THE OCEAN OF LIFE by Callum Roberts“Farming the Sea” Excerpt courtesy of Viking Books

The explosion of marine fish farms across the world has transformedcoasts, estuaries, and deltas in dozens of countries. China has pursuedone of the most aggressive aquaculture development programs ofrecent years. In 2003, marine aquaculture covered nearly six thousandsquare miles, about half of China’s twenty- thousand- mile coastline. 30Most of these farms were carved out of mangrove forests, mud flats,salt marshes, and sea grass beds. Satellite photographs of the BohaiSea coast, one of the most intensively farmed regions, show the tolltaken. Straight-edged ponds incised in blue and turquoise pack thecoast to depths of a couple of miles inland, and crawl seaward acrossmud flats. The Philippines and Vietnam have lost three quarters of theirmangrove forests in the last few decades, half of them to aquaculture.Sadly, many of these ponds have been abandoned. When mangrovesoils are exposed to the air, they become acidic. The acid leaches intopond water together with toxic quantities of aluminum, so the pondscannot be used unless they are lined.

Mangroves and salt marshes are self- repairing buffers that defendcoasts against storm and flood. If they remain healthy, there is a goodchance they could also ameliorate the worst effects of sea- level rise bytrapping sediment and building upward. In many places aquaculturehas not only removed this benefit, it has caused the land to sink bysucking freshwater from belowground to create brackish ponds forshrimp and milkfish.

Ironically, the loss of these habitats starves fish farms of twothings they need most: clean water and animals to stock their ponds.Coastal wetlands draw nutrients and pollution from the water thatwashes through them. They are also nurseries for a huge variety offish and shellfish. Although disease has forced many shrimp farmersto switch to hatchery- raised fry, countless farms throughout the tropicsstill depend on wild sources to stock their ponds, despite its catastrophicenvironmental cost.

Tiger prawns are much favored for their large size and rapidgrowth, but they represent a tiny fraction of wild shrimp fry. Mostwild prawn fry are caught by night lighting in shallow water under amoonless sky. Within minutes, netters are surrounded by a confusingbuzz of hundreds or thousands of tiny animals, fish and fry, all drawnto the light like moths to a flame. For every individual tiger prawn

caught in Malaysia and the Philippines, several hundred fry of otherspecies are wasted. Half of the hundreds of millions of tiger prawnsgrown in Bangladesh are from the wild. The waste doesn’t stop atother shrimp species either. In one study, scientists found that everytiger prawn fry collected cost the lives of up to hundreds of finfish fryand over a thousand other animals that live in the plankton.

The wetland grab in developing countries has robbed the poor ofthe common lands from which they once eked a living by fishing andgleaning. Aquaculture provides jobs and income for some of the displaced.But the divide between rich and poor has grown, and theirquality of life suffers with every waterway blocked, every forest treefelled, and every pint of pond sludge pumped into the sea. In severalcountries, such as Bangladesh, Thailand, and Honduras, some of thosebold enough to protest the injustices have been murdered to quashopposition.

So far aquaculture has sheltered most of us from the effects of overfishing. Throughout the developed world supermarket shelves creakunder the weight of an ever expanding range of farmed fish and shellfish. There is something for everyone if you can afford to pay: sturgeoncaviar, bluefin tuna sashimi, and oysters on the half shell tempthigh-end diners, while there are salmon and shrimp for the masses.And yet, the amazing expansion of fish farming since 1950 has comeat a terrible cost to coasts, wetlands, and shallow seas. Governmentshell-bent on foreign exchange or job creation have encouraged aquacultureheedless of warnings. It is not hard to see that it can’t go onlike this.

The drawbacks of aquaculture are such that one might questionwhether it really is the solution to overfishing. Wouldn’t it be betterto protect fish in their natural habitat? If we were to manage wildfisheries well, we might be able to increase supplies from the open seaby a third to a half. (I will come back later to how we can do this.)But a 50 percent increase falls far short of the needs of nine billionhungry people expected by 2050. So if the world aspires to a healthydiet of fish, aquaculture will be essential. Like any kind of farming,there are better and worse ways of doing it. The present blue revolutionwill need to turn blue- green for aquaculture to become a net contributorto human well- being. What would it take to do this?

Better farming practice comes in many forms. In some countries,shrimps are grown in ponds at low enough densities that nature canfeed them without the need for supplementary food. But such pondstake up more space than intensive farms, at a greater cost to wetlandsand coastal ecosystems. In the Philippines, the value of mangrove

forests is now becoming recognized thanks to the tireless campaigningof scientist and activist Jurgenne Primavera. She says, based ondecades of research, that shrimp ponds should not exceed a quarterof the area of mangrove forest if we are to preserve the ecologicalfunction of coasts. Her work has led efforts to restore forests andmove ponds behind sheltering buffers of trees, and she was hailed ahero of the environment by Time magazine in 2008. 32 (Shellfish andseaweeds can be also be cultured in natural mangrove and salt- marshchannels.) At the other end of the spectrum, experimental farms inBelize have gone for high- technology, superintensive methods. Thereshrimps are raised under covered raceways and fed on biofloc, clumpsof microbes formed around starch grains and sprinkled into the water.This reduces the need for expensive feed and helps recycle nutrientsfrom shrimp excreta, which reduces sludge production.We may need to say good- bye to the succulent predators favoredby Western consumers and rich Asians alike. Marine aquaculture willhave to learn instead from the ancient art of carp polyculture practicedin the freshwater ponds and rice paddies of Asia. We need tofind species that grow well together so that one will clean up thewaste produced by another. Some fish eat seaweed or detritus and canbe raised more sustainably than those that crave fish flesh. Mulletgrub around on the seabed for their food and might reduce pollutionproblems if farmed together with more predatory fish. Likewise, seacucumbers are considered a delicacy throughout much of SoutheastAsia and have been seriously overfished in the wild. These animals area bit like vacuum cleaners with a hole at one end where detritus goesin and a bum at the other where something that looks nearly identicalcomes out. Years ago, before I was aware of seafood problems, I tastedsea cucumber soup. I have to admit I’m no connoisseur and it felt abit like chewing on a rubber band. But the Chinese and Japanese lovesea cucumbers and it could make sense to grow them beneath pens offish to help recycle their waste.

The industry will need to work hard to raise standards and improvesustainability. I have met many fish farmers who are committed todoing just that. With their energy and enthusiasm, aquaculture couldindeed help feed the world. But there are challenges ahead. Growingshellfish has always been touted as one of the most environmentallyfriendly ways to produce seafood. Mussels, clams, and scallops feed onplankton and other organic matter filtered from the water aroundthem. They don’t need to be fed wild-caught fish and can improvewater quality. But there is a catch. They depend on their carbonateshells, and life is going to get much tougher for them, and would-beaquaculturists, as the seas become more acidic. If you are fond of musselsand scallops, you may want to think hard about what we can do toreduce carbon dioxide emissions.