April 11, 2008

Prawn farming destroys Philippine fish nurseries: expert

As prawn farming created many Filipino millionaires, it might have also indirectly accelerated the destruction of fish nurseries in the country, according to experts.

Zoologist Jurgenne Primavera, whose research on breeding the black tiger prawn became a manual that revolutionized the Philippine aquaculture industry, said cutting of mangroves to allow the flow of brackishwater for prawn culture has affected the country's ecological systems. Mangroves are trees that grow on marshy coasts and serve as vital nurseries for the young of open-sea fish species.

Amid cheap government loans and generous land leases in the 1970s, prawn culture failed to reach its full potential, where ponds turned out to be better suited for growing milkfish, said Primavera of the Philippines-based Southeast Asian Fisheries Development Centre.

Primavera said mangroves were cleared for prawn farming in countries that did not have a long tradition in aquaculture such as Thailand, Vietnam and Ecuador.

Thriving at or near the mouths of silt-laden rivers and estuaries, mangroves have roots that serve as lungs allowing them to thrive in saline and waterlogged soils. These trees serve as nutrient-rich marine nurseries for juvenile fish, shrimp and other wildlife and as habitats or wintering areas for coastal and migratory birds, and they protect shores against storms and large waves.

According to marine biologist Norman Duke, one of the world's foremost mangrove ecosystem expert from the University of Queensland, a third of world's mangrove forests have been wiped out in fifty years due to aquaculture or fish farming. The Philippines' loss has been up to 80 percent.

Subject to volatile market prices and ecosystem degradation, prawn farms last only for a few years and abandoned farms are virtual wastelands, said Nico Koedam, a University of Brussels botanist who has done extensive research in Sri Lanka, India and Kenya.

Koedam said mangrove losses are happening mostly in Southeast Asia, India and Sri Lanka.

Duke said once conversion is done, there is no turning back as the soil dries out and "nothing will grow on it."

The Food and Agriculture Organization projects marine capture of fish is flattening out at 86-87 million tonnes annually between 2004 and 2030, and with aquaculture accounting for a progressively rising share in total fish production to 74 million tonnes in 2015 from 45.5 million tons in 2004.

Despite the rapid loss of mangroves, the International Union for Conservation of Nature (IUCN) denotes the Philippines as the "center of the center" of marine ecosystem diversity.

Primavera said the country remains one of the world's top 15 nations in terms of fish production but it will unlikely retain its position with the permanent loss of natural fish nurseries.

The Philippines is home to about half the world's mangrove species, but Primavera said up to two varieties are in the IUCN's "red list" of critically endangered species.

At least two more Philippine species could join the list this year, said Kent Carpenter, the IUCN's global marine species assessment coordinator.

Primavera explains a healthy coastal ecosystem needs four hectares of mangroves for every a hectare of fishpond.

She estimates the Philippines mangrove cover at about 115,000 hectares, compared to 230,000 hectares of fishponds.

Despite Philippine laws that bans mangrove clearing since 1975, she said enforcement has been virtually nil.