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Ecological Aquaculture

Giving Our Seas a Break

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Giving Our Seas a Break

Source:Chien-Tong Wang

A milkfish farm in Kaohsiung has found success with ecological aquaculture, using mostly all-natural feed. Its experience has raised hopes that eco-friendly fish farming can maintain supplies while allowing our exhausted seas to catch their breath.

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Giving Our Seas a Break

By Kwangyin Liu
From CommonWealth Magazine (vol. 616 )

Under a radiant sun in coastal Mituo District in the northern part of Kaohsiung, several small water birds stop at a pond to enjoy its clean water. Not unusual until one realizes that the pond is used to raise milkfish and Pacific white shrimp.

“That there are so many birds that come and drink the water indicates that it is really clean,” Tsai Hung-ching, the fish farm’s owner, says proudly.  

Mituo is an important center of milkfish farming in the Kaohsiung area, with more than 300 hectares devoted to the business, but it’s telling that none of the other fish farms in the area draw birds to their ponds.   

The facility run by the 42-year-old Tsai is rather small by Mituo standards, his two ponds covering an area of about one hectare. Tsai, who has been farming a mix of milkfish and Pacific white shrimp (also known as whiteleg shrimp) for 11 years, got into the business to make good on his late father’s wishes.

Tsai’s father ran a fish farm of up to nearly 15 hectares in Tainan, just north of Kaohsiung, when grass shrimp cultivation was at its peak in the 1980s. But the natural environment then began to deteriorate, and grass shrimp died off in large quantities for reasons that were never pinpointed, leading to heavy losses.

Tsai’s father then began raising Pacific white shrimp on a smaller scale, but he was hospitalized with ailments caused by overwork and never recovered, eventually dying without returning to his business.

The younger Tsai, who was only in his early 20s at the time, admits that when he first took over the family business, he had no idea what he was doing. It was only after fumbling around on his own and getting help from feed vendors that he learned the trade.

One day in his fourth year running the fish farm, Tsai suddenly observed many tiny plankton flying around in his pond. When he asked elders in the aquaculture business what they were, they told him it was “live bait.” Not satisfied with the answer, he sought out a book on cultivating natural bait and discovered that the organisms were algae-eating “water fleas,” small planktonic crustaceans that form a natural part of the Pacific white shrimp’s diet.

Tsai began to think that if he could cultivate more of this and other forms of “natural bait,” he could reduce the amount of shrimp feed he was using, and its high protein would benefit the health of the shrimp he was raising.

Building Natural Resistance

That inspiration led Tsai to immerse himself in the world of ecological aquaculture and steered him toward practices that have clearly differentiated his fish farm from others in the area.

In reading about eco-friendly techniques, Tsai learned about rice bran fermentation. It’s a process that over a week to 10 days allows live bacteria to extract nutrition from rice bran and creates water rich in nutrients and beneficial bacteria that are easy for water fleas to absorb.

Typical aquaculture farms toss about 3 percent of the body weight of their fish and shrimp in feed into their ponds, but the feed that is not consumed sinks to the bottom and can adversely affect the quality of water, making it easier for the animals to get sick.

The concoction also attracts other forms of natural bait. Two large round plastic drums next to Tsai’s cultivation ponds that started with the nutrient-rich water now teem with maggots in much darker water, the result of flies laying their eggs in the drums to take advantage of the nutrients there.  .

“These maggots have a lot of nutrients. They are about 70 percent protein and are really good for shrimp,” Tsai says with pride while holding up a bunch of Pacific white shrimp, which are translucent, a sign of good health.  

Typical aquaculture farms toss about 3 percent of the body weight of their fish and shrimp in feed into their ponds, but the feed that is not consumed sinks to the bottom and can adversely affect the quality of water, making it easier for the animals to get sick. In contrast, live bait thrown into the ponds for shrimp to eat does not harm the water if not consumed.

Tsai says that since he started cultivating his own natural bait, he has cut his use of shrimp feed in half and his use of fish feed by about 30 percent, generating big savings in cost.

His fish and shrimp have also benefited by being more resistant to disease and natural elements. When Taiwan was hit by a severe cold wave at the beginning of 2016, many milkfish were unable to resist the low temperatures and died, and Mituo fish farmers scrambled around the clock to harvest and save as many milkfish they could. Tsai, however, slept soundly “because I was very confident in the ability of my fish and shrimp to resist the cold.” His confidence was well-placed; his operation suffered almost no losses.

In adopting the use of natural bait to raise his fish and shrimp, Tsai had a greater principle in mind than simply lowering costs. He hoped to promote a sustainable aquaculture philosophy, believing that the bigger the reduction in total inputs used in cultivation, the better it would be for the environment.

Eco-friendly but Still Hard to Survive

In traditional aquaculture ponds where fish and shrimp are less resistant to disease because of the poor water quality caused by excess feed, the response has been to treat the water with copper sulfate and copper acetate to kill bacteria and keep the shrimp and fish from developing parasites. But deposits of the resulting copper ions also build up in the ponds and harm the health of their aquatic residents.

When asked why he has put so much effort into ecological aquaculture, Tsai answers with a question of his own. “I absolutely had to do things better than the traditional way for people to be willing to look forward. Otherwise, what’s the point of technological advances? Aren’t they there to make our living environment better than before and allow humans and animals to be healthier?”

Today, many of Tsai’s fish-farming neighbors who are decades older than him have adopted his ecological aquaculture methods. “They’ve given me a lot of face,” he says with a laugh.

Huang Chi-yang, an associate professor in National Taiwan Ocean University’s Department of Aquaculture, is a fan of Tsai’s approach. Huang says ecological aquaculture involves balancing organisms, water and the environment, and any efforts in that direction are positive. He acknowledges, however, that it is difficult to survive using this approach in a market dominated by large-scale commercial operations. 

Yet Tsai’s approach may eventually become a necessity.   

Aquaculture the Trend of the Future

It has almost become a deep-rooted stereotype that many consumers prefer wild or freshwater fish over farmed fish, but aquaculture is likely to play an increasingly important role in providing humans a sustainable source of protein.

According to a report titled “The State of World Fisheries and Aquaculture 2016” issued by the Food and Agriculture Organization of the United Nations, capture fishery production has been relatively static from the mid-1990s to the present at about 90 million metric tons while the supply of farmed fish has risen steadily. From 1980 to 2010, global aquaculture production rose nearly 12 fold, representing an annual growth rate of 8.8 percent.

If there wasn’t aquaculture to support fish consumption, we would not be able to continue to enjoy inexpensive but consistently good aquatic products

Even more revealing, the report said, was that the aquaculture sector’s contribution to the supply of fish for human consumption overtook that of wild-caught fish for the first time in 2014, after accounting for only about 10 percent of the total in the 1980s.

“If there wasn’t aquaculture to support fish consumption, we would not be able to continue to enjoy inexpensive but consistently good aquatic products,” National Taiwan Ocean University’s Huang says.

He explains that ecological aquaculture takes different forms and can involve different combinations. For example, clams can be raised together with gracilaria (a type of red algae) and Pacific white shrimp, while abalone can be farmed with sea urchins. These symbiotic relationships between organisms help reduce resource waste and improve the quality of aquatic products, Huang says.

But while ecological aquaculture may be the trend of the future, the scale of production of operations like Tsai’s remains too small to have a discernible impact on the market, says Chen Shiu-nan, a professor in National Taiwan University’s Institute of Fisheries Science. If Taiwan is really serious about expanding the scale of eco-friendly aquaculture and benefiting more fish farmers and consumers, Chen says, it should bring in experts in the field to set up a comprehensive environmental management system.

“Aquaculture around the world has now entered a new realm,” he says, explaining that for environmental management to support the expansion of eco-friendly aquaculture’s economic scale, scientific methods and standardization are a necessity at all levels, including in oxygen management, water quality management in ponds and the use of microorganisms.

Even then, Chen says, Taiwan faces a big challenge because of the country’s limited land area. Only 13,000 metric tons of Pacific white shrimp are produced a year from the 1,500 hectares devoted to the crustacean, an amount only able to satisfy one-seventh of Taiwan’s annual consumption, with the rest imported. If production is recklessly expanded, the professor says, it will lead to serious environmental pollution.

As a result, Taiwan’s aquaculture sector should not only move toward ecological aquaculture but also consider embracing environmental management, using scientific methods to boost aquaculture production and preserve the environment, Chen suggests.

That might not be just good advice for Taiwan but also the rest of the world. With fish catches along coastal areas around the globe on the decline and aquaculture production steadily rising, conservation efforts should go beyond practices to limit the consumption of wild-caught fish. They should also include applying circular and sustainable principles to farm-raised fish to ensure a future with a steady supply of fish and a cleaner environment.   

Translated from the Chinese by Luke Sabatier


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