Ping-chien, an academician at the Academia Sinica, who taught him how to compare DNA sequences of different species to understand their phylogenetic relation­ships and the genetic distance between them.

Tzeng went on to sequence the complete mitochondrial genome of the tasseled-mouth loach (Formosania lacustre), becoming the first scholar in the world to do so for a fish species.

Acting as a bridge

“Taxonomy is primarily an academic pursuit,” says Tzeng. “But after so many years in the field conducting surveys, I knew that the number of fish species in rivers was dropping, and that inappropriate hydraulic engineering projects were causing ecological damage.” The fact that engin­eers don’t understand ecosystems and ecologists don’t understand engineering made it difficult to forestall environmental catastrophes. But then Tzeng happened to meet Professor Shunroku Nakamura, a key figure in the modernization of fish ladders in Japan. Nakamura told him, “We ichthy­olo­gists have to be able to explain to engin­eers how to think about engineering projects if they are to avoid damaging the environment.”

Nakamura began to teach Tzeng about technical drawing, surveying, and fluid mechanics, all of which play a role in fish-ladder design. Tzeng also learned how to talk to engineers, and observed fish-ladder design projects in other countries. With many years of experience under his belt, he has enjoyed consistent success with his fish-ladder designs and renovations, which include those at the Long’en Weir, on the Niulan River in Guanxi Township, and at the Douliu Weir on the Qingshui River in Yunlin County.

The 65-year-old Tzeng recently requested that his retirement be postponed. He explains that he’d like to continue to contribute by training interdisciplinary professionals to whom he can pass the torch with confidence. “Taiwan has a ser­ious lack of interdisciplinary experts. As a case in point, not many people who research fish taxonomy also understand hydraulic engineering.”

Life finds a way

Tzeng is happy to share all of his more than 35 years of fish ladder experience. He has even traveled to China’s Qinghai Province to teach ­Tibetans about fish ladders, helping hundreds of millions of fish travel upstream ­every year to spawn.

But Tzeng hasn’t limited his focus to fish. When designing the Long’en Wier fish ladders, he also took note of the Touqian River’s mitten crabs (Eriocheir hepuensis). His study of their activity cycles and movements led him to incorpor­ate rows of grooves and ropes along the fish ladders’ curtain walls to enable the crabs to crawl past the weir.

In 2017, Tzeng won a grant from the Keep Walking program that took him to Pingtung’s underprivileged Manzhou Township. The area is known for its abundant terrestrial crabs, but the proliferation of roads has been causing massive slaughter of the crabs when they migrate from inland areas to the coast to spawn in the summer and fall. Tzeng took his students with him to Manzhou and led them through the whole process of designing, assem­bling, observing and monitoring a system of wildlife corridors for the crabs. Tzeng’s work on the project led National Geographic magazine’s Taiwan edition to honor him as one of its three 2017 “explorers.”

In 2018, the Kenting National Park Administration hired him to create similar wildlife corridors for terrestrial crabs along the coastal Provincial Highway 26 in Kenting. Tzeng used canvas walls and culverts to create very successful “crab corridors,” but the effort was halted in mid-2019. Sighing as he recalls the project, he says: “Every attempt has imperfections. There’s always something that can be improved. We have to learn from our experiences, not give up entirely.” He adds that many fish species need their own wildlife corridors. “If you know of a fish species in need, you have to address that need and work hard to make the infrastructure a success. That’s the only way to truly resolve these issues.”

Having spent so many years studying fish, Tzeng often finds himself moved by them. “They’re truly amazing!” He relates the old story of Chiang Kai-shek finding inspiration as a child in watching fish swim upstream against a strong current. “I once visited President ­Chiang’s hometown in Zhejiang Province to consult with local fish experts, who confirmed the phenomenon. Unfortunately, pollution has pretty much brought it to an end.”

In fish, Tzeng has observed a spirit of striving and perseverance. In Tzeng, we have similarly seen an eco­logist passionate about the natural world and tireless in his pursuit of knowledge.