Improve Marine Aquaculture Conditions Before It’s Too Late

Current marine aquaculture conditions deplete seas and oceans of life-supporting nutrients. Find out what changes need to be made in order for marine life to thrive in and out of these fish farms.


| September 2012



The Ocean Of Life

In “The Ocean of Life,” author Callum Roberts explores the history of mankind’s exploitation of the seas, including the impact modern fishing techniques, pollution and climate change, and reveals what it would take to preserve world’s waters for future generations.

Cover Courtesy Viking

The first time water rushed onto your toes, your feet buried in the sand, you couldn’t imagine the magnitude of the ocean or all that it held. In Callum Roberts’ vibrant book, The Ocean of Life (Viking, 2012), take a fascinating tour of the history of mankind’s relationship to the sea, from the course of currents first discovered by Benjamin Franklin to the effects of shrimp farming in present-day China. In the last 20 years we have transformed the oceans beyond recognition — and not for the better. Find out how current marine aquaculture conditions harm coastal ecosystems and what we can do to prevent further damage. This excerpt is taken from Chapter 16, “Farming the Sea.” 

The explosion of marine fish farms across the world has transformed coasts, estuaries, and deltas in dozens of countries. China has pursued one of the most aggressive aquaculture development programs of recent years. In 2003, marine aquaculture covered nearly six thousand square miles, about half of China’s twenty-thousand-mile coastline. Most of these farms were carved out of mangrove forests, mud flats, salt marshes, and sea grass beds. Satellite photographs of the Bohai Sea coast, one of the most intensively farmed regions, show the toll taken. Straight-edged ponds incised in blue and turquoise pack the coast to depths of a couple of miles inland, and crawl seaward across mud flats. The Philippines and Vietnam have lost three quarters of their mangrove forests in the last few decades, half of them to aquaculture. Sadly, many of these ponds have been abandoned. When mangrove soils are exposed to the air, they become acidic. The acid leaches into pond water together with toxic quantities of aluminum, so the ponds cannot be used unless they are lined.

Mangroves and salt marshes are self-repairing buffers that defend coasts against storm and flood. If they remain healthy, there is a good chance they could also ameliorate the worst effects of sea-level rise by trapping sediment and building upward. In many places aquaculture has not only removed this benefit, it has caused the land to sink by sucking freshwater from belowground to create brackish ponds for shrimp and milkfish.

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

Tiger prawns are much favored for their large size and rapid growth, but they represent a tiny fraction of wild shrimp fry. Most wild prawn fry are caught by night lighting in shallow water under a moonless sky. Within minutes, netters are surrounded by a confusing buzz of hundreds or thousands of tiny animals, fish and fry, all drawn to the light like moths to a flame. For every individual tiger prawn caught in Malaysia and the Philippines, several hundred fry of other species are wasted. Half of the hundreds of millions of tiger prawns grown in Bangladesh are from the wild. The waste doesn’t stop at other shrimp species either. In one study, scientists found that every tiger prawn fry collected cost the lives of up to hundreds of finfish fry and over a thousand other animals that live in the plankton.

The wetland grab in developing countries has robbed the poor of the common lands from which they once eked a living by fishing and gleaning. Aquaculture provides jobs and income for some of the displaced. But the divide between rich and poor has grown, and their quality of life suffers with every waterway blocked, every forest tree felled, and every pint of pond sludge pumped into the sea. In several countries, such as Bangladesh, Thailand, and Honduras, some of those bold enough to protest the injustices have been murdered to quash opposition.