Aquaculture: Fish farming

by Henrylito D. Tacio 

FOR the world as a whole, landings of marine fish are continuing to level off. This is also the general trend for most major fishing areas of the world, where fisheries have evolved from a phrase of increasing fishing effort and production to one in which production has stagnated and in some cases, declined, according to the UN Food and Agriculture Organization (FAO).

“Judging from known fish stocks and resources of traditional fisheries, the total marine catches from most of the main fishing areas in the Atlantic Ocean and some in the Pacific Ocean would have appear to have reached their maximum potential some years ago,” says the recent FAO report, “and substantial total catch increases from these areas are therefore unlikely.”

Here in the Philippines, the same story is happening. Moro Gulf fishermen used to catch 100,000 tons yearly. Now, they haul in only 2,000 tons, mostly cheap “trash fish.”   Panay Gulf and Bohol Sea yield four to five metric tons per square kilometer yearly — compared with its original potential of 15 metric tons.  And tuna catch, in General Santos, still hasn’t recovered from its 2004 record catch plunge.

According to recent study published in the prestigious Science, sea­food will be all but a memory by 2048 if surging hu­man pop­u­la­tions keep de­vour­ing fish and pol­lut­ing oceans at cur­rent rates. “Species have been dis­ap­pear­ing” fas­t­er and fas­t­er, said lead au­thor Bo­ris Worm of Dal­hou­sie Uni­ver­si­ty in Ha­l­i­fax, Can­a­da. “If the long-term trend con­tin­ues, all fish and sea­food spe­cies are pro­jected to col­lapse with­in my life­time.”

“Col­lapse” is de­fined as the catch of a spe­cies drop­ping by 90 per­cent, said Worm, one of a group of eco­l­o­gists and eco­n­o­m­ists stu­dy­ing how ma­rine bio­di­ver­si­ty helps sus­tain hu­manity. Twen­ty-nine per­cent of fish and sea­food spe­cies have col­lapsed al­read­y, Worm said. “It is a very clear trend, and it is ac­cel­er­at­ing.”

In a press statement, Worm deplored, “Whether we looked at tide pools or studies over the entire world’s ocean, we saw the same picture emerging. In losing species we lose the productivity and stability of entire ecosystems. I was shocked and disturbed by how consistent these trends are  — beyond anything we suspected.”

Fish are the “last wild meal” in the human diet. If the oceans are running low on many of humanity’s favorite fish, the solution would seem obvious: raise more seafood down on the fish farm, expanding the maritime version of agriculture known as aquaculture. After all, aquaculture has been a source of human protein for nearly 4,000 years, especially in Asia.

In recent years, aquaculture has become big business. Supermarkets in affluent countries are awash in scallops farmer-raised in China, mussels nurtured in New Brunswick and pen-reared cod from Newfoundland.

One-quarter of the world’s shrimps is raised in ponds in 50 countries, with Thailand and Ecuador leading the harvest. The Philippines is not far behind.

“The aquaculture harvest has doubled in the last decade, to 39.8 million tons, and now accounts for 30 percent of the global fish harvest,” reports Brian Halweil of the Washington-based Worldwatch Institute. “By 2020, it could produce nearly half of all fish harvested.”

Fish farming is more advantageous than raising livestock. “For every kilogram of dry feed, we get one kilogram of fish meat,” said Dr. Uwe Lohmeyer of the Deutsche Gesselschaft fur Technische Zusammernarbeit (GTZ), a German Technical Cooperation. “This is far more favorable rate than in the case of say, pigs: to produce the same quantity of pork, a farmer – given the same quality of inputs – has to provide three kilograms of feed.”

But like most technologies, aquaculture has its shares of liabilities. For one, intensive aquaculture is in itself a source of pollution, releasing excess feed and feces in semi-enclosed areas and creating overnutrification and oxygen deficiencies in waterways.

Marine scientists say farmed-fish require amino acids from other fish for growth, which are provided in the form of high-protein feed pellets made from wild fish. An estimated five kilograms of oceanic fish reduced into fishmeal are required to raise one kilogram of shrimp, representing a large net protein loss.

SeaWeb, a project of the Pew Charitable Trusts, says that aquaculture often has resulted in the introduction of non-native species. Sometimes, such species are purposely released into the local environment to grow, reproduce, and be harvested as has been done along the west coast of the United States with the non-native Japanese oyster and Manila clam.

Other species escape from more confined culture facilities. Some species associated with importer aquaculture species are unknowingly introduced. In Europe, 30 percent of all exotic aquatic species came originally from displacement by farmed stock.

Aquaculture might also endanger native fish species by exposing them to diseases that run rampant in the overcrowded and stressful conditions of aquaculture facilities. The use of antibiotics to reduce diseases in the culture systems only adds to the potential environmental problems in natural waters. If sick fish escape, they can easily spread the disease to wild fish.

Some coastal aquaculture practices permanently alter natural habitats. For instance, shrimp ponds are often constructed by cutting down mangrove habitats along tropical coastlines. This activity has been responsible for the loss of two-thirds of mangrove forests in the Philippines, more than half in Thailand, and more than a fourth in Ecuador.

“An estimated 670 kilograms in fish catch is lost of every hectare of mangrove forest that is clear-cut,” reports the Washington-based Population Reference Bureau. In the Philippines, about 75 percent of fish caught commercially spend some time in mangroves or are dependent on food chains that can be linked to these coastal forests.

Further pressure is put on marine ecosystems by aquaculture’s reliance on wild stocks. Milkfish culture in the Philippines, for instance, relies heavily on small, wild-caught fingerlings from the seacoasts.

Then, there’s the need for land and water. In most of Southeast Asia, lands usually converted into ponds are waterlogged areas and wetlands, cultivated ricelands or drylands. Water supply generally comes from irrigation canals or rainfed.

Erosion, sedimentation and siltation are also traced to the proliferation of fish cages and fishponds in shallow lakes and rivers. “Clearing of land where pens and cages are established results in increased erosion, sedimentation, and siltation,” explains Simeona Aypa of the Bureau of Fisheries and Aquatic Resources. “Water quality is also affected. Turbidity increases if fine silt is suspended in water in great amount thereby affecting growth of natural productivity.”

The industry is quick to defend itself, even while admitting environmental problems. “It’s the farmer who gets hurt first,” says Greg D’Avignon, executive director of the British Columbia Salmon Farmers Association. “It’s in his best interest to site his pens where currents and tides will wash the waste away.”

Irish salmon farmers are reportedly cleaning up their industry by reducing fish density and by letting a bay go fallow for a month after each harvest, so that its water and the sea bottom can purify themselves. “As in every livestock-rearing process, you have to look after your animals,” says Richard Flynn, executive secretary of the Irish Salmon Growers Association.

But will our fish in the wild go extinct soon? ““The good news is that it is not too late to turn things around,” Worm said. “When humans get into trouble they are quick to change their ways. We still have rhinos and tigers and elephants because we saw a clear trend that was going down and we changed it. We have to do the same in the oceans.”

Worm and his colleagues stud­ied 48 ar­eas world­wide that have been pro­tected to im­prove ma­rine biodi­ver­sity. This has proven effective in places including the Georges Bank off the U.S. Atlantic coast. With marine reserves in place, fishing near the reserves can improve as much as four-fold. He reported: “We see that di­ver­si­ty of spe­cies re­cov­ered dra­mat­i­cal­ly, and with it the ec­o­sys­tem’s pro­ductiv­i­ty and sta­bil­ity.”

The late national scientist Dioscoro Umali once pointed out: “Nature has a God-given capacity to regenerate once the hand of man is no longer raised against it.”

For nearly one billion, mostly in Asia, fish supply 30 percent of protein; worldwide, the figure is just six percent. — ###