How many generations after us will enjoy the delights of seafood? With man taking 70 million tons of fish and marine products each year from the sea, the threat of overfishing has become a real one. Taiwan, among other places, has turned to fish farms in part to combat the problem, but this solution is costly and has adverse effects on the coastline's soil and water ecology.
Which is partly why scientists have hit on the idea of sea ranches. "Preserving resources isn't opposed to progress; it's a way of making sure that the resources last," says Professor Lin Yao-sung of the Zoology Department of National Taiwan University.
Moreover, in the 1970s several countries expanded sovereignty over their coastal waters to the 200-mile limit, much to the chagrin of many long-distance fishing nations. Fishing in one's own waters started to make more sense. In 1982, when Chang K'un-hsiung of the Academia Sinica sounded the call for a national effort in sea ranches, he met an enthusiastic response from many quarters, among them being the Academia Sinicia, the College of Marine Science and Technology, and the Taiwan Fisheries Research Institute. These various agencies in turn split up the responsibilities and areas of the project.
"Sea ranching uses the many techniques of aquaculture to bring all kinds of fish and shellfish together in one place, and then feeds them in the most economical way possible," explains Chang succinctly. The fish and foodstuffs had to be selected with great care, to create a natural environment where the different species could coexist as they do in other parts of the ocean.
Located off Hsiyu Island, part of the P'eng-hu Islands, the ranch from the surface appears to be 24 six-square-meter tanks floating on the water. Three to four meters below them extend large nets, full of lively grouper, red porgy, and black porgy.
Between the tanks hang strings and strings of oyster shells, their surfaces crowded by oyster larva. The larva need a firm place on which to grow and flow with the current until they find a suitable location. At the project's outset, a square reef was constructed, then well stocked with algae to attract shrimp and crab, which would in turn draw other fish and shellfish.
The sea ranch is composed of three layers. Every few days foodstuff is distributed. Later, the uneaten scraps and body waste from the fish float to the middle layer, where they become dinner for the oysters and other fish from afar who by now know the area as a good feeding ground. Their scraps and waste then drift to the bottom layer, to serve as food for the invertebrates and the small fry, completing the sea ranch's food chain.
The group opted for P'eng-hu for several reasons. The area has clean, unpolluted water, from which 80% of the islanders make their living, and the Taiwan Fisheries Research Institute maintains a branch there. In addition, the coastline is rich in fish fry.
Statistics say that not one fry in a hundred survive to be a full-grown fish. The reasons are several, including insufficient food, environmental change, and lack of a spot to hide from predators.
To improve the odds for fry, the sea ranchers constructed an artificial reef for the sea floor. Since the 1950s, ocean scientists have gradually come to learn that fish and shellfish particularly enjoy congregating in sunken ships, which allow them to hide from their pursuers or sleep in the nooks and crannies. The reef made for the sea ranch was made of concrete and dotted with many holes to allow for easy entrance and exit. Chang K'un-hsiung has been pushing for reef construction since 1973, and already twelve have been built, which have helped boost the income of Taiwan's fishermen.
Selection of the site required careful planning. The floor had to be hard enough to withstand the pressure of over one hundred one-ton pieces, but not too deep, either. Otherwise, the reef would catch no sunlight, meaning algae would not grow well and fish would not come to visit. The final spot was located about 20 meters below the surface.
The initial inhabitants of the reef were algae and coral. After about one or two months came small shrimp and crabs, followed by bigger fish, making the reef into a bustling little village. The scientists, however, were unsatisfied, and began growing horsetail algae to quicken the process of "urbanization." Found in the belt between the tropical and sub-tropical zones, horsetail algae has long been a favorite of fish, being rich in nutrients and easy to hide in. Unfortunately, last year the ocean floor cracked under the strain of the reef, burying over half of it and preventing the horsetail algae from growing as it should.
The scientists, for their part, remained undaunted. They had already completed a phase of the project and continued experiments with artificial reefs and horsetail algae elsewhere. What did aggravate them were flatworms.
To fish for oysters, P'eng-hu anglers hang uneven lengths of cord from styrofoam to attract the larva as they float with the current. Flatworms follow the oysters to the cords, and claim annually about 10 percent of the catch. The scientists had no problems the first two years, harvesting almost a million tons. The first two months of the third year also went smoothly, but after the fourth month, scientists began opening oyster shells and finding the animals inside completely consumed by flatworms. "Just say they took no prisoners," says one oceanographer.
According to one theory, two years ago researchers said that the area's oysters had been contaminated, which caused them to drop quickly in value. Fish farms stopped harvesting the oysters, which attracted huge numbers of flatworms, some of which later invaded the sea ranch.
How flatworms open the shell and consume the oyster remains a mystery. To prevent another flatworm invasion, scientists are first soaking the oysters in heavily salted water. The results in the laboratory so far have been encouraging, but this technique has yet to be tried at the sea ranch.
While the second and third layers may seem to offer the most trouble, the first layer yields the greatest income, reportedly nearly NT$1 million (US$25,000). The nets must have holes large enough to let the fry and the currents pass through easily, but not too large as to allow the fish to escape. Initially the holes may be quite small, expanding later as the nets are replaced to account for the fish as they grow in size.
Most of the fish grown in the top layer are grouper, red porgy, and black porgy, prized for their high economic value. Raising these valuable species is made considerably more difficult by their propensity to change sexes as they mature. For example, red porgy are female until they reach 20 kgs, when they become males. Few reach that weight under natural conditions, however, and workers at the sea ranch carefully feed and pamper the fish, hoping to speed up the sex change and obtain the sperm to fertilize the eggs.
Future plans include enriching the resources of the first layer, and the sea ranch has already tried with abalone and kuruma shrimp fry. Two years ago, the kuruma shrimp catch off P'eng-hu was unusually good, but the ranch refuses to take any credit. "Pure coincidence," says Chang, "it shouldn't have happened so fast. There still is so much we don't understand well enough. We have to study how the Japanese do large-scale investigation before we can go further."
Yet as the fishing grounds off Taiwan increasingly show the effects of overfishing and pollution, seas ranches assume greater importance. Some point to this method as being the foundation of a future "Blue Revolution," but whether this revolution succeeds depends to a considerable extent on events on land as well as those at sea.
[Picture Caption]
With no need to worry about food or shelter, tropical fish explore the artificial reef.
As the fish grow, their nets must be replaced by larger ones.
Sea Ranch
(1)Six-square-meter tank for raising grouper, red porgy, and black porgy, the fish with highest economic value.
(2)Strings of oysters hang up to 13 meters below the tubs.
(3)5-13 meters below the surface swim fish of all kinds.
(4)Artificial reefs supplied with algae provide a home for invertebrates and attract fish in search of food.
(5)A special reef is set aside to raise abalone.
Harvesting oysters is a tiring but enjoyable job.
Twenty-four neatly arranged tanks float in Takuoyeh Bay. The building in the distance is the Taiwan Fisheries Research Institute P'eng-hu station.
"Raising fry is an important part of sea ranching," says Liu Chi-yuan by a tank loaded with fry.
(1)Six-square-meter tank for raising grouper, red porgy, and black porgy, the fish with highest economic value. (2)Strings of oysters hang up to 13 meters below the tubs. (3)5-13 meters below the surface swim fish of all kinds. (4)Artificial reefs supplied with algae provide a home for invertebrates and attract fish in search of food. (5)A special reef is set aside to raise abalone.
As the fish grow, their nets must be replaced by larger ones.
Harvesting oysters is a tiring but enjoyable job.
Twenty-four neatly arranged tanks float in Takuoyeh Bay. The building in the distance is the Taiwan Fisheries Research Institute P'eng-hu station.
"Raising fry is an important part of sea ranching," says Liu Chi-yuan by a tank loaded with fry.
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