“Demon-Head Knives” and Sustainable Fishing

If you visit Xingang Fishing Harbor in Taitung County’s Chenggong Township, you can see the mahi-mahi with your own eyes. Its body is colored bright silver-yellow and blue-green, and on freshly caught fish the silvery scales still glitter with a golden-yellow hue. It is easy to distinguish male fish from female, since the head of the female is rounded and streamlined while that of the male is square and looks like the head (tou) of a demon (gui). Seen from the side, its body is shaped like a knife (dao).

“Knives” laid out on the ground

At ten minutes after noon, there is a hubbub of voices at Xingang Fish Market, and when the sound of a whistle sings out, it’s time for the auction to begin. Catches of mahi-mahi landed in the harbor since early in the day have been sorted by weight and laid out in rows of large, medium-­sized, and small fish. This market, which belongs to the Xingang District Fisher­men’s Association, still uses the traditional auctioning method, and the auctioneers here call out the prices clearly: “85, 86, ….” Watch carefully and you’ll see buyers and sellers making discreet eye contact as they complete a sale with a slight nod of the head, and the buyer’s label is stuck to the catch.

In Taiwan, mahi-mahi are mainly landed by vessels working out of Xingang in Taitung, Nanfang’ao in Yilan, and Donggang in Pingtung. Most are caught in the seas off Eastern Taiwan, accounting for some 70% of Taiwan’s total mahi-mahi catch. Xingang alone accounts for 35–55% of the East Coast catch.

Chen Junming, secretary-general of the Xingang District Fishermen’s Association, notes that unlike larger fishing vessels operating out of Su’ao and Donggang, which mainly freeze their catch of mahi-mahi at sea, boats from Xingang normally only spend one or two days at sea and chill their mahi-mahi with ice, so it can indeed be called “freshly caught.”

Longline fishing is the method most commonly used to catch mahi-mahi.

Professor Wang Sheng-ping of National Taiwan Ocean University says that mahi-mahi is low in calories, with a pleasantly firm texture, and is an excellent source of protein.

It is easy to tell male and female mahi-mahi apart: The head of the female is rounded and streamlined, while the male’s is square.

Climate change

The size of Taiwan’s mahi-mahi catch plays a significant role in the world market. Before 2000 Taiwanese production of this fish ­consistently ranked second in the world, and today it still ranks fourth or fifth, with an average annual value surpassing NT$200 million.

According to the Fisheries Agency, from 2010 to 2020 Taiwan’s annual catch of mahi-mahi remained within a range of 7,500–12,000 metric tons, but in 2021 this figure plummeted to 3,100 tons.

Nonetheless, according to academic surveys of fisheries resources, as well as data from the Inter­national Union for the Conservation of Nature, mahi-­mahi is by no means threatened by over­fishing, and the IUCN categorizes it as a “species of least ­concern.”

How can this odd situation be explained? Professor Wang Sheng-ping of the Department of Environmental Biology and Fisheries Science at National Taiwan Ocean University believes that the fall in Taiwan’s catch is probably due to climate change.

“Over the past several years many fishermen have been complaining that even at peak season they can’t catch any fish,” says Wang. Since 2021, the concept of meandering movements in the Kuroshio Current has been gaining ground in Japanese academic circles. If the path of the current changes, fish will congregate at different locations than in the past, making it hard for fishermen to find fishing grounds. With the added complication of anomalous weather patterns, the problem is not that the fish do not come, but that they come later than before and to locations farther offshore.

As soon as newly caught mahi-mahi is landed, it is sold at auction in the Xingang Fish Market—it’s as fresh as fresh can be.

Unlike the auctioneers at other seafood markets, those at Taitung’s Xingang Fish Market clearly enunciate the prices, enabling visitors to readily understand the auction process.

Eco-friendly fishing methods

With rising awareness of the importance of marine conservation, in 2014 Taiwan began setting up a fishery improvement program (FIP) for mahi-mahi at Xingang Fishing Harbor. In 2015 the program profile was published on the website FisheryProgress.org.

At present this FIP, which is at the basic level, has a grade of B, indicating “good progress.” Chen Junming points out that since the FIP was adopted, the export price of mahi-mahi has risen from about NT$60–70 per kilogram to NT$140–160, thereby achieving the goal of supporting fishermen’s livelihoods.

Lin Yubin, owner of the Meet Marlin restaurant, says that mahi-mahi can be made into many foods including fish steaks, miso soup, deep-fried fish fillets, fish floss, and fish balls, meaning that the entire fish is usable.

Mahi-mahi is a significant marine resource for Taiwan, and Xingang is the harbor where a large part of the catch is landed. (courtesy of Xingang District Fishermen’s Association)

Try some mahi-mahi

“At present there is no problem of overfishing of mahi-­mahi,” says Wang Sheng-ping, who has been involved in resource surveys on this fish for many years. Indeed, the biggest problem facing mahi-mahi in Taiwan is “insufficient consumer awareness.”

As a migratory species, the mahi-mahi, which can swim at speeds of 50–70 kilometers per hour, gets a lot of exercise, and as a result its meat is lean and low in calories, is highly nutritious, and has a firm texture. However, compared to other migratory fish such as bluefin tuna, mahi-mahi is not as easy to find on traditional markets in Taiwan. Considering that over 80% of our total catch is exported to the US, mahi-mahi has always remained a relatively little-known fish here.

With progress in cold-chain logistics, along with the emergence of competing fishing grounds off Peru and Ecuador, the Fisheries Agency has been actively promoting domestic sales of mahi-­mahi in order to reduce the risk of over-reliance on the US market.

Chen Junming notes that the Xingang District Fishermen’s Association has been selling seafood under the “Kurishio of Taitung” brand online and at a sales outlet at Sanxiantai in Cheng­gong Township. They promote foods made with mahi-­mahi including fish-head casserole, mahi-mahi and scallop sauce, and fish balls, as well as gift and souvenir items including dried fish floss and fish crackers, with the hope that more members of the public will become familiar with this fish. When people visit Xingang Fishing Harbor in Chenggong or the Miaokou Night Market in Keelung they can try local specialties including mahi-mahi served with rice noodles or made into a thick soup.

Lin Yubin, owner of the Meet Marlin restaurant in Chenggong, says that all parts of the mahi-mahi are useable. One can use the head to make miso soup, pan-fry or roast the lower jaw, and prepare steamed fish steaks or deep-fried fish fillets from the body. Mahi-mahi caught in autumn are plump and fleshy, and many Japanese customers come directly to locations where they are landed to enjoy mahi-mahi sashimi, delighted at how much cheaper it is than in Japan.

As Liao Hung-chi wrote in his essay “Gui­tou­dao,” “In the sea they flicker, sometimes visible and sometimes not, and though haughty they are also acutely aware of their surroundings.” Rather than shunning them as “demon-­head knives,” why not try this aloof and shimmering fish for yourself!

Mahi-mahi with rice noodles is a common dish served for family meals. It is made in the following way:

1. Dry-fry the mahi-mahi.

2. Heat oil in a wok, stir-fry dried shrimp and shredded shiitake mushrooms, then add water or soup stock and bring to a boil. Add rice noodles and boil until noodles are cooked, then season to taste. Add shredded carrot and fish-cake slices if desired, and the fried mahi-mahi. Sprinkle with chopped celery and serve.

Dried mahi-mahi for sale at Xingang Fishing Harbor in Chenggong, Taitung County.

Deep-fried mahi-mahi pieces are even more tender than Taiwanese-style popcorn chicken.